We have a couple traditional upcut saws that we use for defecting. So we want to be able to cut at a particular point on the piece, not to any specific length. The problem is that it's about impossible to do it very precisely because you can't see where you're cutting because the guard is in the way.
I was thinking that if we raised the guard a bit higher than "normal" maybe we could set up a laser line generator but when I took a good look at things it seemed you'd have to raise it way higher than would be prudent, not to mention that there's no easy place to fit a laser.
My current thought is to cut off the top part of the guard and replace it with polycarbonate, and fit a laser into that. My concern is that static will make the sawdust cling to the plastic and prevent you from seeing through it.
that setup looks tricky.Maybe put a reference mark on the fence, maybe 10" from the cutline, then just place a mark on the board 10" from the desired cut and line the marks up. You could have a precut board that's 10" to use as a marking guage, to eliminate the need to measure anything
I wouldn't consider what we need to be "precise", but we do need some fairly repeatable accuracy.
We are defecting material, so +/- 1/2" may take an extra 1/2" (doesn't seem like a huge deal, but if you make 1,000 cuts a day that's over 40LF, or 10,000LF a year), or you may cut 1/2" short of removing the defect, meaning you have to cut it again.
After cutting short enough times, and having to re-cut, I think the guys' tendency is to cut too much, and now we're potentially looking at the 10,000LF per year number. Even on an overall average material cost that could easily be $25k...
Max's suggestion makes sense. Since you can't see the cut location clearly, use a "marking gauge" indexed to the defect and a reference point on the fence that you can see. Should get you within 1/16" easily or less if used with care.
We had the identical saw, concerns, and problem solving scenario. I gave up on the jump saw. Now I have a brand new upcut saw that doesn't make a very good table sitting there collecting dust. To replace it we bought an industrial Saw Stop with a sliding cross cut accessory. We built a few jigs that we clamp to the table that makes the defecting faster and less wasteful. It is astonishing how much difference 1/16" of sawdust makes on yield when you do 1000s of square cuts in a day. To supplement this sliding table saw we still use traditional miter/ chop saws which regularly wear out. I think the Saw Stop option is the safest, too, between all three.
I was cutting a cabinet door job this morning and thought about this post. Here is what I came up with:
Measure kerf to edge of blade guard. Mine is 1.5". Then make a couple of corresponding marks somewhere convenient, like the back fence. I marked up a board to show how I used these reference marks. By putting these lines at the infeed edge of the blade guard, the cut will be in the right spot.
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