Main Table Alignment Fun

[algale]

Before today I have never had to do a main table alignment. When I bought my previously owned 520 in January 2011, I got it home and checked the alignment of the blade to the miter gauge using a dial indicator in the miter slot (the basic "A-Line It" http://www.in-lineindustries.com/alineit.basic.html has a "smart bar" that can be adjusted for a snug fit in the Shopsmith miter gauge slot) and it was good so I have never had to adjusted it. Until today.

Today I was working on a project and during a cross cut on the table saw of a piece of oak stock about 1.5 inches wide 8 inches long and 0.75 inches thick I could both hear and distinctly feel the teeth at the back of the blade catching and cutting a second kerf as I pushed the piece all the way through. Well, I knew what that meant. The blade was heeled (not parallel) relative to the miter gauge slot. Time to do my first main table alignment.

So, out came the manual. After making sure I thought I understood the steps involved, I confidently set to work on the job.

Four hours later , after many cycles of loosening of trunnions, adjusting the table, tightening the trunnions only to find that the tightening moved the table, and staring over again I finally managed to get the miter slot aligned with the blade to 0.001 inches (per the dial indicator measuring off of the same spot on the blade, which I rotated to the front and back by hand).

This was accomplished only with a lot of trial and even more error, several skinned knuckles, a significant amount of foul language and, ultimately, just a heap of plain old fashioned dumb luck.

In the event I need to do this job again, I have to ask the experts on this forum: is there a better way?

[tnerb]

You did good to get it to .001.

I'm happy to get mine to .002-.004.

The procedure you used is the same one I use. I don't think there's another, easier way to align the main table.

I've found that if the bolts are just snugged at first, then tightened a bit more on sucessive passes, the table tends to stay put.

Brent

[dusty]

You did good to get it to .001.

I'm happy to get mine to .002-.004.

The procedure you used is the same one I use. I don't think there's another, easier way to align the main table.

I've found that if the bolts are just snugged at first, then tightened a bit more on sucessive passes, the table tends to stay put.

Brent

Oh yes there is. I'm not sure you'd get .001"-.002" accuracy but better than .005" is a snap.

http://www.shopsmith.net/forums/showthr ... light=main

The piece of aluminum can be replaced by a block of wood cut square and the V120 can be replaced by the SS Miter properly adjusted.

[algale]

Just watched Sawdust Session #1 http://www.shopsmithacademy.com/SS_Arch ... gnment.htm where Nick covers this. He manages this in a little under 23 minutes, compared to the 4 hours it took me. From a technique standpoint he doesn't really do anything different from the method I used, which is the same technique shown in the manual just substituting a dial indicator in the miter slot for the Allen Wrench through the miter gauge trick.

So why the huge time savings? Because he cheated! He glossed over what was for me (and apparently him) the hardest part, which is keeping the table aligned while you tighten the trunnion bolts.

After loosening the trunnions and purporting to align the table to within "two thousandths" (.002), he goes to snug up the first trunnion bolt and, what do you know, the table moves on him as he tightens it. In a somewhat surprised tone he states that the table has moved while he was snugging up that first bolt and that "ordinarily I'd have to go back and get out the [dial indicator] gauge and do this all over again, but we'll just continue along here."

Then he finishes snugging and tightening everything up. When he's all done tightening, he decides to check the table alignment "just for giggles" and his readings show that the table is now off by twenty thousandths (0.02) and so he'd "have to do this all over again" (no kidding) but "that's all there is to it."

I really admire Nick and think he is terrific. I also understand that they were just trying to demonstrate the technique and that time constraints (and the utter boredom of watching someone wrestle with the trunnion bolts for a couple of hours) make it impractical to show him aligning the table for real from beginning to end in real time. But in this instance I think he and they greatly underplayed just how difficult it can be to get the table to stay put while you tighten those trunnion bolts.

[dusty]

It is a tedious procedure and unless you are incredibly lucky can be very time consuming. But it doesn't have to be.

The next time you have to do that alignment, use the procedure I use and the
time that would have been spent tightening trunnion bolts (without moving the table) can be used for making saw dust.

[algale]

Oh yes there is. I'm not sure you'd get .001"-.002" accuracy but better than .005" is a snap.

http://www.shopsmith.net/forums/showthr ... light=main

The piece of aluminum can be replaced by a block of wood cut square and the V120 can be replaced by the SS Miter properly adjusted.

Leave it to Dusty! OK, I read your post and I agree that it would be a very fast and plenty accurate way of aligning the table to the miter slot. But, if I am following you correctly, there's nothing inherent in the technique that necessarily prevent the table from moving when you go to tighten those trunnions bolts.

On the other hand, I gather that your results were very acceptable so the table obviously didn't move to a significant degree when you tightened those bolts. So, was it the aluminum block, something else, or just luck on your part that the table didn't jump all over the place while tightening those darned trunnion bolts like what happened to me (and Nick).

[Culprit]

Would it work to use lock-tite between the table and trunnions? Not on the bolt threads as it is designed to e used. One of my other hobbies is a 1976 Harley Ironhead. I practically have to use lock-tite on the gas cap to keep it from falling off between fill ups, so lock-tite ranks right up there with duct tape and zip ties in my mind.

Put lock-tite between the table and trunnions, snug the bolts and do your alignment. Then leave the whole thing alone for the cure time of the lock-tite (i.e. overnight). Then come back and put the final torque on the bolts. Yes overnight is longer than the trial and error method, but less stressful. I've never tried this, but am just thinking out loud here.

Other ways to mitigate (not necessarily remove) the hassle is using two polished washers and a thin film of oil to reduce friction and reduce the tightening torque from moving things out of alignment.

[dusty]

Leave it to Dusty! OK, I read your post and I agree that it would be a very fast and plenty accurate way of aligning the table to the miter slot. But, if I am following you correctly, there's nothing inherent in the technique that necessarily prevent the table from moving when you go to tighten those trunnions bolts.

On the other hand, I gather that your results were very acceptable so the table obviously didn't move to a significant degree when you tightened those bolts. So, was it the aluminum block, something else, or just luck on your part that the table didn't jump all over the place while tightening those darned trunnion bolts like what happened to me (and Nick).

No! The table moved. I quickly relocated it and reattempted the tightening procedure. Only two screws are accessible without changing table tile. I position the table and then very carefully snug one screw and then the other, then the first (a bit more) then the second (a bit more) constantly rechecking the visual alignment. Once the two left screws are TIGHT, I check the visual and then tilt the table to tighten the other two right screws. Finally, a visual check and Make Sawdust.

It takes some time but it is not as tedious and I believe it is every bit as accurate.

[dusty]

Would it work to use lock-tite between the table and trunnions? Not on the bolt threads as it is designed to e used. One of my other hobbies is a 1976 Harley Ironhead. I practically have to use lock-tite on the gas cap to keep it from falling off between fill ups, so lock-tite ranks right up there with duct tape and zip ties in my mind.

Put lock-tite between the table and trunnions, snug the bolts and do your alignment. Then leave the whole thing alone for the cure time of the lock-tite (i.e. overnight). Then come back and put the final torque on the bolts. Yes overnight is longer than the trial and error method, but less stressful. I've never tried this, but am just thinking out loud here.

Other ways to mitigate (not necessarily remove) the hassle is using two polished washers and a thin film of oil to reduce friction and reduce the tightening torque from moving things out of alignment.

The bolts that secure the trunnions to the table are embedded into the cast aluminum table. I do not believe that putting loc-tite on those screws would be advisable. I am not certain how well that cast aluminum threads would survive. If those threads go bad I think it is new table time.

Hmmm, having said that - would JBWeld work??? Could I fill the hole with JBWeld and then drill and tap a new hole?

[algale]

I believe it is every bit as accurate.

Agreed. As Nick explained in the Sawdust Session on main table alignment, once you have the blade aligned to miter slot to the point where the front to back error on the blade is less than half the width of the blade's tooth's overhang (set?) beyond the blade's plate, there is no added kickback risk as compared to a blade that is more perfectly aligned to the miter slot. After that point, all you are really doing by trying to get closer alignment to the miter slot is chasing a smaller kerf width, since even a severely heeled blade will cut a perfectly straight line (at least until you heel it so much that the back of the wood hits the blade's plate, rather than a tooth).

Yet even though I know it is not really necessary, I still pull out the dial indicator and try to get as close that that elusive zero error as possible. Thank goodness that my dial indicator is only graduated in thousandths of an inch (0.001) rather than in ten-thousands of an inch (0.001). I'd probably still be at it (or, more likely, hanging from a rafter in my basement).