Sliding Table Saw Tolerances

How perfect a cut should you expect? Pros share thoughts. September 20, 2005

I am a one man shop who just bought a 9 year old Altendorf c-45. The first time I laid a piece of 8 foot cherry on the slider and ripped a straight edge, it was dead straight. What I have noticed since is that with using the front shoe to hold the board, with my hands applying pressure on the other end, I many times get a very slight - maybe 1/64th gap when I put two straight lined boards edge to edge. Is this normal? Should I expect total perfection, or should I try clamping instead of holding it with my hands?

Should I just plan for a trip to the jointer after straight lining, or should I expect perfect straightness? I have achieved a number of times this way, so I suspect it's my hands. Anyone’s thoughts and experiences would be greatly appreciated.

Forum Responses
(Cabinetmaking Forum)
From contributor B:
What you describe sounds normal to me. Any slight movement in your hand or at the boot results in a not-perfectly-straight edge. Using the clamp does help. Also, any time you remove material from a piece of solid wood (and, for that matter, any wood-based product) you are altering how the stresses in the wood are distributed. It could easily be that an 8' length of cherry is moving some as you cut it, relieving some of the internal stresses, and the result is a less than true cut. The less material you remove, the less likely the wood is liable to move.

From contributor M:
Just pay attention to what you are doing. If you move your hand during the rip, it will affect the outcome. Try and keep part of your hand on the carriage and the other part on the material. As Contributor B said, you will have internal stresses that affect the straightness of your cut. You will have this in sheet goods too.

In many cases, you machine will be more accurate than the wood. As for running it over the jointer, it depends on what you are going to do with it. If you are gluing up edges, then you will want your edges as straight as possible. Otherwise, I would say that .016 over 8' is pretty good.

From contributor A:

I’m not sure about the Altendorf edging shoe, but what I did with mine was to grind the edge that the board hooks onto to a knife edge so it gripped better and never slid at that end. You should be able to get glue line rips.

From contributor P:
You'll find that all material moves a little as the inherent stresses adjust after cutting, especially in damp or humid weather. I find that I need to rough-rip my ply sheets, wait a few hours if possible, then re-edge and final rip to width. With solid wood, straight-line to within 1/2" or so of final width, wait a bit, then re-edge and see if the problem goes away.