Saw Blade Guide Pressure

Depending on the saw model, blade guides may not touch the blade, or may apply a constant light pressure to it. October 1, 2010

Question
How tight should the guides be to the blade? If the guides are too close, will that create too much friction with the blade?

Forum Responses
(Sawing and Drying Forum)
From contributor S:
If you have guides that have ball bearings, then they contact the blade. In that case the blade should be deflected past the contact point about 1/8 to 1/4 inch. Your manufacturer may have a requirement for you to follow.

Some saws have ball bearing guides on the top and friction guide bearings on the bottom. In that case the ball bearing guides deflect the blade and the friction ones do not touch.


From Professor Gene Wengert, forum technical advisor:
Generally speaking, guides are to prevent catastrophic blade deviation. They would not touch the blade during "no cutting" time or when cutting wood at a normal speed. A guide touching the blade will have friction and thereby generate heat, which can really be an issue for most blades, shortening life and making inaccurate (wavy) cuts. Attempts have been made to develop frictionless guides... Pretty tough assignment indeed.

From contributor A:
On big mills with 12" wide blades, the guides might not touch the blades very much, but small sawmills using 1 1/2" wide or 1 1/4" blades need some down pressure to keep them cutting properly. I run about 3/16" down pressure on mine. Your mill and the blades you are running might require a different setup.

Here's a portion of the blade setup article at Cook's Saw and Machine website, which talks about down pressure:

"First you need to put your blade on and tension it up. Now make sure that the rollers are off of the blade. Then start on the stationary guide side. Bring that roller down to the blade. Once it touches, push the roller down another 1/4 of an inch. This is called down pressure. If you have everything running right, you might be able to run with just 1/8 inch down pressure.

To begin with, I like the 1/4" because it guarantees that I am able to control the blade. Some people like even as much as 3/8" down pressure."


From Professor Gene Wengert, forum technical advisor:
That is correct, and I should have added, as we get guides that are nearly frictionless, we can use the guide to steer the blade and also tension the blade. Such guides are in constant contact with the blade.
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