TS Alignment Problem

[Art Davis]

After coming to the conclusion that I had an alignment problem when I made a boo-boo on a recent project, I spent the afternoon checking my table saw alignment. I attached my dial micrometer gauge to my Incra 3000, put the gauge in the left-hand miter slot, and checked the fence alignment. (Biesemeyer fence) I discovered something I felt was curious: When I zeroed the gauge on the operator end of the fence and checked the displacement along the fence, it was about 3 thousandths away from the miter slot at the far end----but was about 20 thousands away from the slot in the middle! Wow! Thought my Biesemeyer was crooked.

Then I moved the fence and the gauge over to the right-hand miter slot, and it was virtually dead on! (About 3 thousandths variation, with the back of the fence to the right---that is away from the slot and blade.) So--is this typical? Is it my miter slot that has the problem? What do I do.

The saw is a Delta contractors, by the way.

Any words of advice would be welcome. (Telling me to toss the darned thing would find a sympathetic ear, but what do I do in the interrim?)

Thanks.

Art

[Jim Becker]

Given it's dead on with one miter slot and "not" with the other...I'd suspect the miter slot being machined out of "straight". While it's possible that the deviation in the fence face might follow the miter slot that it checks correctly with, it's highly unlikely as compared to the other miter slot being funky. Do be sure that any "slop" is adjusted out of the miter gauge if you haven't done that already.

And if the saw isn't new, you're probably just going to have to avoid the one miter slot for anything "critical".

[Eddie Darby]

Try putting a piece of smooth wood ( I use UHMW plastic that I have kicking around which just happens to fit perfectly ) into the mitre slot that is off, and measure from the fence to this piece of wood sticking up from the slot.

Find out if it is progressive, or if it is a sudden change. Where is it, how much. Also check the total width of the mitre slot at various locations.

The better picture you have by mapping it out to find out what is going on, the better you will be able to see if it can be corrected.

[Eric Haycraft]

The first thing that came to my mind was that the front rail on the biese might not be perfectly straight. Any variation or warp in that rail will be magnified 3-4 times at the back of the fence. This could happen from pretty much anything from shipping damage to not having the wings on the table saw lined up properly and therefore the front rail gets pulled/distorted. I would get the best straight edge you have and check that it is straight. If not that, Eddie's advice seems like another highly likely problem. If both of those check out figure out a way to check how parallel the slots are. If you have a friend with large calipers, that would work, but you can probably rig something up to span part of the distance if you only have access to a smaller caliper.

[Wade Lippman]

If I understand you correctly, you are saying one miter slot is bowed; being .020" closer to the fence in the middle than at the ends? But the other miter slot is true?

That seems unlikely; you are probably measuring it incorrectly.
I can't see it has anything to do with the front rail; that would make it crooked rather than bowed.
But if it is correct (and I suppose it is not impossible), I figure that .020" over 13" is less than a tenth of a degree. While any error is undesirable, it isn't all that major.

[Lee Schierer]

I suspect your measuring setup has a flaw, most likely suspect would be play between the miter slot and the Incra guide bar. If the slot were bowed .020 then I would guess it would be difficult to get the miter gage bar to slide through the slot. If both the bar and the slot were bowed the same amount it would work okay, but then the bar wouldn't go in the other slot.

If you zero out the dial indicator at any point and wiggle the miter gage left and right what sort of variations do you see in your reading? If the gague bar fits tightly in the slot you should see .005" or less. If you see more then you need to tighten up the fit in the slot. I've done this on my miter gauge with some UHMW tape stuck to one side of the miter gauge bar. It filled the gap and makes the miter bar slide smoothly.

Since your Biesmeyer is two sided, flip your set up over and measure the run out on the other side and see if you get the same results.

[Brian Dormer]

I'm with Lee on this one - an error that large sounds alot like pilot error (been there, done that). Try putting a straightedge on the slot to see if it's bowed or not. .020 you should be able to feel the bow, if not see it. Also check if the width of the slot varies along the length.

I'm thinking maybe your measuring jig was slopping side-to-side in the miter slot.