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How to Pick the Right Woodworking Saw Blades
If you've been to a woodworking store or looked through a woodworking catalog lately (and if you haven't what's wrong with you) you've probably seen dozens of different woodworking saw blades for sale.
Choosing the right woodworking saw blade, whether it's for your table saw, radial arm saw, or miter saw, is made much easier if you know the facts and terminology behind the different saw blades on the market.
Saw blades are designed to do many tasks in several different types of materials. These can include: crosscutting and ripping lumber, cutting veneered plywood, cutting laminates and plastics, cutting melamine, and non-ferrous metals. The more specialized a blade is the better job it will do for that particular task. Because manufacturers realized that it was expensive to own a different blade to do each of these tasks (not to mention time consuming to change) they developed all purpose blades and combination blades that are "good" at ripping and crosscutting lumber.
Crosscutting: Where you are cutting across the grain (at a right angle) of a board.
Ripping: Where you cut along with the grain of the wood (down the length).
Some of the major design differences of saw blades are: Hook and side relief angles, tooth configuration, number of teeth, and gullet size. Using these in designs in different combinations will determine how the blade will perform in different materials.
Hook and side relief angles: These two angles play a critical part in how the blade will perform. A hook angle of 20 degrees will cut faster but produce a rougher cut. A high hook angle makes the blade act as if it has fewer teeth. It will cut faster and require less power. A lower hook angle of 5 degrees will produce a cleaner cut, but will slow the feed rate considerably because the blade is now acting as if it has more teeth. The side relief angle will affect the quality of the cut due to the amount of heat that is produced. The more parallel to the plate the tooth is, the more it will simply scrape through the wood. This action will cause the temperature of the blade to increase. This will result in resin in wood and adhesives in man-made materials to gum up the teeth with pitch. Manufacturers get around this by angling the teeth back on the sides so not all the tooth is touching the material as it goes through.
Does your blade really need sharpening? If your blade is cutting like it's dull, check first to see if the blade has pitch build-up around the teeth. This is easy to remove and a lot cheaper than paying to have a saw blade re-sharpened. A study several years ago at Pittsburg State University in Pittsburg, KA showed where four carbide-tipped blades each cut between 4,000 and 6,000 linear feet of 3/4" thick plywood before they started to show signs of dulling. That's a whole lot of wood for the average hobbyist to go through. Keeping your blade clean could keep you from having to sharpen your saw blades for a couple of years or more. For more information on cleaning saw blades, click here.
Tooth Configuration: The angle at which each tooth is ground makes a huge difference in how the saw blade will cut. Here are the most common grinds you'll find and what each is best at: Flat or rip grind teeth are parallel to the plate. If they have a high hook angle then they're best at ripping wood. With a low or negative hook angle the blade is best at cutting non-ferrous metals. Alternate top bevel (ATB) blades usually angle every other tooth. These angles are ideal for slicing through wood as you do in crosscutting. This grind also does a good job with ripping operations, just at a slower rate than a rip blade. Alternate top bevel and raker (ABT&R) blades add a flat top raker tooth between the sets of beveled teeth. This allows for faster ripping but still crosscuts well. Another grind called a triple-chip grind is designed for cutting hard wood, plastics, and plastic laminated wood such as melamine. The triple-chip tooth is smaller than the other teeth and gouges out the initial material which is then followed by raker teeth which clean up the edges.
Number of teeth: It's natural to think that the more teeth on a blade the better the cut will be, but that's just not true. Actually, the least number of teeth needs to be used to get the job done. A rule of thumb is that there should be at least two teeth but not more than four teeth in the material you're cutting at any given time. Now, with that being said, if you want a smoother cut lower the blade to get more teeth in the material, and raise the blade if a smooth cut isn't required to help prolong the life of your blade. Rip blades usually have around 10 to 40 teeth. It doesn't even make a whole lot of sense to use a rip blade with 40 teeth if you're going to turn around and joint the edge. Crosscut blades generally have between 40 to 60 teeth and combination blades are somewhere in-between at 40 to 50 teeth. (These numbers are based on 10 inch blades)
Gullet size: The gullet size effects how quickly the blade can remove chips from the cut. A deeper gullet is needed for ripping because more material is being removed. If all the gullets are cut deep, this will cause more wind drag which will make the blade much noisier. Manufacturers get around this somewhat by making only a few of the gullets deep to clean out chips. In cross cutting, the gullets don't need to be as deep due to the fact that the blade isn't cutting as much material.
Armed with this information, you should be able to make wiser choices when deciding between which saw blades you need.
(c) Woodworkers Resource 2007