Table saw tolerances

[Don Foley]

When cross cutting on my table saw I am not getting ninety degree cuts.  

For reference I am using the Craftsman version of the Rigid model R4512 saw, and my miter gauge is an Incra 1000HD.

So far I've checked the alignment of the miter gauge to the blade and it is right on at ninety degrees.  Thinking my trunion might not be aligned parallel to the miter slot I checked it and found a .005 or five thousands difference on the same tooth between the front and back of the cut. 

Additionally the amount my cuts are off is greater than .005 every 10 inches.  Also when ripping using the rip fence my cuts are accurate.

My question is how close is close or is it worth trying to align the trunion for this close of a tolerance?  How close is the tolerance on tour saws?

Thanks in advance for your input, Don.

[Don Foley]

I got my own question answered locally.  After conversing with several experts locally I was told not to mess with the trunion.  A difference of .005 is negligible, in fact many saws never get that close of an adjustment.  Popular consensus was don't mess with anything under .010.  

The thought locally was perhaps the square I used to set the miter gauge was off.  That sets today's project, play with the adjustments until I get square cuts.

Don

[John Barr]

You need to align the fence of your miter gauge to the miter slots NOT the blade, See why in this video

https://www.youtube.com/watch?v=NrTeFQ0iQ5k

I have found a way of doing this which is very accurate. I make a small jig 12" by 12", wider than the distance between the slots and the blade with a runner that fits the miter slot without any sideways movement, like you are building a sled. I then move the jig through the blade via the runner and the end result is a cut that is perfectly parallel to the slots. I then reference of that edge with the fences of all my crosscutting devices including the incra miter gauge. I get perfect 90 degree cuts every time.

[Don Foley]

Thank you John.  I reset my miter gauge 90 degrees to the slot (it was barely off) and now am getting good square cuts.

[John Barr]

Well done Don. As for tolerances, I have a story. When I got my saw over 12 months ago I measured the tolerance to be .002 which is brilliant and I should have left it but stupidly I decided to get it to .001. I watched all the videos and I thought this would be easy but after many hours, yes hours I ended up with .008. I couldn't get it better. I ended up paying a technician to get it back to .002. The best he could do was about .006. I was stressed that my brand new expensive saw wasn't as good as it should be. A friend came around that afternoon to help me make something for him, anyway all cuts were perfectly square. All were dead on parallel. All were smooth with no tear out and no visible teeth marks. It was cutting perfectly. My friend said why are you stressed?? This machine is brilliant. Thanks to him I quickly forgot about tolerances and just go on with enjoying my saw. One site I read said that it should be less than .003. I now realize that that's overkill given that wood can expand and contract by more than that. We are not doing any precise engineering work here. If you saw cuts well then forget about tolerances

[Carlos]

thanks for sharing this very interesting video, now I shall go home and try this.

John Barr said:

You need to align the fence of your miter gauge to the miter slots NOT the blade, See why in this video

https://www.youtube.com/watch?v=NrTeFQ0iQ5k

I have found a way of doing this which is very accurate. I make a small jig 12" by 12", wider than the distance between the slots and the blade with a runner that fits the miter slot without any sideways movement, like you are building a sled. I then move the jig through the blade via the runner and the end result is a cut that is perfectly parallel to the slots. I then reference of that edge with the fences of all my crosscutting devices including the incra miter gauge. I get perfect 90 degree cuts every time.

[John Barr]

Don's first post was about accurate cross cuts on a table saw not a miter saw. How do you align the fence of your sled then? My method above only works for miter gauges. For my sleds I use the 5 cut method. Very accurate. If you haven't heard of that just google it. Its a more defining method than the flip over method where you make a cut then flip a piece over and see if there are any gaps. This doubles any error. The 5 cut method actually multiplies the error 4 times.

Charlie Lenz said:

 Most of all my crosscuts are made with a compound miter saw ( CMS ). About the only time a use the table saw miter gauge is when a board is too wide for the CMS to cut, and even then I'm more likely to use a sled then a miter gauge.