Table saw alignment issues

[DavidD]

After a variety of issues, I was checking blade parallelism on my TS (Grizzly G0691 - cabinet saw) and found it was a bit off. I raised the blade to full height and re-aligned to the right miter slot using a dial indicator (~0.001" front to back). After lowering the blade to my cutting height, I re-measured and found that it was out of alignment again (~0.007" front to back). I raised the blade and checked again - dead on.

What's going on???:BangHead::dontknow::BangHead:

I measured at various blade heights to see how the alignment changed with blade height. I had a Freud Heavy Duty Rip blade and measured to the same spot on the blade. Measurement was also 1.25" above the table surface. (Sorry about the format - it's hard to make a table on this forum.:tinysmile_cry_t

blade ht___measurement @ front___measurement @ back
3" (full ht)_zero indicator__________<0.001
2.75"_____+0.006________________+0.013
2.50"_____+0.006________________+0.011
2.25"_____+0.006________________+0.011
2.00"_____+0.006________________+0.010
1.75"_____+0.007________________+0.011
​

To verify that it wasn't due to blade warpage, I repeated the measurements with the same blade with the arbor nut loosened blade rotated ~90 degrees and arbor nut just snugged. I also put on a different blade (Freud Ultimate Plywood and Melamine). I got essentially the same results as above for all attempts. I replaced the original blade and re-measured and again got the same results (have lots of reproducibility).

I also verified that the blade was 90 degrees to the table, but even if it wasn't, it would not explain the alignment issues.

So, I don't know what to do next. Do I just re-align at somewhere a bit below full height and avoid cutting at full blade height (this is a rarity anyhow)? Or is there something that I'm missing?:dontknow:

I'd greatly appreciate any ideas.

Thanks in advance,
David

 

[mark2]

is it possible that the full height limit adjuster is putting just enough pressure on the assembly to cause a slight flex and giving the parallel readings but when backed off to say 2.998" the stress is relieved and blade is out of alignment again?

 

[Live4Brew]

I saw this on my dad's old Craftsman. The trunnion didn't raise the blade in a perfectly straight motion. It essentially 'wobbled' as the blade was raised, changing the angle of the blade slightly - which would cause the same issue you have.

When you quickly raise or lower the blade, can you see any wobble?

 

[RayH]

Hi David,

I know little about power tools, and even less about the statistics of measurement. but as you mention, the problem appears to be at full extension. At this point are you against the stops? If so, it seems that pushing against the stops is shifting the arbor angle. Is the age of the saw such that the trunnion has developed enough wear to cause this? I am not familiar with the Grizzly, but are the trunnion mounting bolts all secure? Are there any other adjustments/attach points that might be worn or loose to allow the arbor shift when it hits the stops?

Unless something becomes obvious, or it is still under warranty, you may have the best answer by just not using full-aginst-the-stops height.:tinysmile_cry_t:

Not a good answer:no:, but the best I can do.:wsmile:

good luck,ccasion1
Ray

 

[ehpoole]

blade ht___measurement @ front___measurement @ back

3" (full ht)_zero indicator__________<0.001
2.75"_____+0.006________________+0.013
2.50"_____+0.006________________+0.011
2.25"_____+0.006________________+0.011
2.00"_____+0.006________________+0.010
1.75"_____+0.007________________+0.011
​

When I look at these numbers, this is what they tell me:

1) From front to back of blade you are registering about 5 mils of error, this is likely due to your miter slots not being perfectly parallel to the blade. If you have cabinet mounted trunions this is a simple fix, just fully loosen 3 corners of the table and partly loosen the 4th corner, then use a mallet to rotate the table in the proper direction about the 4th corner bolt until the miter slots are parallel to the blade (or as close as practically possible -- a few mils of error is fine). If your saw does not have cabinet mounted trunions, then I would probably just live with the 5 mils as it is an acceptable error and non-cabinet mounted trunion saws are much more challenging to adjust (unless you install aftermarket PALS or the like to assist in the alignment).

2) Once you account for miter slot to blade alignment issue, you have a much smaller error to work with. You will notice that, except for the full height numbers (2.75" to 3"), your error is remarkably stable. This should tip you off that the issue is extending the blade to full height, so you should make your measurements at something less than full height. Since we seldom make full height cuts, this should not be a major issue with regard to everyday use. So go ahead and adjust your saw with the blade at 2.5" and be done with it.

HTH

 

[DavidD]

Thanks guys,

After reading the first couple replies, all I could say was DOH! (Homer Simpson Style) :slap:

Sometimes one just needs someone else that hasn't been fretting over a problem to point out the obvious.

I seem to have gotten too caught up in trying to figure out what was happening between 3" and 2.75" when it really doesn't matter. (I do have a tendency to do such things.)

I re-aligned at 2.5" and that will be that. I have certainly gotten lots of practice aligning blade to miter slot lately.:roll: