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Saw Blade Guide Pressure
Question
Forum Responses
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. Would you like to add information to this article? Interested in writing or submitting an article? Have a question about this article? Have you reviewed the related Knowledge Base areas below? 
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