Table saw blade runout and miter slot parallelism.

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Forum topic by lateralus819 posted 09-21-2015 01:38 AM 693 views 0 times favorited 8 replies Add to Favorites Watch
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2236 posts in 1308 days

09-21-2015 01:38 AM

So I spent a good 2 hours trying out my new Igaging dial indicator I got for xmas 2 years ago.

I tried to get the slot as close as I could. i fiddled for a long time and settled on about .003/.004 for the miter slot. It seems I could do better but I couldn’t get it any more. Would I need to mess with the trunion too?

I also noticed both blades I own seem to be out of flat. I checked the arbor and it was reading flat and true with no measurable wobble.

But both blades seemed to be out a bit.

Lastly, what is acceptable for alignment and runout? I’m goin bonkers!

8 replies so far

View David Taylor's profile

David Taylor

326 posts in 505 days

#1 posted 09-21-2015 02:50 AM

I spent ten years in quality, measuring parts to ensure that they were in tolerance to print. Most of those tolerances were in the .005/.010” range. If you’re within .003, you’re fine. As far as the blades being “out a bit”, what is a bit? And is this over ten inches diameter? Again, if your “bit” is about the same amount out as the .003” your miter slot is, you’re in terrific shape.

It’s nice to be able to see and measure these kinds of increments, but remember that to build anything metal to .000” tolerance is hugely, prohibitively expensive and isn’t really done for anything. even measuring equipment has tolerances built in, though they are usually an order of magnitude tighter. The iGaging Digi Align has a repeatability: 0.0005” and an accuracy: 0.001”

Also keep in mind that wood moves, and it could move much, much more than the tolerances you are seeing. If your 1/8” thick blade is out of flat .003”, this means your kerf might be .131” instead of .125”. This is less than half of 1/64” difference. A 24” wide yellow pine panel will change in width .189” (nearly 3/16”) over 3 percent change in moisture content. Your .003” will be eaten up long before the moisture content changes even one percent.

-- Learn Relentlessly

View TheFridge's profile


5672 posts in 904 days

#2 posted 09-21-2015 03:07 AM

I try to keep it under .005.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View realcowtown_eric's profile


551 posts in 1355 days

#3 posted 09-21-2015 03:36 AM

Dryfid got it right. And a mere spec of dust on the arbor plate could account for that discrepancy on a 10” saw blade..

But I ain’t quite uip to date on modern mfg techniques for saw blades, but in the olden days, many saw blades were somewhat dished, as when they came up to speed, the centripital force expanded th eouter edge to make them run true. The proof is in the cut. that’s what you want to measure with your vernier calipers.

If it’s 5.00 at the start of the cut and 5.00 at the end of the cut, and the piece don’t bind yer in business. The cut is what matters. Some TS afficiandos also tap their fence so that it opens up by a few thou on the back to prevent binding (typically on contractor saws ). Frig, some of the software packages require you enter into the equations glue-line thickness.

-- Real_cowtown_eric

View lateralus819's profile


2236 posts in 1308 days

#4 posted 09-21-2015 10:21 AM

Great to hear. I have the miter slot down to about .003 or so. The blade itself was about the same. So i guess I’m in good shape.

I had it dialed in before, about the same I was just unsure what was reasonable. Thanks.

View toolie's profile


2009 posts in 2046 days

#5 posted 09-21-2015 01:50 PM

The blade needs to be aligned to the miter slot by adjusting the reunion. The fence needs to be aligned to the same miter slot to which the blade was aligned. The fence should, ordinarily, not be aligned to the blade. At least that’s what all,the expert comments on the web say.

-- there's a solution to every just have to be willing to find it.

View rwe2156's profile


2111 posts in 899 days

#6 posted 09-21-2015 04:08 PM

I would start by getting rid of those blades and getting a good one.
Are you sure its the blade and not the arbor?

Measure distance from slot to the same tooth. This applies to both miter slot and fence.
Keep far fence measurement a few thou wider to help with tear out and binding.

Don’t stress out its ww’ing. Just get it close and go to work.

-- Everything is a prototype thats why its one of a kind!!

View Daruc's profile


459 posts in 551 days

#7 posted 09-21-2015 06:22 PM

25 years, I’ve never even measured mine.. (I’m just an old wood butcher though.)

-- -

View lateralus819's profile


2236 posts in 1308 days

#8 posted 09-21-2015 07:51 PM

The only reason I checked it from the last time I did it was my sled wasn’t coming out true. Its fine as it is now! Thanks for teh help all.

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