Editor’s note: This column was produced before Gene Wengert died in 2025. It is printed here in memoriam.

Q. Why don’t we use thinner saw blades on our gang rip or straight line rip (SLR) saws?

A. This is a great question as the sawdust created when ripping lumber can exceed 8% of the lumber’s volume. There are several reasons why we use a thick sawblade. All are directed at making the blade cut as straight as possible.

Here’s the technical explanation. When we spin a flat disc, the higher the RPMs, the more the outside rim wants to stretch and get larger while the inside sections tend to have little force that wants them to expand. 

If we add heat to the outside spinning circle blade, the heat makes the outer rim want to get even longer.

In some cases, water is put onto the hot rim and teeth, cooling them off and straightening the blade. As can be imagined, considerable amount of water problems can be created with the heavy wet sawdust. 

This cooling actually allows for a thinner blade without affecting quality of the cut (assuming the water on the wood is okay).

Another technique is to use a thicker blade that is harder to deform with heat and rotating speed. This is the simple answer to your question, but there is more.

A lot of work was done to address this issue years ago. One solution was to take the flat plate when it is not spinning and dish it, in other words, make it uniformly curved, so the rim is not lined up with the body of the blade. Now, when the blade wants to get longer, it can do so easily by straightening or flattening the blade. 

Years ago, blades, both circle and band, were created with this slight bend by pounding the center sections with a hammer to dish the blade. This hammering was quite an art, and there are probably less than a dozen people in North America who have the skills anymore. What has replaced hammering is rolling the blade and accomplishing the same dishing effect. The roller itself is a machine that is manually controlled to create the needed amount of dish. Overall, a lot of work has been done to stiffen the blade while making it thinner.

A properly rolled or dished blade will be curved when the blade is stationary. As it reaches its designed RPM, it will straighten. It is amazing to see this and hard to believe, but it is true, with the dish sometimes being an inch or more from the center to the rim.

Another point is that we want to have teeth as sharp as possible to minimize heating. The tooth includes both the top edge of the tooth and the two sides. Often side dressing, sharpening the sides, is not done, which adds greatly to the heat. 

When cutting in the old days, high-speed steel teeth were common with variations in geometry. Then carbide was added as a tooth material because of its hardness and longer running time. Recently other materials have been used as tooth material; my favorite is diamond, which gives an easy cut and has very long sharpness.

Another technique to assure blades cut sharply, especially in a gang circular saw, is, when stationary, to hit each blade with a small hammer and note the blade’s resident frequency. The lower the frequency, the more saw movement when spinning and the poorer the cut. Stress added when dishing can be related to the straightness when spinning. So, each blade can be tested for its own frequency, making sure the stresses are within desirable limits. This is especially true with a gang saw, as one blade that loses its dish, also called losing its stress, can create havoc, even though all the other blades in the machine are just fine.

Sometimes we believe that a little bend or residual stress lengthwise in a piece of wood can be fixed by bending it straight in gluing and then gluing to another straight piece so that overall the two pieces should be straight. Often, they are indeed straight, however, the stress involved in keeping the warped piece straight transfers to the glue line, leaving less glue bond strength available for holding all the pieces together.

So, overall the effort in sawing needs to be to create the flattest, straightest surface possible. That might mean eliminating some warped lumber from the supply if perfection is required. Proper rolling is required, depending on blade diameter rotation speed. Side dressing is important. Diamond tips might be required. Overall, each 1/64 inch improvement or reduction in blade thickness has the potential to save 1.5% in yield. That is easily worth $50 per 1,000 board feed of parts.

One area often overlooked for yield improvement when ripping is to make sure the first and last rip cuts are made in wood waste material. In other words the first and last ripping cuts can use as thick of a blade as desired since they’re making sawdust out of waste wood. 

Achieving this goal has enough benefit that every rip cut should be analyzed and decide if a computerized positioning system is worth it. It doesn’t take much improvement to show that a good vision system easily pays for itself at the ripsaw, including gang and SLR, as well as circle and band saws. Also, the first cut saw can be a little thicker than the other size as it is working in waste wood, so its thickness means straighter cuts.