For any saw to cut properly requires just the right amount of set. Too much and the saw requires too much effort to use, too little and it binds in the cut. In this article we'll investigate what set is, figure out how much is needed, and discuss how to properly apply it.
Saw set is the slightly increased thickness of the blade at the cutting edge. This is necessary because if the blade were a constant thickness throughout, the saw would soon bind in the wood being cut due to the friction bearing against the sides of the saw. To overcome this problem, the blade is made slightly wider at the cutting edge by bending every other tooth outward away from the center of the blade. This bending is accomplish with a saw set, a specialized tool made just for this purpose. The increased thickness of the blade at the cutting edge causes the saw to cut a wider kerf than the saw is thick, allowing the saw to cut quickly and efficiently through the work.
The topic of how much set is required in a saw is one that has many answers. It depends on factors such as the type of blade, the thickness of the blade, and the type of material being cut.
First of all, saw blades are generally found of two types, taper ground and constant thickness. By far the most desirable is a taper ground blade. A blade that is taper ground is thicker along its edge than it is at the back. This is a great help in applying set as the blade already has a certain amount of clearance built in. A blade that is taper ground requires less set than one that is a constant thickness. This causes the overall thickness of the edge to be thinner and results in a thinner kerf. A thinner kerf requires less effort to cut than a thicker one. It is for this reason that saws with taper ground blades are so desirable.
The thickness of the saw blade is also important. Most high quality taper ground blades are about .035 inches thick at the cutting edge. They vary from manufacturer to manufacturer. Blades that are about this thickness seem to strike a good balance in that they are thin enough to produce a narrow kerf, but thick enough not to kink while in use. Blades that are a constant thickness generally fall into two categories, saws that are very old, and saws that are of recent manufacture. Saws tat are very old, that is that date from the early 19th century and before, are usually the same thickness throughout due to the limitations of grinding equipment at that time. Saws produced in the mid 19th century to the late 1960s are usually taper ground. Some lesser quality saws of this vintage can be found with constant thickness blades. Saw blades of very recent manufacture are also usually the same thickness throughout, and should be avoided.
The amount of set required is different for softwoods (or wood that is wet) and dry hardwoods. Dry hardwoods require much less set than do softwoods or woods that have not been dried. For softwoods, this is due to the resinous pockets that are encountered in the cut as well as the gummy nature of the saw dust created during the cut. For woods that are wet, this is due to the gummy nature of the dust as well as the tendency of the wood being cut to warp and twist as it is cut.
The actual amount of set applied to the blade is measured with a micrometer A good method to use is to measure the thickness of the blade just above the teeth to get an idea of how thick the blade is without any set. Unless a saw has just had new teeth cut, it will have at least some set. Let's say we measure the saw in question and the blade is .035 inches thick. A good rule of thumb is to increase the thickness of the blade by 20% for dry hardwoods, and 25-30% for softwoods. So, our .035 blade would need to be increased to .042 inches for use in hardwoods, or up to .046 inches for softwoods and wood that is wet. This is just a guideline, but it is a good place to start until experience with your particular set is gained. After setting a few saws and receiving feedback from the work, you'll define a very narrow range on your set which produces good results time after time without going through the hassle of measuring your blade and doing calculations. It should be noted that blades with constant thickness will often require even more set. Sometimes so much set is required that it takes forever to make a cut due to the extreme amount of material that must be removed. It is for this reason that constant thickness saws are best avoided. Fortunately, 90% of the saws that are encountered are taper ground.
So, we've determined how much set is required, but now how to apply it? There are many, many different types of saw sets that one could use. The simplest type is a saw wrest which is nothing more than a piece of steel with slots cut into the edge. The slots are of various thickness for different thickness blades. Saw wrests are difficult for the novice to use, and tedious for the experienced. It is for this reason that there were so many different types of mechanical saw sets developed. There are basically two major types that are likely to be encountered. Both have two handles, one of which moves and pushes a plunger forward to set the tooth. The difference is in the construction of the anvil. The anvil is the part of the saw set that the tooth is pushed up against. The farther the anvil is away from the tooth, the more set the saw tooth receives. One major type of saw set has a rotating disc for an anvil. The disc is ground so that the edge is gradually relieved more and more. In addition, numbers are stamped around the edge of the disc which are supposed to correspond to the pitch of the teeth being set. if this type of set is to be used, it is my experience that it is best to avoid relying on these numbers and instead set up a baseline by trial and error. The second major type of set has an anvil which consists of a beveled piece of steel which can be slid up and down a track. This type of set usually just has arbitrary graduations instead of actual numbers. This type of set is by far my favorite. The Stanley 42X saw set is of this type and is a very well designed, easy to use tool. Even better, they can be found for $20-40 on the old tool market, often in their original box with instructions.
The conventional wisdom is to set a saw's teeth before it is sharpened. I disagree with this approach for several reasons. If a saw is set before it is sharpened, then part of the set is removed when the teeth are filed. It is very difficult to try to figure out how much the set is decreased in filing as it is dependent on many factors such as how sharp the file is, how hard you bear on the tooth with the file, and how uniform the saw teeth are filed. I prefer to set the saw after it has been sharpened. The saw set, of course, being made of cast iron will dull the teeth unless steps are taken to prevent it. I tape small pieces of veneer on the part of the set that the saw teeth bear on with double stick tape. After setting a few saws, the veneer will start to wear through and is easily replaced. By setting the saws teeth after it has been filed, a very uniform set can be achieved which not only makes the saw cut well, but also makes a very nice finish on the piece being cut. It only takes one or two teeth to be over-set to make the edge of a cut piece of wood ragged and rough.
Actually, setting a saw is a fairly quick and easy task. It doesn't matter where you start, at the heel or the toe of the saw. I like to start at the heel of the saw because these teeth usually aren't used in cutting which make them ideal candidates to use for calibrating your set. It is important where the plunger hits the tooth to provide the best set. In crosscut teeth, line the plunger up so it contacts the tooth exactly where the two fleam angles come together. Hitting the tooth here gives you the best leverage and provides a very uniform set. For rip teeth, let the plunger make contact with the tooth just below the cutting point. It is very important that you not push on the center of the rip tooth as you have very little leverage there and consequently won't move the tooth over very much. What I mean by leverage is that the other side of the tooth is sloped back at a 60 degree angle. The closer you get to the slope, the harder it is to move the tooth out away from the blade. Staying on the other side of the tooth increases the length of the lever and makes it easier to push the tooth. It sounds confusing, but after setting a few teeth, you'll quickly understand what I'm talking about. Adjust your set to a minimal setting. Start at the first tooth under the handle and line up the set plunger on the tooth. Firmly and smoothly grip the handle to set the tooth. It is very important to use the same amount of pressure each and every time you set a tooth. To do otherwise results in teeth that have different amounts of set which will make the saw difficult to use. Skip a tooth and set the next tooth, and so on. After about an inch has been set, flip the saw around and set the teeth you skipped from the other side. When you're done, you'll have a small amount of blade to place your calipers on and take a measurement. Hopefully, you'll be short of the desired thickness. Increase the amount of set by moving the anvil on your saw set. Repeat the procedure on the same teeth and measure again. Continue until you've reached the amount of set calculated. Once your saw set is calibrated, set one entire side of the saw, turn the saw around, and set the teeth on the other side that you skipped. When you are done, sight along the teeth. They should be evenly bent outward, the same on each side.
The ultimate test of any set job is how well the saw cuts. Take some scrap and start a cut. The saw should glide through the wood without jumping around in its kerf. It should not be hard to push, nor should it be "roomy" in the kerf. If either of these conditions exist, increase or decrease the set accordingly. If the saw tracks away from the line, the side of the saw that is furthest from the line has too much set. A simple remedy is to lightly stone the edge of the offending side with a medium India slipstone. Take one swipe with the stone, and try another cut. Usually only one or two passes with the stone will correct the problem. Don't remove too much, however, or you'll have the same problem on the other side until not enough set is left to make the cut.
Once you've determined by trial and error that you have just enough set on that particular saw, make a note of where your saw set is adjusted for future reference. You'll find that you'll move your set very little for all the different saws in your shop.
A properly set saw is essential for trouble free, enjoyable cutting. Once you understand what set is, why it's important and how to apply it, you'll be a long way toward that enjoyment.
Art work from:
Disston Saw Tool and File Manual, 1936.
Biddle Co. Catalog 1910
© 1997 Peter Taran. All rights reserved.