Accuracy / Alignment struggles with my PM66

[Brad Ridgway]

Ok, maybe i'm an idiot, but since i upgraded my GI contractor to a used (1999) PM66, i feel i'm struggling with accuracy...


1) The top is definitely not flat. If i throw a straightedge front to back i can see nearly 1/16" of light on both ends. I also have problems with the left most extension wing in particular where no matter what i can't get it perfectly in sync with the top.


2) i have used my TS Aligner JR to try to get everything set as tight as possible (including the back of the fence being ~.003) out further from the miter slot than the front. Yet even when ripping, i am getting horrible results.. the width of the board is inconsistent throughout the cut (and this is using board buddies to pull it tight against the fence). The out of flat top shouldn't cause what i'm seeing here - and though the fence isn't perfectly flat, i don't think it could cause what i see here either.



I'm not sure where to start... don't get me wrong, i know it's a good machine or wouldn't have upgraded, but in a couple of hours i was able to tweak the general to perfection and just can't seem to get there with the PM.


Any tips? Do i find someone to grind the top for starters? Shipping would be a nightmare so is there a certain type of shop i could look for locally (central florida)


thx in advance...
-brad

[Jeff Willard]

1/16"? In terms of a table saw top, that's a canyon, or a cliff, as the case may be. Light can be deceptive. Can you check it with a known straight edge and feeler gauge?

I align the fence relative to the blade, not the slot.

[Brad Ridgway]

Wow you're right light is deceptive and i feel stupid for exagerating. I really looked that big at first glance :) I'm attaching a summary of my findings... This is looking down from back of the saw and the line indicate the direction straightedge was running and where i had significant? gaps.... In that orientation, both far edges of the outer wings are dead flat... But its everywhere else i've got valleys....

I think front to back slope at the infeed/outfeed end of the top would generally be ok for through cutting (dadoes might be impacted), but its the diagonal and horizontas ones that really concern me.

just to the right of the right hand miter(sorry that's looking from back again), there's so little contact for the straight edge, i can spin the thing with almost no effort / friction...

The left most wing (from back) definitely needs to be raises it is .005 lower than the main table all around,

The right wing seem to "warp" differently than the table. I had attempted to reallign this wing previously, but because of the nearly .01 on the back, i either get the middle of the wing higher than the middle of the table, etc... Maybe some shims could help some of the horizontal gaps on the right side (green lines)


Not sure what to do about warp on that wing nor the biggest valley which is the .012 on the main table when taken diagonally... This seems significant enough to impact cross cutting, etc. Or am i being over precise?


FYI - I also checked my fence and overall, i'm within .002 across the length which i think should be ok there? So i ma need to do some more rip tests to see if i can reproduce that issue...


thx
-brad

[Brad Ridgway]

FYI - the throatplate was out for all of this, so this is just the iron... that .005 was the gap right to the left of the slot...

[Jeff Willard]

I could be all wrong here, but I don't think those variances are going to make a difference. I just checked the inspection sheet for my 66 (bought new-2001) and Powermatic allows .010" diagonally. I don't see another two thou making that much of a difference. I think the bigger issue would be to get the wings aligned to the top. The way it was described, that may take some work, but you should be able to achieve it. You stated that the fence face was dead straight (I consider .002" dead straight). If the quality of cut is unacceptable I would look in these areas:

1) First, is it a decent blade in good condition?

2) Check arbor face runout-PM quotes .001" max for a new saw. Also check the condition of the arbor and and blade collar, a burr or foreign object could have an adverse effect.

3) Check alignment of miter slot to blade-PM allows .01" and mine was shipped at half that. That still wasn't good enough. In about ten minutes I was able to tweak that to less than .002".

4) After all that, align the fence to the saw blade. The measurement at the back of the blade should be identical to, or just slightly (1/64") greater than the measurement at the front. This will not only affect the quality of the cut, but is a safety consideration also.

Hope this helps you out.