Table Alignment (Squareness) Done on the Work Bench

[dusty]

This thread is a takeoff from a thread started by dynabase titled "My 520 started singing today".

Fortunately, his 520 has quit singing and his table now aligns properly though the blade still aligns a bit left of center in the cutout.

He has provided me with a trunnion that has two undrilled holes. Shopsmith provided him with a trunnion that has two 1/2" holes (the alleged fix for table alignment issues).

It was my intention to equip one of my tables with two trunnions that are both undrilled just to see how an immovable table aligns to the blade. Unfortunately, I have gotten overzealous in packing and I have squirreled away my undrilled trunnion. Now I have to come up with a different approach to determine whether or not the 3/8" trunnion holes prevent proper table alignment.

My contention is that they DO NOT.

I am going to begin this effort by performing a pseudo table alignment with the table upside down and setting on my work bench. Preliminary testing indicates (to me) that it will work.

Pictures and SU Drawings to follow.

[sehast]

As I indicated in a previous post, I have a trunnion that has just one 3/8" hole on the left outfeed. I have found alignment to be no problem but I have 3 other larger holes for adjustment. I have found that having one a 3/8" is even a benefit in doing the alignment. Only problem is you will not be able to center the blade if your Carrige Stop Ring is not the right size. I had an older 1 3/8 ring but when I did the PowerPro upgrade and changed out the work table to a newer one, my blade would not center. Not sure which of those things caused it but with my old ring the blade was noticeably not centered. After I installed a new 1 7/16" stop ring the the blade centered to within a 1/32". My gut feel is that if all four holes were 3/8" you would still be able to align the blade to the table but there is not much slop there for adjustment so your experiment will be useful.

[dusty]

Problem solved! At least one of them. I located a trunnion with original size holes (3/8"). I can now check for alignment with no holes enlarged in either trunnion.

In the meantime, however, I installed the trunnion I got from dynabus. I installed it with only the left rear bolt installed. This creates a pivot point with virtually not lateral movement.

I then measured from the edge of that trunnion to the edge of the table. It measured 7 5/8". I then moved to the other trunnion and made that same measurement. It was something different so I moved the trunnion until the measurement was 7 5/8". My expectation is that when I install this table on a Mark V and measure squareness to the blade that it will be very close to square and nearly centered in the cutout.

I tightened the three bolts and double checked the measurements. I then installed the fourth bolt. It screwed right in with no difficulty. Because of the way I got to this point, I was not sure that the bolt would align to the hole. These five pictures depict what I have done so far.

Undrilled Trunnion 003.jpg (2.17 MiB) Viewed 7836 times

Undrilled Trunnion 006.jpg (2.16 MiB) Viewed 7836 times

Undrilled Trunnion 007.jpg (1.84 MiB) Viewed 7836 times

Undrilled Trunnion 008.jpg (1.63 MiB) Viewed 7836 times

Undrilled Trunnion 009.jpg (1.99 MiB) Viewed 7836 times

Just as I had hoped.

Later pictures will show just how well it aligned to the blade. It is NOT within my normal target range of .005" and it is not centered but it is close enough to SAFELY used the table saw without further adjustment.

[dusty]

The images that I have do not tell the story accurately because of camera angle and sun glare but I will get others before I change this setup. Here is what I have showing that the right hand face of the blade is 3 3/8" from the near edge of the right hand miter track.

Undrilled Trunnion 018.jpg (1.75 MiB) Viewed 7831 times

Undrilled Trunnion 019.jpg (1.7 MiB) Viewed 7831 times

This basically places the left face of the blade very near center of the cutout.

My next effort will be to check alignment (which will be virtually non adjustable) by using two trunnions with only 3/8" holes. I expect the measurements to be the same as just seen.

[claimdude]

Good stuff Dusty!

Jack

[reible]

I had one of the "bad" parts on the 510 that I got. I didn't know it and all I did find was that it was difficult to align. Yes it would align but it took much longer then I'd come to expect. That also maybe the reason I disliked the 510 as much as I do.

When I upgraded to the 520 it still wasn't easy or quick to align. The other machine was..... so when it came out that some of these were mis-drilled I checked and found I was one of the lucky ones.

When I drilled out the two holes alignment was much easier and quicker. If I got another machine with the small holes I'd drill them again.

Now I don't attempt to center the blade, it is in general "centered" but I see no advantage in having yet another thing to try to adjust to. The most critical parts of the alignment have no bearing on the centered aspect. I guess if I could see an advantage to having it centered I consider it a part of a tune up but as of now I just don't see a reason.

Since there are a lot of tolerances involved any particular set of parts might align fine with the tight holes where another one will not. Since this is the case it makes me think that it is also possible that the location of "center" will not be the same on every machine and shopsmith doesn't care as evident with the various spacers they ship for between the headstock and the carriage.

Anyway I wanted to point out that I was able to get alignment with the small holes but it took longer to do so and was much more of an effort.

Ed

[jsburger]

I had one of the "bad" parts on the 510 that I got. I didn't know it and all I did find was that it was difficult to align. Yes it would align but it took much longer then I'd come to expect. That also maybe the reason I disliked the 510 as much as I do.

When I upgraded to the 520 it still wasn't easy or quick to align. The other machine was..... so when it came out that some of these were mis-drilled I checked and found I was one of the lucky ones.

When I drilled out the two holes alignment was much easier and quicker. If I got another machine with the small holes I'd drill them again.

Now I don't attempt to center the blade, it is in general "centered" but I see no advantage in having yet another thing to try to adjust to. The most critical parts of the alignment have no bearing on the centered aspect. I guess if I could see an advantage to having it centered I consider it a part of a tune up but as of now I just don't see a reason.

Since there are a lot of tolerances involved any particular set of parts might align fine with the tight holes where another one will not. Since this is the case it makes me think that it is also possible that the location of "center" will not be the same on every machine and shopsmith doesn't care as evident with the various spacers they ship for between the headstock and the carriage.

Anyway I wanted to point out that I was able to get alignment with the small holes but it took longer to do so and was much more of an effort.

Ed

Right on Ed. Maybe this will put to bed the centering issue of the blade but I doubt it.

We all know that the designers/engineers have to take into account the tolerances of the individual parts so that when they are put together those variances do not make the tolerance of the final assembly fall outside it's spscs (stack up).

The rubber bumper, that is supposed to give the spacing for the blade, is up against two non machined castings And as we know has been all over the place on width.

[dusty]

For those interested, the naysayers included, the method for table alignment described above works BUT only if you are willing to accept precision to within 1/64". Aligning this way does not provide for tweaking to precisely center the blade but it does square the blade.

While playing with this, I equipped a table with two trunnions that had not been redrilled (all four holes = 3/8"). Installed this way there is no opportunity for changing alignment. You get whet you get. The span from the left face of the blade to the left edge of the left miter track is 4 17/64".

This places the left face of the blade 1/64" to the right of the centerline on the table cutout. My rubber bumper is 1 3/8" wide. The quill is fully retracted. All locks are secure. The table tilt is square to the blade. I am using a standard Shopsmith Table Saw arbor on a blade with a 1 1/4" bore.

I did this on two different table systems but on the same carriage.

That's my story and I am sticking with it.

[reible]

Keeping in mind a typical number we use here for alignment is .005" and 1/64" is .015625" or about 3 times more...........


Again I have no precise number to give as to what is good enough but I do think a 1/64" is not good enough. Just my opinion but I'm sticking to it.

Ed

[dusty]

Keeping in mind a typical number we use here for alignment is .005" and 1/64" is .015625" or about 3 times more...........


Again I have no precise number to give as to what is good enough but I do think a 1/64" is not good enough. Just my opinion but I'm sticking to it.

Ed

I strongly believe that 1/64" precision is as good as you will find on most Shopsmiths that are in service today. But, I know that in itself does not make 1/64" an acceptable standard and I was not trying to do that. I was just saying that with no tweaking available, 1/64" is what I got.

I would have done measurements with a dial indicator so that I could list more accurate numbers. This is what I could see on my steel rule. All of my more precise measuring devices are packed in preparation for the move.

Until I discover a reason why I should not, I am leaving one of my Mark Vs setup this way. A few hours of use will tell me if this is good enough (for me). Yes, I said that. One sixty fourth inch precision just might be good enough for me. Yes, I am one who has touted .005" of accuracy for all but especially for table alignments.

Thanks, Ed for your candid comments.