Carpentry and Joinery by 9N9T3x

VIEWS: 26 PAGES: 21

									  Carpentry and Joinery
Module 4: Machinery and Joinery
  Unit 2: Rip Sawing
          (Circular Saw)
         Phase 2
Carpentry & Joinery – Phase 2                                        Module 4

                                                 Table of Contents
List of Figures .................................................................................................................... 4

List of Tables ..................................................................................................................... 5

Document Release History ............................................................................................... 6

Module 4 – Machinery and Joinery ................................................................................ 7
   Unit 2 – Rip Sawing (Circular Saw) ............................................................................... 7
    Learning Outcome: ..................................................................................................... 7
    Key Learning Points: .................................................................................................. 7
    Training Resources: .................................................................................................... 8
    Exercise: ...................................................................................................................... 8
    Key Learning Points Code: ......................................................................................... 8

Circular Saw ...................................................................................................................... 9
   The Cutting Process ...................................................................................................... 10

Saw Blades ....................................................................................................................... 10

Circular Saw Safety ........................................................................................................ 10
   Why Unguarded Saws are Dangerous .......................................................................... 10
   Circular Saws Guards ................................................................................................... 11
   Guard Adjustment ......................................................................................................... 13
   Riving Knife ................................................................................................................. 14
   Cutting .......................................................................................................................... 15
   Push-Stick ..................................................................................................................... 16
   Use of Push-Sticks ........................................................................................................ 17
   Clearing Away and Taking Off .................................................................................... 18
   Logs and Firewood ....................................................................................................... 19
   Grooves, Rebates and Tenons ....................................................................................... 19

Self Assessment................................................................................................................ 20

Index ................................................................................................................................. 21




Unit 2                                                                                                                                  3
Carpentry & Joinery – Phase 2                                 Module 4

List of Figures
Figure 1.    Circular saw .................................................................................................... 9
Figure 2.    Cutting process.............................................................................................. 10
Figure 3.    Circular saw safety........................................................................................ 10
Figure 4.    Circular saws guard....................................................................................... 11
Figure 5.    Circular saw guards....................................................................................... 12
Figure 6.    Circular saw guard adjustment...................................................................... 13
Figure 7.    Riving knife .................................................................................................. 14
Figure 8.    Riving knife fixed to saw bench ................................................................... 14
Figure 9.    Cutting........................................................................................................... 15
Figure 10.      Push-stick diagram 1 ................................................................................. 16
Figure 11.      Push-stick diagram 2 ................................................................................. 16
Figure 12.      Use of push-stick....................................................................................... 17
Figure 13.      Clearing away and taking off .................................................................... 18
Figure 14.      Logs and firewood .................................................................................... 19




Unit 2                                                                                                                          4
Carpentry & Joinery – Phase 2   Module 4

List of Tables




Unit 2                                     5
Carpentry & Joinery – Phase 2        Module 4

Document Release History

 Date                      Version              Comments

 October 2006              V.1.0.




Unit 2                                                     6
Carpentry & Joinery – Phase 2                   Module 4

Module 4 – Machinery and Joinery
Unit 2 – Rip Sawing (Circular Saw)
Duration – 6.5 Hours
Learning Outcome:
By the end of this unit each apprentice will be able to:
        State the purpose of a rip-saw (circular saw).
        Identify and state the names of the various parts of a circular saw.
        Identify correct method of operating locking levers and devices.
        Identify and define correct position of safety guards.
        Operate circular saw safely (under supervision) using push stick when cutting
         materials.
        Identify and describe correct Tungsten Carbite Tipped saw blades when cutting
         different types of materials.
        Summarise wood working regulations related to rip-saws.
        Identify hazards, apply safe working and house keeping practices.
        Record the process of operating a ripsaw.
Key Learning Points:

 RK        Purpose of rip saws.

 RK        Parts of rip saw.

 RK        Method of operating locking levers and devices.

 H         Safety guards.

 SK        Safe cutting of materials/push stick.

 RK        TCT saw blades.

 RK        Woodworking machine regulations.

 RK        Housekeeping.

 H         Identification of hazards/circular saw.

 RK        Safe work practice.

 P         Information gathering on rip saws.

 P         Report writing P.




Unit 2                                                                                   7
Carpentry & Joinery – Phase 2                Module 4

Training Resources:
    Hand fed circular saw.
    Extension rest.
    List of questions.
    Push stick.
    Safety handout.
Exercise:
Complete exercises in this document.
Key Learning Points Code:
M = Maths             D= Drawing       RK = Related Knowledge Sc = Science
P = Personal Skills   Sk = Skill        H = Hazards




Unit 2                                                                       8
Carpentry & Joinery – Phase 2                 Module 4

Circular Saw
Circular saw set in a flat bed with an adjustable fence to gauge the width of cut or “rip”.
Used for cutting narrow strips out of wider material. With a tilting fence cuts at other
than 90° can be made.




                                Figure 1.      Circular saw
Important Note:
Every machine is provided with guards for the protection of workers. These should
always be in the correct position and must not be removed unless the machine is
immobilised.




Unit 2                                                                                        9
Carpentry & Joinery – Phase 2                Module 4

The Cutting Process
The material being cut is fed past the revolving blade. This method is suitable for both
ripping and cross-cutting.




                              Figure 2.      Cutting process
Saw Blades
Refer to Unit 1, Cross Cutting for information about Saw Blades.
Circular Saw Safety
Why Unguarded Saws are Dangerous
Most fatal accidents to wood machinists happen when a whole piece is erected by the saw
under one or other of the circumstances shown overleaf. In addition, accidents can occur
at unguarded saws through the machinist slipping, or reaching past or over the saw to
clear away waste and cut pieces, and coming into contact with the blade. Another
frequent cause of injury is touching the saw teeth under the bench when clearing away
waste.




                            Figure 3.      Circular saw safety


Unit 2                                                                                     10
Carpentry & Joinery – Phase 2                  Module 4

REMEMBER: USING AN UNGUARDED SAW IS DANGEROUS AND ILLEGAL


Circular saws must therefore be guarded in three ways:
1. Guards for parts below the bench.
2. A riving knife at the back of the saw above the bench.
3. A guard for the crown and front of the saw blade.




                             Figure 4.      Circular saws guard
Even with these guards fitted, circular saws are still dangerous unless agreed safe
working practices are followed. Important points about these dangers are illustrated in
these cards.

Circular Saws Guards
Refer to Figure 5; Circular saw guards. Guards should be:
        Rigid to prevent them touching the saw blade.
        Strong so that an accidental knock will not displace or bend them.
        Easy to adjust so that they can be set correctly.
        Well maintained to keep them easy to adjust, i.e. clear of sawdust, rust and dirt.
        Regularly checked so that defects like stiff handles are quickly discovered and
         rectified.
        Set to cover both sides and roots of teeth.
        Set as close as practicable to the timber being cut.
The saw should be fully guarded below the bench, so that hands cannot come into contact
with the blade when clearing away: the teeth can cause injury even when the blade is
stopped. Special guards should be considered for long production runs if this would help
to improve safety.




Unit 2                                                                                        11
Carpentry & Joinery – Phase 2          Module 4




                         Figure 5.   Circular saw guards




Unit 2                                                     12
Carpentry & Joinery – Phase 2                 Module 4

Guard Adjustment
Refer to Figure 6.
Wait until the blade is stationary before adjusting the guards - never use scrap timber to
slow the blade down. Not only can the hands slip during adjustment, but the guard itself
may touch the blade.
        Set the saw height to suit the material being cut.
        Check that the saw packing is in good condition.
        Lower the crown guard to give an adequate running clearance for the teeth.
        Adjust the guard rearwards so that the gullets of the down-running teeth will be
         covered by the extension piece.
        Check that the guard is in line with the saw blade.
Position the fence and set the extension piece as close as possible to the timber being cut.
When cutting thin timber, which could prevent the correct positioning of the guards, use a
false fence of the same thickness as the material being cut.




                       Figure 6.      Circular saw guard adjustment




Unit 2                                                                                       13
Carpentry & Joinery – Phase 2                  Module 4

Riving Knife
The riving knife should be matched to the saw blade in use. It should be slightly thicker
than the plate of the saw to prevent the wood binding, but not so thick that it makes
feeding difficult.




                                  Figure 7.     Riving knife


The knife should be securely fixed below the saw bench and adjusted as close as
practicable to the teeth of the saw. It should be not more than l2mm from the saw at the
table and should follow the curve of the saw as far as practicable.
Refer to Figure 8; Riving knife fixed to saw bench.
For a saw blade of less than 600mm diameter, the top of the knife must be not more than
25mm below the top of the saw.
For a saw blade of 600mm diameter or more, the top of the knife must be at least 225mm
above the table.




                      Figure 8.        Riving knife fixed to saw bench




Unit 2                                                                                      14
Carpentry & Joinery – Phase 2                  Module 4

Cutting
Refer to Figure 9.
If the saw is sharp, the timber should feed easily with little loss of saw speed. If excessive
feeding pressure is needed the wood may jerk or snatch and hands may come into contact
with the blade.




                                   Figure 9.       Cutting


The sound the saw makes will tell if it is blunt or being fed too fast. The pitch will lower
if the saw slows down because it has to work too hard: the wood may also judder. In
either case, partially withdraw the timber; allow the saw to gain speed and feed it again
more slowly. If the saw is blunt, it should be changed, keeping saws sharp will improve
production as well as reducing the risk of accidents due to the machinist forcing the
timber through. Saws should be regularly checked and removed for sharpening before
they get blunt. The type and size of saw and the speed selected must be suitable for the
wood being cut. Too small a saw will not cut efficiently due to the low peripheral speed.
A notice specifying the diameter of the smallest saw that can be used with the machine
must be displayed the minimum size is 60% of the largest saw that the bench will take.




Unit 2                                                                                      15
Carpentry & Joinery – Phase 2                 Module 4

Push-Stick
A suitable push-stick must be available at every circular saw and the machinist should
use it for all operations which would otherwise involve the hands being close to the saw
when it is in motion.




                           Figure 10.     Push-stick diagram 1


Push-sticks must be well made from hard wood, comfortable to use and suited to the
machinist. It is a good practice to chamfer the nose of the push-stick on one side and to
cut the bird’s mouth at right angles to the chamfer, so that a straight push can be made
with the hand clear of the fence when cutting narrow pieces.




                           Figure 11.     Push-stick diagram 2


Care should be taken to keep the nose of the push-stick from being cut by the saw, though
this is sometimes unavoidable. Damaged push-sticks should be re-cut but discarded
before they get too short to use safely.




Unit 2                                                                                      16
Carpentry & Joinery – Phase 2                  Module 4

Use of Push-Sticks
Refer to Figure 12; Use of push-stick.
Most of the accidents at circular saws occur while feeding the timber by hand,
particularly when the wood snatches or breaks. Injury is most frequently caused to the
machinist’s hands, often with serious and permanent damage.
These accidents can be avoided by using mechanical feeding systems, which should be
adopted wherever possible. Where this is impracticable, the following rules should be
strictly observed:
        Keep the hands away from the saw blade at all times. The whole surface of the
         bench should be treated as a NO-GO area.
        On production work, use the next piece of timber to feed the previous one past the
         saw. For the last piece, or for one-off pieces, use a push-stick from the edge of the
         table up to and past the saw teeth.
        Use a push-stick for clearing away cut pieces and sawdust from both sides of the
         saw.
        Where necessary, use two push-sticks, one for feeding the timber and the other for
         keeping it against the fence.




                               Figure 12.     Use of push-stick




Unit 2                                                                                     17
Carpentry & Joinery – Phase 2                 Module 4

Clearing Away and Taking Off
Refer to Figure 13; Clearing away and taking off.
The hands should never be used to clear cut pieces away from near the saw teeth.
Experience has shown that if this practice is used, then, sooner or later, a finger or hand
will be caught by the teeth, often with very serious injury.




                        Figure 13.     Clearing away and taking off


Always use a push-stick to clear material and waste from:
        The down-running teeth which are exposed when no timber is being fed.
        The up-running teeth. The edge of a cut piece may catch in the gullet and be flung
         back violently.
        The sides of the saw. Keep the hands well away as sleeves may catch in the teeth.
When another person assists the machinist in taking off cut pieces and waste, a take-off
table must be provided with its edge not nearer than l200mm from the up-running teeth.
The taker-off must stand at this position when taking off.




Unit 2                                                                                        18
Carpentry & Joinery – Phase 2                 Module 4

Logs and Firewood
Refer to Figure 14; Logs and firewood.
Cross cutting logs and scrap timber for firewood is dangerous because:
        Logs may roll or snatch during cutting.
        Logs and firewood may break suddenly when partly cut.
In either case, hands may contact the saw teeth. For safety reasons, logs and firewood
must not be cut on a circular saw except when firmly held by a gripping device fixed to a
travelling table.




                             Figure 14.     Logs and firewood



Grooves, Rebates and Tenons
Cutting grooves and rebates is dangerous because:
        The wood may bind and be thrown back by the saw.
        The position of the saw is hidden when cutting and the cut may finish
         unexpectedly, exposing the saw.
Cutting tenons is dangerous because the wood has only limited stability and may easily
be twisted or jammed against the saw.
These operations must only be carried out on a circular saw if Shaw type guards are
fitted, which effectively prevent hands and fingers touching the saw.




Unit 2                                                                                   19
Carpentry & Joinery – Phase 2   Module 4

Self Assessment




Unit 2                                     20
Carpentry & Joinery – Phase 2                                                       Module 4

Index
                                                                                           Use ...................................................................... 17
  C
Circular Saw ............................................................... 9           R
   Safety................................................................... 10
Circular Saws                                                                          Rebates ..................................................................... 19
   Guard Adjustment ............................................... 13                 Riving Knife............................................................. 14
   Guards ................................................................. 11
Clearing Away and Taking Off ................................. 18                        S
Cutting ...................................................................... 15
                                                                                       Safety
                                                                                          Circular Saw ....................................................... 10
  F                                                                                       Cutting ................................................................ 15
Firewood ................................................................... 19           Push-Stick ........................................................... 16
                                                                                          Riving Knife ....................................................... 14
                                                                                          Unguarded Saws ................................................. 10
  G                                                                                    Saw Blades ............................................................... 10
Grooves, Rebates and Tenons ................................... 19
Guard Adjustment ..................................................... 13                T
                                                                                       Taking Off ................................................................ 18
  L                                                                                    Tenons ...................................................................... 19
Logs and Firewood ................................................... 19
                                                                                         U
  P                                                                                    Unguarded Saws ...................................................... 10
                                                                                       Use of Push-Sticks ................................................... 17
Push-Stick ................................................................. 16
Push-Sticks




Unit 2                                                                                                                                                              21

								
To top