Wt4603 unit3 week4-26-09-2011
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WT4603 Wood Processing Safety & PracticeAutumn Semester 2011Lecture Unit 3 (Week 4)
PLANING MACHINES, HAND ROUTERS & COMPONENT B Lecturer: Mr. Joseph Lyster [email protected] Notes prepared by: Mr. Joseph Lyster Notes available on www.slideshare.net/WT4603
Surface PlanerPlaner Knives Important factors when selecting a planer knife • Suitability for cutter block
• Material being processed
• Finish required
• Volume being machined
• Clamping and setting mechanisms
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Surface Planer
•Planers can have 2,3,4,6……. Cutter knives.
•Most smaller machines such as those found in schools will have 2,3 or 4 knives.
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Surface Planer• Knives can be made from Chrome Vanadium steel
alloy. • This is suitable for machining softwoods and non
abrasive hardwoods. • However with advances in machining technology
better materials have been developed to machine wood and wood composites.
• Chrome Vanadium knives dull quickly on harder more dense material.
• This requires more sharpening, setting up and leads to a lot of time wastage.
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Surface Planer
•High Speed Steel (HSS) is a cobalt steel alloy with a small percentage of Tungsten added.
• It is more suitable for machining all types of wood than the chrome steel compounds.
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Surface Planer• Abrasive stock should be machined using solid or
tipped cutters.• Tungsten Carbide (TC) is the best tool compound
for machining manufactured boards.• For general work HSS cutters are preferred to TC • Cutters can be re-sharpened easily.• A keener edge can be achieved on HSS giving a better finish
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Surface Planer
•The reason for this is that steel compounds are smelted and shaped by rolling and forging while the metal is close to melting point.
•The molecules of the compound flow and align themselves in response to this pressure giving the material maximum strength and edge holding capabilities
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Surface Planer•Tungsten carbide is a sintered compound.
The fine grain powder from which the cutter will eventually will be made is compressed into a mould ( the ‘blank’ un-edged cutter required) under extremely high temperature (1500C) and pressure to form a solid block.
•Tungsten does not flow – it retains a granular structure and will chip rather than deform if abused.
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Surface Planer•Because if its brittle nature TC cutters
require a more obtuse sharpness angle than the HSS cutters (more support for the cutting edge).
•This makes it less satisfactory for cutting softwoods than HSS knives which can be ground to a more acute cutting angle.
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Surface Planer
CutterKnife
TC
KnifeCutter
HSS
Large grinding angle
to support cutting edge
Smaller grinding angle
produces keen edge
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Knife Cutter geometry
• Rake or Cutting angle
• Angle created between the face of the cutting knife and the centre of the cutter block
• Can have a wide range
• Softwoods 27° to 35 °• Hardwoods 15° to 25 °
CuttingAngle
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Knife Cutter Geometry
Bevel or Lip Angle
• Angle formed to give the cutting edge
• Minimum of usually 35°
• Greater for tipped cutters
BevelAngle
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Knife Cutter Geometry
Clearance Angle
• Angle formed between a line tangential to cutting circle and the bevel angle of the knife
• Must be present• Has a bearing on the life
of the cutting edge• Usually 10° to 15°
ClearanceAngle
Cutter CircleDiameter
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Knife Cutter Geometry
Peripheral Cutting Speed
• A constant speed in the range of 35-45 m/s will give best results
• Increase in speed may cause loss of dynamic balance due to vibrations
• Poor finish• Increased noise levels
Cutter Circ leDiameter
CutterRotation
Work Movement Direction
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Pitch distance
• Combination of a rotary cut and a linear feed will leave the surface of the material with a series of arcs on it called Curtate Trochoids
• The pitch and depth of these arcs will determine how smooth the surface finish will be
Work PieceSlower Feed Rate
Work Piece
Pitch
Pitch
tt
t = Cutter arc depth on machined surface
Fast Feed Rate
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Department of Materials Science & TechnologyUniversity of Limerick
Pitch Distance
• 2mm to 3mm for non obvious joinery and painted external work.
• 1mm to 1.5 mm for internal painted work.
• 0.5mm to 1mm for hardwood joinery and furniture.
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Pitch DistanceThe SI unit of time is the second , but the minute is acceptable. Feed rate on wood working machines is expressed in metres per minute. (m/min) The formula for the pitch of the cutter marks is given by:
fp = -------
nR where p = pitch of cutter mark
f = feed rate
n = number of effective cutters
R = revolutions per minute of block
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Pitch DistanceThe unit for “p” will be metres (m) f m/min m minp = ---- = --------- = ----- x ------ = m nR 1/min min 1
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Pitch DistanceProblem 1
Calculate the cutter pitch of a 4 cutter block revolving at 4200 rev/min with a feed speed of 24m/min.
F 24 24p = ------- = ------------ = --------- = 0.0014m = 1.4mm
nR 4 x 4200 16800(Internal painted work)
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Pitch Distance
If a graded surface is specified and the machine has a multi-speed feed gearbox, the same formula is used but “f” is expressed in terms of n ,p, and R.
f p = ------- f = nRp
nR
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Pitch DistanceProblem 2
From a cutter block which rotates at 4200 rev/min and has two cutting knives, a surface finish of a 4mm pitch is required. At what speed should the feed gearbox be set.
f = nRp = 2 x 0.004 x 4200 = 33.6 m/min
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Chip formation
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Riving
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Riving
Cracking occurs below the cut depth
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On the surface planer the in-feed table (A) acts as chip breaker and the downward pressure exerted by the operator also makes it act as the pressure bar.
A
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Chip formation
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Chip formation
• Chip breaking aid and pressure bar prevent riving and splintering
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Circular cutter block
• Reduced noise levels
• Better balance
• Safer clamping mechanism
• Can run head at higher speeds (RPM)
• Can produce better finish
• Easier and quicker maintenance
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Circular cutter block
Clamping bolts are in tension
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Knife clamping mechanism
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Knife clamping mechanism
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Cutter projection
Use of a limiter to achieve limited cutter projection
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Cutter design•Cutters should preferably be designed to be used in
dimensionally similar pairs, formed to the same profile.
•Pairs should be mounted directly opposite one another. The manufacturer should ensure that instructions on balancing the pairs of cutters after grinding are given to the user.
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Cutter projection•The design of cutter blocks should, as far as is
practicable, be such as to prevent excessive cutter projection.
•Where the mounting arrangement permits projection which could subject the cutter to unsafe stresses, the maximum permissible projection for given cutter types should be specified in the user’s instructions.
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Hand-fed machines• For machines designed for hand-fed operations,
where cutters are necessarily exposed, the use of chip limiting cutters should be recommended
• For other hand and semi-mechanical feed operations, cutter blocks should have as little cutter projection as is practicable.
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Surface PlanerCutter and Machine Maintenance Involves: 1. Grinding and setting of knives 2. Roller and pressure bar setting 3. Prevention of resin build up on table and rollers. 4. Attention to:
bearing wear feed complex adjustments rise and fall table
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Surface Planer•The grinding angle of a cutter can
vary between 30 to 35
•This is increased to 40 for hardwoods (cutting edge lasts longer)
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Surface PlanerOverheating •May produce micro cracks in the cutting
edge which can run into gaps when the cutter is used.
•May cause the cutter to bow due to expansion.
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Surface PlanerOverheating can be avoided• By taking light cuts.
• By ensuring that the grind wheel is ‘dressed’ when required to ensure that the face is open and not glazed when grinding the knives.
• By using a ‘soft’ grinding wheel on HSS cutters – the soft structure of the wheel allows its grains to break away as soon as they are blunt revealing sharper ones.
• By wet grinding – this is the grinding of cutters while partially submerged in a mixture of water and soluble oil. The water is a coolant to prevent frictional heat developing and to disperse it should it occur. The oil prevents rust in the cutters and it provides a degree of cutting lubrication.
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Surface PlanerSetting Cutters in Block • Before setting the following points should be checked. • The out feed table and cutter block must be clean and free
from dust resin. • Method of adjusting cutters.
• Area where setting device is used from should be free from resin and damage.
• Straightness of cutters.
• Cutters correctly balanced both in weight and end for end. Department of Manufacturing & Operations Engineering
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Surface PlanerSetting devicesThere are a number of cutter setting devices.This device and procedure will often be supplied with the machine.They can be loosely placed into the following four categories: 1. Bridge device 2. Precision cutter setter device 3. Pin locater device 4. Wooden straight edge device Cutters require accurate setting in the block because if the knives are not revolving
in the same cutting circle a poor finish will be produced.
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Setting Cutter Knives
• Setting of knives will greatly depend on the type of cutter block
• Knife cutter projection• Chip breaker• Knife parallel to table• All knives in the same peripheral cutting circle(Refer to machine manual for setting)
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Setting Planer Knives•When planing wooden material a number of factors
combine to generate the flat surface.•Number of cutting knives in the block•Speed of the revolving block•Feed speed of the material•Knife cutter design•Chip breaking aids•Nature and species of the material
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Knife cutter design & Chip breaking aids
•These factors combine to produce an acceptable surface finish
•Tip of the cutter splits away the chip•The chip is forced away from the stock and up along
the face of the cutter which is exerting a tearing effect on the grain fibre
•As the knife exits the stock the chip is either cut or will “rive” or tear deeply along the grain line and lift as a long heavy splinter
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Knife cutter design & Chip breaking aids
•The cutter projection and the shape of the block face cause the severed chip to bend back causing a crack across its width
•This makes long grain riving less likely(Chip breaker not shown)
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Knife cutter design & Chip breaking aids
• Sharp tooling (a) will aid in the chip bending back and cracking across its width
• Blunt tooling (b) will aid riving
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Chip Formation
Before knife makes its cut
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Chip Formation
Chip to be formed
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Chip Formation
Chip breaker will help prevent riving (a)
a
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Knife cutter design & Chip breaking aids
A. Large cutting angle which gives the knife a lifting action which will cause riving
B. Grinding a face bevel reduces the risk of riving as it changes the cutting angle
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Face bevel on cutter knife (B)
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Surface Planing
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Surface Planing
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Surface Planing
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Surface Planing
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Surface Planing
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Surface Planing
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Surface Planing
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Surface Planing
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Surface Planing
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Surface Planing
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Surface Planing
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Surface Planing
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Surface Planing
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Surface Planing
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Hand RouterConsists of cutter rotating at between 800 to 30,000 RPM being driven by a vertically mounted motor set on a flat based framework
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Hand Router
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Hand Router
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•Cutting grooves•Cutting rebates•Cutting slots and recesses•Cutting beads or mouldings•Cutting dovetails•Cutting dovetailed slots and grooves•Edge trimming•Profiling (jigs/formers)
Hand Router
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• Large powerful routers are heavy and can be difficult to handle for light work.
• Generally in schools the type of work that the router will have to perform will be light to medium work.
• As a rough guide to classifying routers: 400 W to 600W are for light duty 750 W to 1200W are for medium duty 1250 W upwards are for heavy duty
Hand Router: Power
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Collet
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ColletA tapered sleeve that is made in a number of segments that is used to hold the shaft of a cutter or bit.
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• Collet needs to be cleaned regularly
• Must prevent rust
• Must prevent wear
• Can clean with solvents but must spray with WD40 afterwards
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Cutters (Router bits)• Two types of cutter
• High Speed Steel (HSS)
• Tungsten Carbide Tipped (TCT)
• HSS work well on softwood because of their keen edge but will blunt quickly
• TCT cutters perform much better than HSS on hardwoods and MDF
• Cutters should be cleaned regularly with white spirit and fine scraper to remove dirt, resin and debris.
• Cutters should also be inspected for damage prior to operating.
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A router bit is a tool for woodworking giving a quality finish to the material. It cuts wood providing a way to give a clean and even a decorative edge to woodwork.
The following is some basic information about router bits to get you started in your woodworking efforts. Here are the there main parts of a router bit:
1. The shank- the part of the router bit that is inserted into the collet (the sleeve of the router).
2. The cutting edge- this part cuts and removes the wood. They are available in several sizes and shapes.
3. The pilot- the guide for the router in order to make a correct cut. It can be an extension of the shank or a ball bearing attachment.
Cutters (Router bits)
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Cutters (Router bits)
Cutters can have disposable or interchangeable profiles.
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Cutters (Router bits)
Cutter diameter will have a direct effect on the power required form the router motor.
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Cutter selection & feed direction
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Feed direction• If you feed a router into a piece of
material without using a guide fence or bearing guide you will find that the router will pull to one side.
• If you push the router into the material from position (A), the router will pull to your left.
• If you pull the router into the material toward you from position (B), the router will pull to your right.
• This occurs as the cutter will climb on the material in front of the cutting edge.
• This motion must be utilised when using guide fences.
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Feed direction & the fence
To process a straight housing or trench you can use a straight edge guide (A) or the guide fence that is supplied with the router(B).
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Feed direction & the fence• In the photo the fence is securely
clamped in position.
• The router is being fed in the direction (F).
• The router will try to pull to the operators left hand side.
• With the fence clamped on the left of the router, the router will push against it as it is fed into the material.(Green arrows)
• If the fence were on the right hand side (when viewed from the operators position) of the router, it would pull away from the fence and result in the trench being crocked.
F
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Feed direction & the fence• The groove is produced as the router is
moved forward.
• Local extraction will remove the bulk of the dust produced.
• Some may be blown back in the direction of the operator.( )
• A suitable lab coat will protect the operators clothing.
• Appropriate dust mask should be used.
• Feeding the router in the opposite direction will cause any dust to be blown away from the operator.
• This will require the guide fence to be set up on the right hand side of the router and operator.
F
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Guide fence
Guide fence fixed to the router.Can be fixed from either side.
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Using the guide fence
F
P
When feeding the router forward (F) the router will tend to pull to the operators left hand side.
The fence should be set on the right hand side of the router.
When the cutter engages in the material it will pull to the left as indicated by the green arrow (P) and keep the fence tight against the materials edge.
Material should be securely calmped or placed on a non-slip router mat.
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• Profiles can be processed on material using templates.
• Templates can have the required profile as an internal shape or an external profile.
• To process the section marked (A)
• In the photo an internal template can be used to guide the router to produce the profile.
• Feed direction can be established using the right hand rule.
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Fit the template guide to the router base plate.Set cutter plunge depth.Place over template at the starting position (A).Switch on the router and then plunge to depth (B).Feed router in a clockwise direction.
Using the template guide
Router Station 1Carry out the following operations:1. Isolate the router. 2. Select V- groove cutting bit.3. Fit the bit in the router securely.4. Set the depth of the cut to 3mm.5. Machine the profile shown on the drawing
using the guide fence. (Note: Guide fence is set. Do not adjust.)
6. Isolate the router.7. Remove the cutter from the router.
FEEDDIRECTION
ROUTER PULLS TO THE LEFT
FENCE PULLED TOWARDS
WORKPIECE
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Router Station 3Carry out the following operations:
1. Isolate the router.2. Select Ø 6mm cutting bit.3. Fit the bit in the router securely.4. Set the depth of the cut to 5mm.5. Set the depth turret to machine to a depth of
10mm on the second pass.6. Fit the guide fence to the router.7. Set the guide fence to the dimension shown on
the drawing.8. Machine the profile shown on the drawing using
the guide fence.9. Isolate the router.10. Remove the guide fence and Ø 6mm cutting bit
from the router.
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Router Station 4Carry out the following operations:
1. Isolate the router.2. Select Ø 12mm cutting bit cutting bit.3. Fit the bit in the router securely.4. Fix the template guide to the base of the
router.5. Set material in the template.6. Set the depth of the cut to 5mm.7. Set the depth turret to machine to a depth of
10mm on the second pass.8. Machine the profiles of the template using the
template guide.9. Isolate the router.10. Remove the template guide and Ø 12mm
cutting bit from the router.
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WEEK 4: LABSComponent B• You will be provided with two pieces of un-sawn material, both measuring 1020 x 145 x 25.• You will label both pieces B1 and B2, respectively.
B1
B2
Table Top
Back/Side Rails & Drawer Front
1020
145
1020
145
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WEEK 4: LABSComponent B Cutting List
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B1 = Table Top
• B1 must be planed all round (P.A.R) to 1020 x 140 x 22
• The process for B1 will involve the following:• Surface plane/thickness to 140 x 22• Rip B1 @ 67mm (x2)• Thickness to 65mm (x2)• Cross cut to 500mm (x4)
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B2 = Back and Side Rails
• B2 must be planed all round (P.A.R) to 1020 x 140 x 20
• The process for B2 will involve the following:• Surface plane/thickness to 140 x 20• Rip B2 @ 132mm (x1)• Thickness to 130mm (x1)• Cross cut 1 = Side Rails @ 158mm (x2)• Cross cut 2 = Drawer Front @ 272mm (x1)• Cross cut 3 = Back Rail @ 312mm (x1)
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Processing Sequence:1. Surface plane face side/face edge for B1 & B22. Thickness 1 = B1 Table Top to 140 x 223. Thickness 2 = B2 Side/Back rails/Drawer Front to 140 x 204. Rip 1 = B1 Table Top @ 67mm (x2)5. Thickness 3 = B1 Table Top to 65mm (x2)6. Rip 2 = B2 Side/Back rails/Drawer Front @ 132mm (x1)7. Thickness 4 = B2 Side/Back rails/Drawer Front to 130mm (x1)8. Cross cut 1 = B1 Table Top @ 500mm (x4)9. Cross cut 2 = B2 Side Rails @ 158mm (x2)10. Cross cut 3 = B2 Drawer Front @ 272mm (x1)11. Cross cut 4 = B2 Back Rail @ 312mm (x1)
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