Glenn Roberts wrote on Sep 14
th, 2020 at 8:26am:
Interesting. Ed, after making the wheels "coplaner" (parallel), and assuming you have squared the table to the blade in the x & y axis (looking down on top of the table). For drift compensation, how do you determine the: blade position on the upper wheel, and the rotational position of the table (meaning counter clockwise or clockwise position as also looking down on the table)? Which comes first - the chicken or the egg?
Only since you asked
Here's how I do it.
1. My fence is aligned parallel to the miter slot just like a table saw and does not get adjusted ever.
2. Back off the guides
3. Mount blade loosely on both wheels
4. I roughly position the blade somewhere in the general vicinity of the upper wheel as a basic starting point.
(where it's positioned
is not critical, the blade is flat, the wheel is crowned, when we adjust for alignment (tilt the wheel) it will find the position it needs to be in.
5. I add some tension to the blade and make sure everything is operating smoothly.
(I don't add full tension because it's easier for the blade to move on the tire with less than full tension)
6. I position the fence and make a rip cut in something at least 1 1/2" thick and at least about 10" long, 2"x4"s work well for this. (Before cutting, make sure the edge that's against the fence is straight)
7. Checking the cut. It's usually easy to tell if the cut is wandering toward the fence or wandering outward. If you can't easily tell, you're probably getting close. The easiest way to tell is to rip a piece, then flip the board over end to end and check the clearance at the blade. The clearance should be exactly the same at the end of the cut as it was in the beginning. If it appears that there's a wider gap (board got skinnier) then the cut is wandering toward the fence (blade too far forward) and visa-versa. There is no need to draw parallel lines down the length of the board unless you reference the cut line
8.This is where the adjustment starts. I turn the tracking adjustment knob in small amounts, usually 1/4 turn increments, sometimes less. Then I move the fence in a bit and cut again, repeating the above procedure as many times as necessary. When the beginning of the cut and the end of the cut have the same clearance, you know the cut is parallel.
This is not something that really needs to be measured. The clearance is usually just touching, not enough to create resistance, just touching.
When I'm satisfied with the alignment, I add full tension to the blade and make another test cut to confirm. After that, I adjust the guides to my desired tolerances.
Done
As you cut thicker stock, in the 5" and above sizes, your cut
may start to wander a small amount. The more teeth in the cut, the more chances for the blade to wander off course You can easily make a small tracking adjustment and dial it in without any fuss.
Also feed pressure and blade tension should be watched as a potential culprit.
Too much pressure and the blade will not cut straight. Blade too loose and blade will not want to cut straight.
I don't worry about where the final position of the blade on the upper wheel, a little toward the front or back is fine. If it's
too far toward either extent, it will still cut straight but the blade will either be tilted forward (grabbing the top of the stock first) or tilted backwards (cutting the bottom edge of the stock first). Neither scenario is desired.
Remember, the upper wheel tilts and has a crown, the position of the blade on the wheel can be deceiving. The blade will always ride at the top of the crown. If the wheel is tilted one way or the other, the top (highest part) of the crown may not be exactly centered as you perceive it.
Attached are photos of my saws blade positions. As you can see in both photos, the teeth are not touching the tire as Reed mentioned, the band
only,(not the teeth and/or gullets) is generally in the center, possibly a small amount forward, not a big deal. I sure they move a small amount during alignment.
If I wanted to
, I could reposition the blade back a small amount and re-align to get it perfectly centered, but there's no point as I stated above.
Each saw cuts without "drift"
As always, this is just my method, if you have a method that provides you with the results you want, I'm not trying to change your mind.