Reprinted with permission from MLS Machinery, Inc.
Rip Saws
Rip saws will fall into two sections; one is the straight line rip saw, and the other is the multiple rip saw.
The multiple rip saw which basically operates the same as the straight line Rip Saw with one blade but has multiple blades. We discussed this under Planers that had a multiple rip saw on the tail end of the machine. Rip saws can go up to 72" wide; these machines are used for ripping up complete 4'x8' or 5'x9' panels. The standard multiple rip saw would normally be a six, eight, 10" or 12" machine; some American machines are larger, having an 18"-24" chain and arbor. The arbor is the shaft where the multiple blades will fit. These machines work in the same way as the straight line rip saw, having in most cases, a chain feed at the bottom and the blades invariably coming from the top attached to the arbor. The operator will put spaces between the blades, which will determine the width of cut that he wants to make; for example, if he takes a 12"x12' long plank and puts it through the machine to cut up multiples of say, three inches, the blades will be set with spaces at three inches apart and out will come four, three-inch wide by 12' long pieces.
This again is very similar to what can be done on a re saw but the re saw takes much larger pieces IN HEIGHT and can only make one cut at a time.
A rough rule of thumb when determining the horse power required for a multiple rip saw is to find out how many cuts and required at one time and what will be the widest piece. Calculate that the machine will require 5 HP per inch of thickness; this will determine how many blades the machine can take and what horse power will be needed. Example: if a manufacturer wanted to cut a plank that is two inches thick by 12" wide and he wanted to cut five parts at a time, 5 HP per inch in height and we want to do five cuts; that is 5x5, if we are cutting 2” thick material, multiply this total by 2; therefore the answer would be 5 x 5 = 25 x 2 = 50 - therefore we would require a 50 HP multiple rip saw to do the job. 5 HP is normally used for hardwoods and 4 HP will be used for softwoods. When manufacturers of solid lumber talk about five quarter (5/4) or eight quarter (8/4) lumber, etc., 5/4 would mean 1-1/4" and 8/4 would mean 2”. This is jargon used in the industry.
A straight line rip saw is a rip saw that only has one single blade. A straight line rip saw is normally used in conjunction with a clamp carrier, that is, when a manufacturer wants to glue pieces of wood together to make panels. A straight line rip saw will give a good, clean cut and will allow what is commonly called a glue joint cut. When an operator cuts rough pieces of lumber through a rip saw, the next cut piece can be butted together with the first, glue applied, put into a clamp carrier and when dry will give a perfectly good glue joint for the manufacture of panels. The same again would apply if pressed in a high frequency press. To get a good glue joint on a straight line rip saw, the chain has to be in good condition, that is, the little protruding points on the chain must not be flat. The chain on the machine drives the piece of wood through the saw blade and holds it in place with the aid of pressure rollers from the top of the piece so that the piece does not move while it is being cut. This will determine how good a rip saw is for glue jointing.
In some cases, manufacturers will rip up wide, long lumber planks into single long strips. If these pieces will be going into a secondary operation such as a moulder, a glue line joint or glue joint machine will not be required. In this case a straight line rip saw that does not have a perfect chain, will be good enough and will be far less expensive.
To summarize, straight line rip saws actually have two categories; a straight line rip saw that will give a glue joint cut; and a straight line rip saw that will give a rough cut good enough for going into secondary operations.
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