Sawing along and across the grain. Open industrial training lesson "sawing wood along, across the grain and mixed sawing"
Methodological development open lesson industrial training:
“Sawing wood along, across the grain and mixed sawing”
Plan
open lesson on industrial training
by profession "Carpenter"
master of industrial training: Zakharova L.M.
All actions of the industrial training master are aimed at equipping students with deep knowledge, skills and abilities, the professional significance of which is necessary for future success. labor activity. The correct organization and conduct of an industrial training lesson provides the opportunity for the active inclusion of each student in production activities, as well as the cooperation of students with each other and the industrial training master.
Program topic: "Basic carpentry operations for wood processing"
Lesson topic : “Sawing wood along, across the grain and mixed sawing”
Lesson objectives:
1 . Educational: formation of techniques for carpentry operations “sawing”
2. Developmental: the ability to plan work and control one’s work
at all its stages
3. Educational: fostering responsibility and independence,
rational use of working time,
accuracy and patience when performing carpentry
operations
Lesson type : a lesson in learning new work techniques and operations
Methods, forms of lesson delivery, teaching methods used:
Verbal : instruction, conversation, explanation.
Visual : demonstration of working techniques and sawing operations
Practically e: independent work of students
Types of control:
Oral survey, practical exercises(re-showing the techniques performed)
Interdisciplinary connections :
Carpentry technology, basics of construction production,
construction graphics.
Educational and methodological equipment of the lesson :
Instruction card
A set of tests (on the topic of the lesson)
Carpentry workbenches
set of sawing tools: set of hacksaws (wide hacksaw, narrow hacksaw)
sawing equipment: miter box
measuring instruments: tape measure, ruler, square, compass
samples
blank material
Predicted result :
Formation of skills to perform longitudinal and transverse sawing and mixed sawing operations
An object : carpenter training workshop
During the classes:
Master's activity
Student activities
1.Organizational moment
1.Checking the attendance of students according to the magazine;
2. Check appearance;
3. Checking students' readiness for the lesson.
Ready for lesson
2. Introductory briefing
1. Report the topic of the lesson;
2. Communicating the objectives of the lesson;
3. Testing knowledge of previously studied material using tests:
(Appendix No. 1)
Listen and write down the topic of the lesson.
Working on tests
Studying new material according to plan:
Purpose of carpentry operation: sawing wood
Types of sawing depending on the direction of the wood fibers:
Along the fibers
Across the grain
Mixed sawing
3. Sawing tools
4. Demonstration of working techniques:
techniques for preparing saws for work
tool sharpening techniques
sawing techniques
5. Purpose and application of instructions technological maps
3. Issuing tasks
1.Issuing individual assignments
2.Communication of quality requirements for the sawing operation
Listen to the master's explanation
4. Ongoing briefing
Control of the master over the independent work of students:
Targeted walk-throughs by the master of students’ workplaces:
First round in order to check the maintenance of workplaces and compliance with labor protection and labor discipline rules;
Second round in order to check the correctness of the carpentry operation, sawing wood and the correct execution of working techniques;
Third round in order to verify the correctness of self-control;
Fourth round for the purpose of checking and evaluating the completed task
Independent work of students:
Organize workplace:
preparing the necessary tools
preparation of blanks
2. Performing techniques for sawing wood
3. Self-monitoring of the correct performance of professional techniques:
-by sawing issued blanks
- selection of tools
- self-monitoring of compliance with labor safety rules
5. Final briefing
Summing up the lesson:
Reporting results in achieving lesson goals;
assessment of the quality of each student and the group as a whole
analysis typical mistakes in the work of students
Post ratings
Listen to the master of the p/o
5.Cleaning of workplaces by students,
cleaning the workshop by the attendants
Comment
Reminding previously studied material
Quality requirements for various types of plaster.
The accuracy of the execution of various plasters must meet the requirements of SNiP or ENiR, which also determine the thickness of the plaster. The thickness of the plaster must correspond to the following data, mm: simple up to 12, On smooth brick surfaces the thickness of the plaster can be up to 10 mm,
The plaster must adhere firmly to the surface, not peel off, and without external defects. The accuracy of the plastering is checked using a rule (slat) 2 meters long.
To do this, the rule is applied to the surface at different directions: vertical, horizontal, diagonal. If the deviations turn out to be greater than the norms, they are eliminated (the solution is cut off or additionally applied).
The verticality and horizontality of simple plaster is controlled by a rule, or a cord, that is, by pulling the cord with an indentation to the thickness of the plaster. The prepared solutions are filtered. In this case, large particles remain on the sieve and the solution is additionally mixed, which improves its homogeneity.
Solutions for spraying and soil are filtered through a mesh with 3X3 mm cells; solutions for covering layers in ordinary plaster - additionally through a sieve with 1.5X1.5 mm cells.
Solutions for spraying must be stronger than for soil, since the spray holds the entire thickness of the plaster. For covering, a solution that is less durable than for soil is used.
Clay and lime mortars must have normal fat content. Lean mortars that have an excess of filler (sand), weak, greasy mortars dry out and crack, and a lot of binders are consumed for their preparation.
The fat content of the solution or binders is determined in the laboratory.
Plaster mortars must have workability, i.e. the ability to be easily laid in a thin, dense layer, filling all irregularities. This property largely depends on the mobility of the solution, i.e. the ability to spread under the influence of its own mass. Mobility is characterized by the amount of standard immersion. The steps are prepared first. Plaster the top of the walls first, then the bottom.
Purpose of wood sawing operations
2. Types of sawing (depending on the direction of the wood fibers)
-along the fibers
- across the fibers
- mixed sawing
Tools for sawing wood:
1. Longitudinal sawing (narrow hacksaws) (lesson 10)
2. cross sawing (wide hacksaws) (lesson 11)
3. curved sawing (narrow hacksaws) (lesson 12)
PERFORMANCE OF SIMPLE PLASTERING
Plastering is carried out in the usual way. First, the surfaces are cleaned of mortar deposits, a masonry joint is selected to a depth of 1 cm for better adhesion of the mortar to the surface.
In case of application with mortar pumps on wooden surfaces, the thickness of the spray should be no more than 9 mm, on stone, concrete and brick surfaces - no more than 5 mm.
The plaster solution is applied to the surface by throwing or spreading.
Simple plaster consists of two layers - spray and primer. Before plastering, the surface is moistened with water. A layer of spray is applied to the wetted surface and, after it hardens, primer is applied. Spray is the first layer of plaster coating. The thickness of this layer when applied manually is 3-5 mm.
A liquid solution is used for spraying. The density of the solution applied manually should correspond to the immersion of a standard cone within 8-12 cm. The solution of the spray layer, flowing into all the pores and roughness of the surface, adheres firmly to it and holds the subsequent layer - the soil. The more correctly the spray solution is prepared and applied, the better it will flow into all the roughness, the stronger it will adhere to the surface and the more firmly the plaster will adhere.
Throwing
The solution of the spray and the first layer of soil is always thrown in so that it better penetrates into all the roughness and thereby adheres more firmly to the surface. The second layer, primer, can be spread on.
Primer is the second layer of plaster coating. The solution for the primer is prepared somewhat thicker than for spraying. The mobility of the strained plaster solutions at the time of their application should correspond to the immersion of a standard cone: for soil without gypsum within 7-9 cm; with plaster - 8-10 cm.
The soil is the main (by volume) layer of the plaster coating. It forms the required thickness of the plaster and levels the surface.
If the thickness of the plaster is large, then the primer is applied in several layers. The thickness of each of them should not exceed 7 mm for lime and lime-gypsum mortars and 5 mm for cement mortars. The soil is leveled very well.
Throwing the solution with a spatula from the box.
Many plasterers apply mortar onto the walls with a spatula directly from the box. In this case, a lightweight mobile box and an oversized spatula are used. The technique for throwing the solution is the same as when throwing it with a spatula from a falcon. When plastering, the soil solution is often spread from the falcon. Level the solution with a falcon or trowel. For greater accuracy, the soil solution is additionally cut to a length of 2 m.
The work is carried out in this sequence.
Having prepared the surfaces of the walls, husks are first arranged. To do this, apply mortar marks to the thickness of the future plaster in the corners of the walls, walls and ceiling. A rule is attached to the marks and the solution is poured into the space between it and the wall or ceiling. Having installed a lighthouse on one side of the wall at the very corner, they begin to build a second lighthouse at the same corner. Thus, two beacons form an exact husk. This is done at all corners of the walls, as well as the walls and ceiling.
Plastering is performed in the following sequence. On one side of the ceiling, a strip of mortar 1 m wide, called a mortar, is applied. The spray and primer soil are leveled using the following rules. The same excuse is made on the opposite side of the ceiling. In the future, these excuses will play the role of beacons. A spray is applied to the remaining part of the ceiling between coatings, and soil is applied to it, which is leveled with a long trowel or a rule. These tools move with their ends along the slips, cutting off the solution at the level of these slips. The walls are plastered in the same sequence.
THROWING THE SOLUTION
During the plastering process, the solution must be applied in different positions: from left to right and from right to left. It depends on the place where the solution is applied. The most convenient position is to apply the solution from left to right.When plastering walls, apply the mortar at head level or slightly higher, at waist leveland near the floor or scaffolding. When plastering ceilings, you have to apply the mortar from different positions: over your head, over your shoulder, above you, away from you.
When throwing from yourself, the swing of the spatula and throws of the mortar are directed forward from the plasterer. When throws are made above oneself, the solution lies almost above the head, but the swing of the blade should be directed slightly to the right. If the mortar is applied over the head or over the shoulder, then the mortar is thrown behind the plasterer’s back.
When applying the mortar, you should always choose a position so as not to throw the mortar towards the plasterer working nearby and not to splash it with the mortar.
Workplace organization
The work is organized as follows. If the surface to be plastered is located below the level of the box, then it is installed at a distance of 1 m from the steppe. It is better to use a mobile solution box on wheels. It is placed close to the place of work near the walls and under the place where the solution is applied on the ceilings.
Throwing mortar
The plasterer takes a portion of the mortar from it with a spatula and throws it onto the wall. If the solution is thrown above the level of the box, then it is placed next to the wall. This allows you to reduce unnecessary movements, and the solution flying off the wall falls into the box. During operation, the box is periodically moved to the place where the solution is poured.
SOLUTIONS
When performing work, the air temperature in the room must be at least 5°C. The water and solution are heated to 10-30°C. The beginning of setting of the solution occurs after 10-30 minutes, depending on the temperature of the air and the solution. It is recommended to water surfaces plastered with this solution with water for three days.
Non-thermally conductive plasters are made from a light, quick-drying solution consisting of 1 wt. parts of cement, 1 part of lime paste, 2 parts of sand and 5 parts of asbozurite. To prepare the solution, cement, sand and asbozurite are mixed and a dry mixture is obtained, which is mixed with lime milk.
For plastering external walls
For plastering external walls, the following mortar compositions are used (in volumetric parts): 1: 2: 4 (lime: clay: sand), for internal walls - 1: 1: 4 (lime: clay: sand).
Leveling the mortar with trowels
The trowel is placed on the surface with the applied solution, the upper edge is lifted and with pressure it is carried along the wall from the bottom up, along the ceiling towards you. Where there is a lot of solution, it is cut off and collected on a grater cloth. Where it is missing, the removed excess solution is spread. In some places it is necessary to apply additional solution. To more accurately straighten the solution, they sometimes do this. First, the grater is carried out on the walls in a vertical direction, then in a horizontal direction, and on ceilings, first along the ceiling, then across. The evenness of the resulting plaster depends on the force with which the pressure is applied to the trowel or other tool. Where the pressure is stronger, the layer of solution is thinner, and vice versa. Quality checking
Often, after leveling with trowels, the evenness of the plaster is checked using a rule that simultaneously additionally levels the surface. The rule is applied to the plaster in all directions and unevenness is immediately corrected. In those places where there are recesses, apply a solution and level it.
Warnings
Violation of technical rules and regulations during plastering work and preparation of mortars leads to the appearance of various types of defects in the plaster: dents, cracks, peeling marks.
PREVENTION OF DEFECTS
Dutik is a small bump that appears on the surface of the plaster; crumbles easily, leaving a white or yellowish spot in the center.
Ducts are formed because the solution was prepared with unseasoned lime, in which small particles were not quenched. Once in the plaster, they begin to extinguish after some time and increase in volume. The suppression can last for quite a long time, sometimes for years. To avoid dummies, freshly slaked or slightly aged lime dough used to prepare the solution must be strained through a sieve with holes of 0.6 mm or 0.5X0.5 mm.
Large and small cracks appear on the surface of the plaster because either fatty (with a high content of binders) or poorly mixed solutions are used, in which a lot of binders or fillers accumulate in places. Cracks can also appear as a result of the use of thawed lime-gypsum mortars or from rapid drying of the applied plaster under the influence of strong drafts or high temperature. Cracks also form from applying a thick layer of slow-setting mortar at one time or because the mortar is applied although thin layers, but onto the previous layer of solution that has not yet set.
To avoid the appearance of cracks, it is necessary to strictly dose binders and fillers when preparing the solution and mix it thoroughly.
No more than 10% of the defrosted solution can be added to a freshly prepared solution. To avoid the appearance of cracks, it is necessary to strictly dose binders and fillers when preparing the solution and mix it thoroughly.
No more than 10% of the defrosted solution can be added to a freshly prepared solution.
Self-control
It is necessary to check the verticality of the surface using a level.
Surface horizontality using the rule
Surface diagonality using the rule
Student work evaluation indicators:
1. Organization of the workplace
2. Compliance with safety precautions and labor discipline
3. Compliance technological process
4. Quality 5. Self-control
ORGANIZATION OF WORK
Scientific organization works and jobs makes it possible to increase labor productivity. Practicing individual techniques for performing certain operations reduces fatigue to a minimum, while simultaneously increasing productivity and improving the quality of work.
To do this, it is necessary to use high-performance tools and rational techniques for performing various operations. An important role is played by the quality of the tool and the ability to handle it, the correct grip of the tool and the worker’s stance when performing the operation.
The organization of plastering work depends on many factors: the type of plaster, the surfaces to be plastered, the mortar used, the type of finishing, the scope of work, the proportion of individual operations, the composition of the team and units, as well as the qualifications of the workers.
The configuration of the links plays a big role. The team leader must be a qualified plasterer who knows how to properly organize jobs and work in general, and assign team members to perform those operations that they know best and can perform quickly and efficiently. The link leader must not only lead the link, but also work himself, providing assistance to low-skilled members of the link, if necessary, then show individual techniques execution. The quantitative composition of a unit or team depends on the complexity of the work performed.
OCCUPATIONAL SAFETY AND HEALTH
When plastering, it is necessary to strictly follow safety rules and take all measures to reduce injuries.
Rubbing of the skin of the hands can occur from improperly made tool handles. Handles must have no sharp corners or edges. The handles of all tools must be firmly secured. This protects your hands from chafing, calluses and other injuries.
When spreading the solution on the surface of walls or ceilings from a metal falcon, when pressed, the end of the spatula often breaks off the slippery metal surface of the falcon; the spatula can injure the hand holding the falcon. To prevent this from happening, you should support the tool not with the blade, but with the handle of the spatula or your hand. It is advisable to work in gloves.
It is strictly forbidden to handle mortar - lime, lime-gypsum and cement - with your hands. To avoid injury, it is recommended to pour all materials with a spatula or scoop.
Be careful not to get lime mortar or lime in your eyes.
Assignment for the day indicating the time norm and production norm for completing the work:
· communication to students of performance assessment indicators and evaluation criteria;
· distribution of students among workplaces;
· summing up the introductory briefing.
Applications No. 1
(tests)
Question No. 1.
1. List which tools are classified as plastering tools?
Correct answer:
Ladle, grater, grater, falcon, plaster spatula
2. Simple plaster consists of...?
a) one layer
b) three layers
c) two layers
Correct answer:
c) two layers
3. What is the thickness of plain plaster?
a) 18mm
b) 12mm
c) 15mm
d) 10mm
e) 20mm
Correct answer:
b) 12mm
4. What are the layers of simple plaster?
a) splash, soil, covering
b) spray, soil, soil, covering
c) spray, gunt
d) soil, cover
e) spray, covering
Correct answer:
c) splash, soil
5. What is the thickness of each layer of plain plaster?
a) spray-7mm, primer-10mm
b) spray-6mm, primer-5mm
c) spray-5mm, primer-7mm
d) spray - 3mm, primer - 8mm
e) spray - 4mm, primer - 9mm
Correct answer:
c) spray-5mm, primer-7mm
6. Name where simple plaster is used?
a) in offices, palaces
b) in residential buildings, schools, kindergartens
c) in administrative buildings
d) in basements, garages
Correct answer?
d) in basements, garages
7. What are the tolerances of plain plaster?
a) up to 5mm
b) from 2 – to 7mm
c) from 1 to 4 mm
d) up to 3mm
d) up to 6mm
Correct answer:
a) up to 5 mm
Appendix 2
BORODINO
Tell me, uncle, it’s not for nothing
Moscow, burned by fire,
Given to the Frenchman?
After all, there were battles,
Yes, they say, even more!
No wonder all of Russia remembers
About Borodin Day!
- Yes, there were people in our time,
Not like the current tribe:
The heroes are not you!
They got a bad lot:
Few returned from the field...
If it weren't God's will,
They wouldn't give up Moscow!
Sail
The lonely sail is white
In the blue sea fog!...
What is he looking for in a distant land?
What did he throw in his native land?...
The waves are playing, the wind is whistling,
And the mast bends and creaks...
Alas, he is not looking for happiness
And he’s not running out of happiness!
Below him is a stream of lighter azure,
Above him is a golden ray of sun...
And he, rebellious, asks for a storm,
As if there is peace in the storms!
Death of poet
The Poet is dead! - slave of honor -
Fell, slandered by rumor,
With lead in my chest and a thirst for revenge,
Hanging his proud head!..
The Poet's soul could not bear it
The shame of petty grievances,
He rebelled against the opinions of the world
Alone, as before... and killed!
Killed!.. why sobs now,
Empty praise unnecessary chorus
And the pathetic babble of excuses?
Fate has reached its conclusion!
Weren't you the one who persecuted me so viciously at first?
His free, bold gift
And they inflated it for fun
A slightly hidden fire?
Well? have fun... he's tormenting
I couldn't stand the last ones:
The wondrous genius has faded away like a torch,
The ceremonial wreath has faded.
Caucasus
Caucasus! distant country!
The home of liberty is simple!
And you are full of misfortunes
And bloodied by war!..
I believe: under one star
You and I were born;
We walked the same road,
We were deceived by the same dreams.
But well! - from a noble goal
Torn away by a storm of passions,
I forgot in the fruitless struggle
Legends of my youth.
Lecture 11
Sawing wood. General information
1. Characteristics of the sawing process
Sawing is the process of dividing wood with a saw into volumetric, undeformed parts by turning the volume of wood between these parts into chips.
A saw is a multi-blade cutting tool that works in a closed cut. A kerf is a gap formed in wood when teeth cut narrow shavings (sawdust). The cut has side walls and a bottom with which the blades (teeth) interact.
2. Classification of types of sawing
Sawing wood is classified according to several criteria.
Depending on the position of the saw plane in relation to the wood fibers, longitudinal, transverse and mixed sawing is distinguished.
At longitudinal sawing The plane of the saw is parallel or approximately parallel to the grain of the wood. Sawmill frames, circular saws and band saws operate on the principle of longitudinal sawing, on which logs and beams are sawed into boards, and lumber is cut to width or thickness in the longitudinal direction.
When cross cutting the plane of the saw is perpendicular or approximately perpendicular to the grain of the wood. Sawing is performed manually with cross-cut saws, hacksaws or on cross-cutting machines used for cutting logs into round logs, removing wood defects and wane areas from the ends of the lumber, as well as giving the lumber a given length and quality.
For mixed sawing the saw plane is located at an acute angle (10˚...80˚) to the direction of the fibers.
Depending on the type of saws used, there are different the following types sawing:
– longitudinal frame sawing, sawing with band, circular and jigsaws;
– cross-cutting with circular, chain and jigsaws;
– mixed sawing with circular, band and jigsaws.
Depending on the number of simultaneously working saws in the machine, a distinction is made between individual and group cutting methods. Cutting logs and lumber with one saw is called individual cutting, and cutting with several saws is called group cutting.
For individual sawing logs are sawn into lumber with separate cuts on circular saws, band saws, vertical or horizontal machines. The cutting is carried out taking into account individual characteristics quality zones of each log. This cutting method is effective when sawing valuable wood, cutting large-diameter logs and logs with significant defects.
For group sawing sawmill frames, multi-saw circular saws and band saws, as well as milling and sawing machines are used.
Depending on the position of the workpiece relative to the center of the circular saw, sawing with the peripheral zone of the saw, the middle zone and the central zone of the saw, as well as sawing with the upper and lower zone of the saw are distinguished.
When working in the peripheral zone saws, the teeth of the saw protrude above the surface of the workpiece by an amount approximately equal to the height of the tooth.
When working in the middle zone saw teeth protrude above the surface of the workpiece by an amount equal to approximately one third of the radius of the saw.
When working in the central zone The center of the saw is located at the middle of the cutting height. This type of sawing is used in milling and sawing machines.
The peripheral and middle working zones of the saw can be located on the upper or lower sections of the saw, which is observed in circular saws with a lower and upper saw shaft.
When cutting logs into lumber, the following methods are used (Fig. 1):
– log collapse;
– beam collapse;
– sawing with beams into one or two beams;
– cutting out asymmetrical timber (sleepers);
– camber-segment and beam-segment;
– circular;
– sectoral.
When sawing logs waddle On sawmill frames or multi-rip circular saws, unedged boards and slabs are formed in one pass. This sawing method is often used when cutting hardwood logs.
When sawing with lumber The log is sawn in two passes. On the first pass, one or two double-edged beams, unedged boards and two slabs are obtained from the log. On the second pass, the beam is collapsed and edged boards with a width equal to the thickness of the beam, unedged boards and two slabs are obtained. In this case, the boards cut from the middle part of the timber are radial. Boards cut from the peripheral zones of the timber are tangential. The remaining boards occupy an intermediate position.
With the split-segment cutting method, on the first pass from middle zone The logs are cut into several unedged boards, and two segments are obtained from the side zone.
With the circular method of sawing logs, each subsequent cut can be directed parallel, perpendicular or at any angle to the previous one. This makes it possible to obtain radial and tangential sawn timber. The log can be sawed parallel to its longitudinal axis or parallel to its generatrix. The circular method is especially effective when cutting large-sized raw materials.
With the sector sawing method, the log is first sawed along the axis of the log into parts that have the shape of sectors in cross section. Then one block is cut from each sector, the face of which is parallel or perpendicular to the radius of the log. If the annual layers of wood are located to the face at an angle of less than 45˚, then tangential sawing lumber is obtained; at an angle of more than 45˚, but less than 60˚, mixed sawing lumber is obtained, and at an angle of more than 60˚, radial sawing is obtained.
3. Widening the cut
When sawing, the side cutting edges of the teeth deform the walls of the cut. After the teeth pass, the walls of the cut are elastically restored, the distance between them is reduced, and the saw blade can be clamped. Due to friction, the saw becomes so hot that it becomes impossible to work with it, it loses stability.
To prevent the saw from clamping, its serrated edge is widened. The width of the cut should always be greater than the thickness of the saw blade. If this condition is not met, then the walls of the cut clamp the saw.
The widening of the cut is carried out by setting or flattening the teeth, or using saws with a lateral undercut, or the saws are equipped with plates made of hard alloys, the teeth of which are sharpened with a lateral undercut.
At divorce (Fig. 2, A) the tips of the teeth with a length of 0.3...0.5 of the tooth height are bent alternately in different directions. At flattening (Fig. 2, b) the tips of the teeth are flattened and shaped, giving them the shape of blades located symmetrically relative to the saw body.
Round planing saws (Fig. 2, V), have a lateral undercut at an angle of 15¢ and 25¢.
Saw teeth with carbide inserts (Fig. 2, G) have the shape of spatulas with a lateral undercut.
The width of the cut in this case is found as follows:
Where b– cutting width, mm;
S– saw blade thickness, mm;
S’ – widening of teeth on each side, mm.
Values S’ it is recommended to use the reference book in the range of 0.2...1.1 mm. Its value depends on the type of wood (density), humidity and working conditions.
4. Specific friction force
A kerf is a narrow gap formed by a saw. Cutting chip width b falls into the cut width b P.
Due to the elasticity of wood, the walls of the cut are partially restored after the passage of the tooth. Kerf width b P< b. Thus, the chips are clamped from the sides by the walls of the cut (Fig. 3).
With further movement of the tooth, the chips overcome frictional forces F t along the walls of the cut and the front surface of the tooth, is pressed into the interdental cavity, gradually filling it. The longer the path of the tooth in the wood, the more chips accumulate in the cavity, the more it is compressed and rubs against the walls of the cut.
Average friction force per tooth passage in the workpiece
where a is the tangential pressure on the tooth from the friction of the chips in the cut (specific friction force of the chips on the walls of the cut), MPa.
The specific friction force of the chips in the cut is equal to the ratio of the average friction force to the cross section of the cut layer:
. (2)
The values of a for saws with set teeth al and flattened teeth aD are found from (Table 1).
Table 1
Tangential pressure a on the saw tooth due to chip friction in the cut
tape | |||
The specific friction force is the tangential pressure of the chips on the tooth, created by the friction forces in the cut.
5. Saw performance in terms of cavity capacity
Sawing performance is characterized by the amount of feed per tooth, determined by the capacity of the interdental cavity.
The sawdust formed during sawing is placed between the teeth and removed from the cut.
Based on numerous studies of cutting theory, the following formulas are recommended for calculating the feed per tooth based on filling the cavities with sawdust:
when sawing with frame saws
; (3)
when sawing with band saws
when sawing with circular saws
Where t max – maximum cutting height.
6. Thickness of the cut layer when working with flattened and set teeth
In Fig. 4 shows three cuts of the same width b, in which layers of wood are cut at the same feed per tooth S z. The first cut shows the set teeth of the saw, and the second cut shows the shapes of the layers cut by these teeth. The third cut shows the shape of the layers being cut by flattened teeth. The areas of the layers cut by set and flattened teeth are the same and equal bS z. Average feed per tooth along the length of the cutting edge 
found by dividing the cut area by the length of the cutting edge bl:
.
Usually taken
, (6)
where m is the feed angle (the angle between the directions of the feed and main movement speeds).
7. Saw tooth shape for longitudinal and cross cutting
The sawing rule can be formulated as follows: when inserting a tooth into wood, you first need to cut the fibers, and then, with the least resistance, separate them from the massif and remove the chips from the cut.
For longitudinal sawing (Fig. 5, A) the tooth with its main cutting edge cuts into the wood and cuts its fibers. The wedge of the tooth penetrates the wood and the front edge tends to press the cut chips away from the wood. Since the strength of the wood in the plane of the fibers is weak, the cut part of the chips breaks off and falls into the interdental cavity.
The saw tooth must have a cutting angle at the main cutting edge that is always less than 90°. The side cutting edges are not sharpened and are left with a cutting angle of 90°.
When cross cutting (Fig. 5, b) the work of cutting wood fibers is performed by the side cutting edges. For this purpose, the teeth are made with side sharpening. When teeth are inserted into wood to a depth of 0.8 mm, stresses at the bottom of the cut created by the beveled front edges of the teeth (Fig. 5, V), reach the limit of shear strength along the fibers and the cut fibers split either to the left or to the right along the fibers.
When cross-cutting wood, the main work is performed by the side cutting edges of the teeth, inclined forward and having beveled front edges. To ensure these conditions, the saw teeth are sharpened as follows: cutting angle at the main cutting edge d > 90 ° , and the side cutting edge is made with an oblique sharpening anglej = 40...45 ° .
Test questions and assignments
Please indicate the number of the correct answer.
1. When sawing wood circular saw, in which the thickness of the disk is 2 mm and the widening of the teeth on the side is 0.6 mm, the cutting width is equal, mm
2. Widening of saw teeth is achieved by
1) divorce,
2) flattening,
3) use of saws with side undercut,
4) soldering of plates followed by oblique sharpening,
5) increasing the thickness of the saw.
3. What is the difference between rip and cross saws?
4. How to take into account the friction of the saw in the cut in the calculations?
5. What cutting methods do you know?
K category: Carpentry work
Sawing wood along the grain
To obtain a workpiece of the required width and thickness, the board is sawed along the grain. But first, the workpiece must be marked and secured in the rear clamp of the workbench (Fig. 1).
The rules for sawing wood along the grain have much in common with the rules for sawing across the grain. But there are some differences: the working posture is slightly different, the body position is straight, the rhythm and pace of sawing is faster.
Here is the sequence of work when sawing a workpiece along the grain:
Fastening the workpiece and the carpenter's working posture.
1. Mark the cutting areas.
2. Clamp the workpiece vertically into the rear clamp of the workbench. The edge of the workpiece should not be higher than shoulder level.
3. Prepare the instrument and take the established position.
4. Make a cut along the marking line. Don’t forget that you need to hold a block, not a hand, near the bow saw blade.
5. Start sawing, observing the rhythm and pace.
Rice. 1. Sawing wood along the grain
When working, it is necessary to constantly monitor the position of the saw blade relative to the workpiece along the marking line, bench board, and ruler. Make sure that the bottom of the cut is approximately at chest level (after all, the workpiece can always be raised and lowered). Follow the rules safe work. Before the end of sawing, you need to work more slowly, without pressing, so as not to split the workpiece and injure your hands.
The quality of work can be checked using a ruler or square.
When sawing along the grain, the following types of defects may occur:
1. The cut is not straight.
Causes:
a) you did not follow the marking line;
b) pressed hard on the saw;
c) did not operate the saw during operation.
2. The cut is not at a right angle to the wide side of the workpiece.
That's why:
a) you started work not exactly at a right angle to the edge of the workpiece;
b) they cut incorrectly, not along the workbench, not according to the markings;
c) did not control the saw blade.
Remember!
To avoid defects when sawing, you must work carefully and strictly follow the established rules.
Of course, it is better to work without marriage. But if some errors still appear, do not be upset!
Disadvantages can be eliminated using a planer by planing.
Tools for work.
To cut wood along the grain, hacksaws, bow saws, and tenon saws are used (Fig. 2, a, 6, c). In such saws, the teeth are inclined and have the shape of a triangle with an acute angle (Fig. 2d). Therefore, these tools cut only in one direction, where the teeth are inclined (usually away from you). When moving backwards (towards itself), the saw does not cut the wood; it is an “idle” motion.
Rice. 2. Saws for cutting wood along the grain: a- hacksaw; b - beam; c – thorny; g - tooth shape
But very often during work there is no time (or it is difficult) to change the tool, although you have to cut the wood along the grain, and across it, and obliquely. For these purposes, saws with mixed teeth are used. The tooth shape is a right triangle with a right angle directed towards the sawing side.
Sawing technique. When sawing wood along the grain, as when sawing across the grain, the width of the cut depends on the thickness of the blade, the height of the teeth and their spread. The more you have cut, that is, the thinner the blade, the finer the teeth and the smaller the gap, the easier and faster it is to work.
Rice. 3. Sawing wood along the grain
Fix the workpiece in the clamps of the workbench and saw along the marking lines as shown in Fig. 3. The saw teeth should be tilted in the direction opposite to the hand, that is, away from you.
- Sawing wood along the grain
TO category:
Joinery
Sawing techniques hand saws.
There are three main types of sawing: horizontal along the grain, vertical along the grain and horizontal across the grain.
Horizontal sawing along the grain is used for sawing long boards lengthwise into bars with a rip saw. Long boards are not convenient for clamping in a workbench in a vertical position, so they are laid on the workbench horizontally along the lid and secured with a clamp or workbench blades. Fastening is done so that the sawn part of the board protrudes beyond the edge of the workbench (Fig. 1).
When working, hold the loose saw with both hands, as shown in Fig. 1.
The working movement when sawing with a rip saw is vertical. The position of the worker is shown in Fig. 1. The body should be slightly tilted forward and remain almost motionless when working.
When sawing with a rip saw, the saw teeth apply pressure to the material being cut. The pressure should not be great: with too much pressure, the cut may turn out to be uneven, with cuts away from the mark. When the saw moves upward, its teeth move slightly away from the bottom of the cut. If the saw is clamped in a cut, a wedge is inserted into it.
When sawing long boards, bench stands are used.
Sawing with a rip saw horizontal position material - the easiest and most productive method of sawing with hand saws.
When vertical sawing along the fibers perpendicular to the face (cutting along the width into bars and slats), the board is secured vertically with a rear clamping box; when sawing parallel to the face - with the front clamping screw. The front clamping screw is usually used to clamp small parts. The saw is held firmly by the stand with the right hand, possibly closer to the handle, and the material being cut is supported with the left hand. The saw direction is horizontal.
When cutting a board vertically along its width, its successive clamps as the cut lengthens are made in such a way that each continuation of the cut does not extend beyond the length of the shoulder part of the lowered right hand. The pressure of the saw teeth on the material being cut occurs due to the weight of the beam. You should not apply strong pressure with your hand: this makes the cutting plane uneven, the saw deviates from the mark, and the carpenter quickly gets tired.
Rice. 1. Sawing along the grain with a rip saw with the material positioned horizontally
Rice. 2. Bench stands: a - wooden on a cross with an adjustable stop: b - metal with a roller; c - wooden with roller
Rice. 3. Sawing with a bow saw along the grain with vertical clamping of the material: a - with a rear clamping box; b - front clamping screw; c - position of the feet of the worker when sawing
Sawing is done by moving the right hand. The body and left hand should be motionless, the body is slightly tilted forward. The foot of the left foot is placed parallel to the workbench, and the right foot is placed at an angle of 80° to the left foot.
Sawing is carried out to the lower end of the marks. To do this, the board is re-clamped, positioned at an angle so that you can see the line to the end. Cutting not completely risks taking into account additional splitting of the cut is unacceptable; additional splitting leads to defective parts. In the case of cross-layered wood, this defect is inevitable.
When sawing horizontally across the grain with a bow saw, the board is laid on the workbench lid so that the sawn part protrudes beyond the back bar of the lid. The edge of the board rests against the folding stop.
Holding a saw right hand hold the stand near the handle, support the material being cut with your left hand and press it against the stop. The body of the worker should be motionless and slightly tilted forward. The legs are placed as shown in Fig. 4, b.
Sawing is done by moving the right hand with slight pressure on the material with the saw teeth. Pressure is needed because sawing across the grain is the most difficult type of wood cutting. The size of the cut in this type of sawing is usually small, so it is not difficult to avoid distortion of the cut line under the influence of pressure. To ensure that the sawn part of the board (especially when it is more or less long) does not break off under the influence of its own weight and does not form a flake, it is necessary to support this part at the end of the cut with your left hand (Fig. 4, c).
Rice. 4. Sawing across the grain on a workbench against a stop: a - holding the saw, laying and supporting the material: b - position of the feet when sawing; c - supporting the sawn section
The cut, i.e. the beginning of sawing with a bow saw, is done with the saw blade directed along the line using a nail or a second joint thumb left hand. To avoid injuring your finger, you need to keep the nail or knuckle above the teeth. The cut is made by smoothly moving the saw towards you (with a rip saw - moving from bottom to top). The small depression that forms is the beginning of the cut. You cannot make a cut by jerking the saw forward: such a technique is very dangerous.
The movements of the saw when sawing should be uniform. From 60 to 80 cuts are made per minute.
The perpendicularity of the cut to the face of the board being cut is checked during work like this. Having advanced the saw to the handle, remove the hand; if the saw blade in this free position makes a right angle with the face, then the cut is perpendicular to the face. Control check done with a square after sawing is completed.
When sawing with a cutter, it is useful to first make a preliminary cut with a chisel. The work is carried out using a ruler. If sawing with a cut is carried out at an angle to the plane of the shield, it is convenient to use, instead of a ruler, a block with an edge beveled according to the inclination of the cut.
Cross cutting of planed plywood with a plywood saw is also done using a ruler. The file cuts when you move it in both directions. You should not apply strong pressure on the file.
Narrow (trigger) hacksaws are used for sawing along curved outlines. Sawing with wide hacksaws is carried out in cases where a bow saw cannot be used, for example, when cutting large sheets of plywood.
Working with adjusted tools and the right techniques allows you to save effort and time, increase labor productivity, and improve the quality of products. At the same time, operational safety is increased.
Innovative carpenters use hand saws to cut material in batches. This is how they cut the boards crosswise; longitudinal cutting of thin boards; figured sawing of thin boards; sawing down box tenons. Sawing in batches saves time on clamping the material in the workbench. It takes more time to clamp each board or part separately than to clamp the same several parts in a pack.
When sawing material in batches, you need to ensure that the saw blade is perpendicular to the face of the first board.
By simultaneously filing tenons on several parts, the tenons are more accurate and of higher quality. This is explained by an increase in the length of the cut: with a longer cut, it is easier to avoid bevel of each individual tenon, and it is easier to obtain a clean, fringe-free cutting surface. Wherein work time saves not only on laying and clamping parts, but also due to the fact that marking is simplified and the length of the cut increases.
For precise and clean cross-cutting (trimming) of parts at right angles and at an angle of 45° (miter), use a saw miter box (sawing box), shown in Fig. 5. Trimming in a miter box is carried out with a fine-toothed saw with a slight tooth set or no tooth set at all. This saw produces a clean cut and does not damage the miter box slots. The parts, one or several at a time, are placed in a miter box. During sawing, they are pressed with the palm and thumb of the left hand to the side of the miter box opposite (from the carpenter).
Organization of the workplace and safety precautions.
Besides general requirements rational organization of the workplace, which must be performed when working with hand-held carpentry tools; when sawing with hand saws, additional requirements are imposed.
The most important of them:
1. Before starting, as well as during work, it is necessary to check the sharpening condition of each saw; You cannot work with dull saws.
2. All saws that are to be used are taken to the workplace and hung on the wall, or even better, on a special board in close proximity to the rear clamping box of the workbench. You should not place saws on the workbench to avoid damaging the workbench cover. During breaks. When sawing, to re-clamp the material, the saw should be placed on the workbench from the side of the tool board and supported on the workbench with the handle and the beam stand.
3. When cleaning the saw after work, turn the saw blade with its teeth towards the spacer (inside the beam).
4. When carrying or transporting the saw over a considerable distance, turn the blade with its teeth towards the spacer and wrap it in cloth. Sometimes the gear ring, without turning, is covered with a case in the form of a wooden block with a longitudinal narrow groove for the teeth.
Most dangerous moment in working with hand saws, this is a cut when the saw blade is guided along the line using the thumb of the left hand. A significant danger is the rupture of the saw blade during operation, especially the circular saw. Prevent these dangers by being careful and attentive in your work.
Do not let the end of the twist past the beam spacer: the protruding end of the twist may get caught in the material being cut and come off the spacer. The string will unwind and the twist may fly out. In this case, the possibility of tearing the canvas cannot be ruled out.
Rice. 5. Miter box (sawing box) for trimming at an angle of 90 and 45°
Teaching students how to work with a carpenter's saw; develop hand motor skills, eye, coherent speech, correction motor sphere(motor skills, motor dexterity, stimulation of two-handed activity), develop figurative memory, logical thinking; to cultivate a thrifty attitude towards forest resources and the economical use of lumber; cultivate a positive attitude towards work.
Download:
Preview:
State government educational institution of the Krasnodar Territory
special (correctional) school No. 10 in Belorechensk
(GKOU school No. 10 of Belorechensk)
Open lesson on the topic:
« Sawing: types (across and along the grain) difference between operations»
5th grade.
Professional teacher:Danilchenko Irina Nikolaevna
Belorechensk.
2018
Outline of an open lesson using modern educational, ICT and health-saving technologies in the 5th grade, specialized labor teacher of State Educational Institution School No. 10 of Belorechensk, Danilchenko I.N.
Lesson topic: “Sawing: types (across and along the grain), the difference between operations”
Lesson objectives:
- Educational: teach students how to work with a carpenter's saw;
- Developmental: develop hand motor skills, eye, coherent speech;
- Corrective: correction of the motor sphere (motor skills, motor dexterity, stimulation of two-handed activity), develop figurative memory, logical thinking;
- Educational: to cultivate a thrifty attitude towards forest resources and the economical use of lumber; cultivate a positive attitude towards work.
- Lesson type: combined.
Forms of organization of educational activities: frontal, individual, group. - Method: explanation, demonstration, story, demonstration, independent work under the supervision of a teacher.
Equipment. Carpentry kit, miter box, blanks, presentation “Sawing wood”
DURING THE CLASSES
1. Organizational moment.Communicating the topic and purpose of the lesson.
2.Repetition of the material covered
Conversation on issues
- What tools are used for marking?
- Types of sawing wood.
- Difference between hacksaw and saw.
- Rules for safe working with a hacksaw.
Sawing - the operation of dividing wood into pieces using a saw.
Saw – a multi-cutting tool with teeth-cutters that form drank away
Theoretical information.
Based on the direction of cutting wood fibers, the following types of sawing are distinguished:
transverse (across the fibers);
- longitudinal (along the fibers);
- mixed (at an angle to the direction of the fibers).
Tooth – the main element of the saw. It has three cutting edges: one front and two side. A tooth has a base and a top, the distance between which is its height. The distance between two vertices is tooth pitch .
Used to perform various types of sawing different kinds drank.
For cross cutting, saws with straight teeth are used. The cutting edges of the tops of the teeth alternately cut the wood fibers and remove the broken wood particles in the form of sawdust.
Types of carpentry saws: a - hacksaws: 1 - longitudinal, 2 - transverse; b - bow saws: 3 - with metal and 4 - wooden frames
Before sawing Special attention attention should be paid to securing the workpiece.
A regulated hand position when sawing has also been adopted, which ensures the safe execution of this technological operation.
Before you start sawing, you need to make a cut. To do this, press the saw against the stop and make several smooth movements towards you.
Saw grip and working posture
When cross cutting
Grasp the handle of the hacksaw tightly with your right hand, place the foot of your left foot perpendicular to the workbench and on 1
/
3
under it, right - at an angle of 70 o to the left leg.
The body should be motionless, slightly tilted forward.
For longitudinal sawing
Hold the bow saw by the stand, as close as possible tohandle, left footparallel to the workbench, right - under an angle of 70° to it. The position of the body body is the same as for cross-cutting.
Physical exercise. I’ll press my two palms and swim across the sea. Two palms, friends, this is my boat. I will raise my sails and sail across the blue sea. And fish swim here and there on the stormy waves.
Basic rules when sawing:
make an incision along the line;remove the block and saw off the part;At the end of sawing, the pressure on the saw is released.
Start sawing by cutting towards yourself. For convenience, use a stop or block. When cross-cutting, the material to be cut should hang from the workbench. For longitudinal cutting, cut the workpiece to approximately the middle, and then re-fasten and saw off on the other side.
You need to cut not along the marking line, but next to it at a distance of about 5 mm. The marking line should always remain on the future part.
For precise cutting of workpieces at angles, use miter box
The miter box consists of a miter box bottom and two sides with cuts at different angles.
Sawing in a miter box increases the accuracy of sawing, eliminates marking costs, and increases labor productivity. The use of a miter box is especially effective in mass production.
For precise sawing at an angle of 45 o and 90 o a miter box is used - a sawing box. Secure it with wedges to the workbench lid or press it against the side edge.
3 . Physical education minute.I. p. - stand against the wall in the position of correct posture. After taking a step forward, maintain the pose for 2-3 seconds. Return to i. n. Check your posture. 8-10 times.
4. Instruction on safety rules when sawing
- Sawing is carried out with a serviceable, well-set and sharply sharpened saw.
- Ensure that the workpiece is securely secured
- Do not allow the saw to skew
- Sawing smoothly without sudden movements, do not hold left hand close to the saw blade
- After finishing cutting, place the saw on the workbench with the teeth facing away from you.When cleaning the workbench, use a brush.5. Practical work.Completing tasks for students of levels 1-4 is the same:
Cut out a wooden blank according to the markings. (50 by 150 mm)Cut the workpiece in a miter box at an angle of 45 degrees.
Induction training. Compliance TB when sawing with a hand hacksaw. Students take their seats and begin to complete the task.6. Current briefing.Monitoring the correctness of the practical task.
5. Fixing the material.
What can be used to securely secure the workpiece?What saw should you use to cut?Where should you hold your left hand when sawing?How to put the saw down when working with it?How and with what to clean the workbench?8. Lesson summary. Final briefing.Oral report from students about the work done.Identification of mistakes made and their analysis.Grade practical work students.Cleaning workplaces.Homework:repeat: the difference between longitudinal and transverse sawing, the purpose of a miter box, safety precautions when sawing. Reflection. Guys, what new did you learn in class today?Where can you apply the knowledge you have gained?
Used Books:
- Textbook for students in grades 5-9. Wood processing technology. Author I.A. Karabanov. Moscow "Enlightenment" 1995
- Internet resource https://site
- Internet resource . http://www.trudoviki.rf/load/glavnaja/glavnaja/samoanaliz_uchitelja_tekhnologii_stoljarnogo_dela/2-1-0-19
- Internet resource https://kopilkaurokov.ru/