Hi Jack
The OEM side guide roller clearance?setting is zero to 1thou over the blade thickness (which is very closely controlled to 25thou in all good blades) so 25-26 thou between the rollers?
The blade cuts in the direction its back (the bit behind the teeth) is pointing, so any change in the angle of the blade back affects vertical squareness of cut.?
When you twist the blade, the blade back slants across the gap between the 2 rollers and the slant changes appreciably with any change in the gap and therefore the blade squareness to the vice table changes too, and along with it the vertical cut squareness.
The blade does actually touch both bearings in each guide, it touches the roller inside the loop of the blade on its edge closest to the teeth of the blade, and the outside roller touches near the back edge of the blade (that's how it twists the blade).
Old timers used to set the side guide rollers about 7thou?+ blade thickness apart to prolong the rollers life.?Even set at the OEM 0-1thou clearance, the rollers are not loaded anywhere near their load limit, but when swarf passes through the gap between the roller and the blade, it shock loads the bearings. At 1 thou blade to roller clearance the bearings are destroyed fairly quickly, while at 7 thou it didn't do much damage and the bearings lasted a lot longer.??
Fact is this was only really?a problem if you used liquid cutting lube, which makes the swarf stick to the side of the blade. Steel swarf cut dry doesn't?normally stick to the blade but occasionally a lump goes through which you hear as a bang.?Alumnium swarf is soft enough to squish but builds up quickly on the blade and rollers, robbing clearance until the rollers really do load up and fail.
If top and bottom guides are not both the same then the horizontal cut blade direction also changes, and bang goes your horizontal cut squareness).??
The blade is better supported with closer guide roller settings?and won't wander as much,if you care about squareness, then? use the OEM setting.? If squareness of cut is not that important to you, then more clearance will make the bearings last longer.??
Anyway take the side guide roller clearance as a 'setting' (always do it the same, whatever you do), don't think of it as an 'adjustment'.
You'll learn a lot more from John Piitkins early?doc? 'Blade Tracking and Adjustment for 4x6 Metal Cutting Bandsaws'.? It's not all correct but it's waaay better than OEM manuals. You can find it in the Files section (from the menu?on LHS of the 4x6 Bandsaw site home page) about 2/3 of the way down the first page.?
Confusingly, in the list it's called 'Basic Blade Adjustment and Tracking -? rev-1.pdf' and it looks like the author is Walter Townsend (Walter transferred all the files from our old Yahoo site to??- Thank you Walter! Most of those under his name were written by other people)
Rgds - jv
