Saws

      Basic descriptions of sliding table saws, miter saws, re-saws, and related saw equipment used in wood shops. November 13, 2008

Reprinted with permission from MLS Machinery, Inc.

Band/Re-Saw - A re saw is basically a very large band saw. A band saw can be found in home hobby shops or at Sears. They basically have a long relatively narrow saw blade that goes over two wheels, one on the top and one on the bottom, and are used sometimes to cut small intricate parts. The band saw that you would see at Sears would normally be a 12" machine, that is, have a 12" diameter wheel. The saw blades in this case would only be about one half an inch wide. These band saws get progressively bigger, to say, a 36" band saw that could be used to cut, as an example, chair parts from plywood or solid wood.

The re saw is just a larger version of the band saw. The re saw will have a motor that is 15 HP and up and has blades that are 3-6" wide with very large teeth, the diameter of the wheel being somewhere between36-54" or larger. Re saws are normally used in the saw mill industry and are used to cut up complete logs into planks. Most re saws need a pit for installation so that the bottom wheel has a place to go otherwise the table surface where the operator stands would be too high from the ground. Most of the wheels are rubber coated so that there is no friction between the blade and the wheel. The blade is constantly moving up and down while traveling around the two, which is continuous. In some cases the blade could be 25-30' long if stretched out. Some of these machines can open up to 24" or 36" in height and might have a self-feeding system which could be a hydraulic self-centering system that will push the piece of wood, be it a small tree, a log or a large trunk through the saw blade. If you started with a 24" diameter log, it could be passed through the blade a number of times to turn it into 2" x 2" or 2" x 4".

Chop saws are high production machines not being very expensive. When solid lumber comes into a factory it could possibly be in random lengths 16' or 20' long; this would have to be cut down to the required size as well as cutting out any knots in the wood. These chop saws, sometimes referred to as an undercut saw, will normally be foot pedal operated with a guard that protects the operator's hands from the blade which can cycle almost 60 times in a minute. The operator will push the piece of wood to a predetermined stop and hit the foot pedal; the saw blade will go up and cut the wood while the guard will come down protecting the blade. The operator then pushes the remaining wood to the next stop. These machines can be left- or right-hand justified, depending on the operator or depending on the material flow within the plant. Longer machines will cut larger widths of material and with more horsepower.

Optimizing and defecting saws are a far more sophisticated version of the chop saw but work in a similar way. These are either fully automatic with CNC controls or have high speed feeding mechanisms. The optimizer as its name implies will optimize lengths of lumber from a random length or material that is fed into the machine. The computer has a list of the most common sizes and will automatically determine the best way to cut and optimize the random piece placed into the machine to get the best yield.

The Defecting Saw will remove defects such as knots etc. from the lumber. On the older or less expensive or these machines the operator would mark the defect with a special chalk, a scanner would read these chalk marks and cut out the defect.

The more expensive machines today use scanners and vision and will find the defect on their own without human intervention or a chalk line and will automatically cut out the defect.

Panel saws horizontal are used to cut up plywood or particle board in full sheets, such as 4'x8', 5'x10', or 5'x12' panels. These saws normally have a pre-scoring blade which pre-scores any laminates such as Formica, vinyl, painted board, melamine, etc. on the bottom of the panel so that the board does not chip on the bottom while being cut. The top side will always be clean when cut on a panel saw seeing that a pressure beam holds the panels in place while being cut. These machines cut multiple panels at the same time. Some of them are manually operated with a manual pusher or manually operated set of stops. Some of them are more automated with an electronically controlled pushing device that pushes the panel to a cutting line where the saw blades are located. Some of them are completely computer controlled and some larger systems are available in an angular form which can cross cut and rip cut using a single operator. These angular systems are basically two machines in one. Panel saws normally cut from the underside of the panels so the main blade and scoring blade travels in unison across the cutting line from one side of the machine to the other while cutting the panels. Once cut, the saws disappear under the table and go back to the starting position while the computer repositions the next batch of boards by moving the pushers. This operation will be repeated until the whole batch of panels are completed.

A number of panel saws have air flotation tables in the front to ease the handling of the cut panels. Air flotation tables work similarly to hovercrafts producing air between the product which have been cut (which is normally quite heavy) and the table itself.

Some panel saws are self loading; these are the more automated computerized machines where a whole bundle of uncut panels are placed on the scissor lift which automatically lifts to a pre-determined height. The computerized pusher travels along and pushes the panel onto the machine. This obviously saves in labour costs.

Angular panel saws are for much larger production and can handle about 1200 sheets per day at an average and as discussed above are two complete panel saws in one; one to do the rip cut, which is the full length of say a 4x8 sheet that is the 8' dimension, while the cross cut will cut the 4' dimension. In the other panel saws described above, the panels will normally be ripped first, as in our example, all the required cuts along the 8' dimension will be cut and once this is done, the operator will manually turn the cut 8' lengths and push them back into the machine again so that the required cuts along the 4' dimension can be cut (cross cut).

When a number of full panels are being cut together, the height of the stack of panels is often referred to as the "Book Height". Some machines can cut 4" in height at one time and some can cut up to 6" at a time. 6" would be equal to eight 3/4" panels at a time.

Radial arm saws - The part to be cut is placed on a table against a fixed fence and the operator pulls the saw blade across the piece of wood using a handle. The saw blade is virtually unprotected and can be quite dangerous. For industrial use, the machines just become larger with bigger tables, bigger blades and more horse power. The blade can be tilted at different angles for different angled cuts. Radial arm saws can sometimes be set up on a frame to have three or four radial arm saws working in unison operated by one foot pedal; often used in the door industry to do multiple cuts on one part.

Hydraulic cross cut saws are similar looking to radial arm saws except they are foot pedal operated to move the blade across the material and have much more power because they are hydraulically controlled. These machines can have a far reach, traveling across the table from 38" to 50" long and can often be found to cut counter tops or very wide parts.

Double mitre saws are saws which can be independently operated on a single beam; therefore, one can be set at 90 and the other at 45, as well as setting them any distance apart from each other. The part is placed on two tables located at each saw and is held in place by air cylinders. The operator hits a foot pedal and the blades come down from the top cutting the piece to a predetermined length. Often the blades are set at 45, which is good for the picture frame manufacturers when making a complete frame.

There are many other types of saws available which are not described under this section, i.e. the Midwest counter top saw with built in router motors.

Sliding table saws look almost like table saws but have a large extension sliding table off the side of the machine that slides an equal distance in front of the blade as it does after the blade. These machines normally cut full sheets which can be 4'x8', 4'x9', etc. A full sheet (only one at a time) is placed on this sliding table. The operator pushes the table (which is on a very easy flowing mechanism) pushing the part against the fence set at the pre-required distance from the blade, passing the panel through the saw blade which is stationery. Note the difference in the horizontal saw where the pieces (plural) stay stationery while the whole saw blade carriage moves and cuts the panels as opposed to the sliding table saw where the panel (singular) actually moves and is moved by the operator through a stationery blade. These machines normally come with a scoring saw attachment as discussed previously.

They also come in four feet, five feet, eight feet and 10' configurations. This means that the table will slide, as an example on the 10' machine, 10' before the fixed blade and scoring attachment until the back of the piece passes the blade. These machines are not very productive only cutting one panel at a time, and are very labour intensive because they can only make one cut at a time before the operator has to move the remaining panel and remove the part that has been cut. They take a great deal of space to allow the table to (as in above example) slide approximately 20' in front of and behind the blade, as well as the additional space taken by the actual saw blades themselves; however, contrary to this, they are very popular and are found in many woodworking shops.

Table saws are always required by different companies to do some kind of cutting or another. The table saw is considered as a standard machine and therefore falls under the category of planers and jointers as discussed previously. These are small machines with a single saw blade, normally 2-5 HP motor and a fence; some do have a scoring attachment.

Toe notching machines are where two saw blades come down at 90 from each other to cut out the notch in the bottom of a kitchen or bathroom cabinet so that you do not stub your toe against the cabinet itself.

There are many other types of saws available which are not described under this section, i.e. the Midwest counter top saw with built in router motors.

Vertical saws are upright saws normally used by companies that have limited space and instead of using the horizontal panel saw as discussed previously, will use these vertical saws which stand upright along the wall and can be 10' or 12' long but only stand approximately 2'-3' away from the wall, therefore using more height and less floor space. A full sheet of 4'x8', or similar, is placed on a platform that is attached to the machine vertically and rests against the back of the machine. The saw blade can either be controlled automatically or manually and is run through the board after the board has been placed at certain pre-determined pop up stops on the machine to give the required size. Vertical panel saws are very popular, with some of them having scoring attachments to pre-score high pressure laminates such as Formica or melamine so that they do not chip on the bottom of the piece. These machines are normally very slow and are not for high volume shops. In most cases they cannot cut more than one or two panels at a time and often require more than one operator, because of the material handling that is required.

Some manufacturers have a scoring attachment, a scoring knife that just cuts through the melamine or high pressure laminate. Some make a machine that has a separate small scoring blade attached to the main blade; others use one common blade which first travels up the machine to pre-score and then goes the full depth into the material to do the final cut.

Copyright MLS MACHINERY INC. 2007 All rights reserved.



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