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Table saw alignment problem

LoveEluRouters's picture

I have a Powermatic A64 contractors table saw. When the blade is in the vertical position, the blade aligns very well with the miter slot (about 0.0015 from front to back). My problem is when


I tilt the blade to 45 degrees, the back end of the blade is much farther than the front from the miter slot (about 1/8th inch), so much so in fact that the blade touches the factory insert.


Can anyone offer any reason/solution to this problem? I have adjusted the trunions to the best of my ability and like I said, the tolerences are good when the blade is vertical.I have run out of ideas.


Thanks.

forestgirl's picture

(post #81040, reply #1 of 10)

I believe there are two possible causes for this misalignment at 45 degrees.  (1) the carriage assembly is not parallel or (2) as you tilt the blade to 45 degrees, the motor is placing a different kind of weight stress on the carriage assembly and pulling it out of alignment. 


From what I've read, the 2nd scenario is very common with contractor's saws due to their design with the motor hanging off the bars that go between the front and rear trunions. 


The 1st scenario is what I encountered with my used Jet contractor's saw, because it had been dropped most likely and threw everything out of whack.  However, the because of the severity of the misalignment, it showed up at both 90 and 45 degrees.  I had to get a service tech to fix it, so would hope that isn't the problem your saw has.



forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)


Edited 2/3/2003 3:30:56 PM ET by forestgirl

forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

fredsmart48's picture

(post #81040, reply #2 of 10)

A while back when I had nothing going on. I was checking out grizzly web site and down loaded a manual and was reading how to adjust the saw. The mention you would need to shim under the trunnion on the 45° to get it true to miter slots if.


Your problem sound like you need to get a manual from PM that will explain in detail how to shim under the trunnion. I think the best bet is to take it to a repair center if you don't think you can do the work your self.

DJK's picture

(post #81040, reply #3 of 10)

This is common to contractor and cabinet saws. Most only align their saw with the blade full up and at 90 degrees and wonder why it burns and binds on bevel cuts. Shims placed between either the front or back, not both, trunion mountings and table will fix the problem. I have corrected this problem on Unisaws and PM 66. Yes even the allmighty ( to some ) PM 66. One should also check blade alignment with the blade LESS than fully raised. I had a PM 66 with an egg shaped arbor pivit shaft that made the blade raise in an arch. Powermatic said I was nuts untill they inspected the part. When I did office buildouts, I puchased a Jet contractor saw for job site work that had an alignment problem. The trunion mounts on the table bottom were mis-ground and caused the blade to rise at a 2 degree angle. About 10 years ago American Woodworker had a piece on aligning your saw at a 45 degree angle, don't recall which issue, I'll try to find it. I have a piece of tool steel 1/4" thick, 2.5" wide, 16" long squared on all 6 sides with a 5/8" hole reemed 2" from the end. I mount this on the arbor and use it to align everything. Can be used for many other alignments as well. A straight, flat piece of lumber can also be used.

LoveEluRouters's picture

(post #81040, reply #4 of 10)

Thanks for your help. My problem didn't used to be a problem. I aligned the trunions to better align the blade w/the miter slot. I am not happy with myself as I didn't need to do this because previously I just aligned the blade with the fence and adjusted the fence. I rarely use the miter gauge as I have a Delta sliding table and use cross-cut sleds. But what's done is done.


If you could elaborate upon how to shim the trunion I would appreciate it. Also, did you dislike the PM66? I ask because in a few years I plan to upgrade and that was my prime candidate. I was also looking a the Laguna and Inca, but that is a bit more $$$$. I may be well served saving the $$$ and buying a Delta or Jet.


Thanks.


Vince

DJK's picture

(post #81040, reply #6 of 10)

Attached is the AWW piece on saw alignment. Scanned it at a low dpi, if it can't be read let me know. I use the same method but I clamp a digital dial indicator to a miter gauge instead of the brass blocks and dial caliper. If the indicator is attached to a miter gauge push the miter gauge to one side when measuring to remove all the play. When finished then run it agenst the fence to set it to the slot. After setting the fence in line with the slot, I clamp the dial indicator to my sliding table fence and run it along the fence to square the sliding table to the miter slot. This aligns the 50" stroke of the slider. Then square the slider fence to the miter slot. For shims I use whatever metal is handy.

Dave Koury

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jgaiennie's picture

(post #81040, reply #7 of 10)

At the risk of alienating the pirates among us, aren't there copyright laws against this sort of posting.

DJK's picture

(post #81040, reply #8 of 10)

Was wondering how long it would take for someone to ask. NO mention in the masthead on page 2 or anywhere else about reprinting.

Dave Koury

alias's picture

(post #81040, reply #5 of 10)

d- just bought the unisaw w/beismeyer fence and plan to assemble it this weekend . was wondering what you used to shim the trunnion on the 45º. any other pointers would be much appreciated. thankyou much..... bear

Dennis02's picture

(post #81040, reply #9 of 10)

I don't have the original message in front of me but from memory I think it refered to a 'contractor's' saw rather than a cabinet saw. (Unisaw). If indeed that's the case, I wouldn't be too eager to fuss with the trunnion alignment - it's a different kind of animal and requires a different approach. The trunnion is mounted to the cabinet in such a way to avoid the sag problem on 45deg tilts.

I'm not the expert here - just what I've read in following table saw alignment discussions.

As a side note - I would be interested in hearing how well the wings align with the table when you go to attach them. My table was warped enough to require some effort to get the wings aligned flush with the table top.


...........

Dennis in Bellevue WA

woodnut@anatechsys.com

........... From Beautiful Skagit Co. Wa. Dennis
DJK's picture

(post #81040, reply #10 of 10)

This type of fix is easier to do on a cabinet than cont. saw. On a cabinet saw the shims are placed between the cabinet and the cast iron top. A horseshoe shaped shim is placed around the bolt, between the cabinet and top, that holds the top to the base. On a cont. saw the shim is placed between the top and the trunnion bracket. Much more difficult to reach if it's in the front. I have performed this fix on over a dozen Unisaws and PM66. ALL the Unisaws needed shims in the front. The PM66s needed them in the back.

On a cont. saw, it's a good move to replace the trunnion mounting bolts to a grade 8. They can be tightened more with less bolt stretch.

With this fix, one is not touching the trunnion, just the parrilelism of the top to the trunnion.

Dave Koury