Trouble with Trunnions

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SASman
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Trouble with Trunnions

Post by SASman »

Hello all,
I’m progressing on my fixing/retuning of my new/old 510. So far so good. I’ve replaced the miter gauge, the old one had missing parts and one piece of the handle was broken. Waiting on a fence, same reason. Had fun cleaning and waxing the table and extensions. Today I cleaned and waxed the bench tubes and way tubes. That had been the biggest change for me. I no longer risk my back pushing the carriage and headstock along. Slides easy-Peasy now.
I have, however a couple of other questions. First, I have 2 different spindle knobs on the auxiliary spindles. One is short and closed, like a bottle cap. The other is longer, open through and has a reduced diameter section. Is it important which one goes on which spindle end?
Spindle knobs
Spindle knobs
46A5F76C-0E83-4650-9DBE-5689DF033A00.jpeg (486.58 KiB) Viewed 1355 times
Apologies for the upside down pics. Can’t figure out how to turn them.
Second and more concerning question has to do with the trunnions on the table. After releasing the table tilt lock, I can move the table to the 90 degree end but with difficulty. Moving to the 45 degree point on the other side is almost impossible. I don’t see any thing that might be a cause, everything looks clean, no impacted sawdust. Here are a couple of pics back and front.
Rear trunnion
Rear trunnion
71BC56E5-4384-4A93-9B4B-AF9A821EF60B.jpeg (572 KiB) Viewed 1355 times
Front trunnion
Front trunnion
A9854395-B6BD-4DE7-8E76-BFBC3D43839A.jpeg (516.7 KiB) Viewed 1355 times
Another odd thing about this. The front trunnion doesn’t have a 90 degree stop button, so I can’t simply align my 90 degree mark. Buuuut, the back trunnion does have a 90 degree stop button. Weird. I’m having trouble trying to figure out how the prior owner might have done that.
Any ideas would be appreciated.
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dusty
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Re: Trouble with Trunnions

Post by dusty »

I'll start with the easy one. Take the trunnions off and exchange the front and rear. The one and only button should be on the front. The trunnions don't look bad, Make sure the locking mechanism is loose when trying to change table tilt. Don't was the trunnions. You might want to pull the locking mechanism off and check the facings for burrs.

The short hub (bottle cap) should be on the lower (idler) drive shaft. The longer (open one) goes on the upper (spindle) shaft. It does make a difference. Check how the sets screws mate with the tappers.
"Making Sawdust Safely"
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DLB
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Re: Trouble with Trunnions

Post by DLB »

SASman wrote: Mon Nov 22, 2021 2:23 pm Hello all,
I’m progressing on my fixing/retuning of my new/old 510. So far so good. I’ve replaced the miter gauge, the old one had missing parts and one piece of the handle was broken. Waiting on a fence, same reason. Had fun cleaning and waxing the table and extensions. Today I cleaned and waxed the bench tubes and way tubes. That had been the biggest change for me. I no longer risk my back pushing the carriage and headstock along. Slides easy-Peasy now.
I have, however a couple of other questions. First, I have 2 different spindle knobs on the auxiliary spindles. One is short and closed, like a bottle cap. The other is longer, open through and has a reduced diameter section. Is it important which one goes on which spindle end?

The one with the closed end goes on the lower aux spindle. Avoids interference with the vent plate.(?) I'm not sure on that reason.

Apologies for the upside down pics. Can’t figure out how to turn them.
Second and more concerning question has to do with the trunnions on the table. After releasing the table tilt lock, I can move the table to the 90 degree end but with difficulty. Moving to the 45 degree point on the other side is almost impossible. I don’t see any thing that might be a cause, everything looks clean, no impacted sawdust. Here are a couple of pics back and front.

The trunnions may be 'tow in/out' slightly, rather than parallel. First thing I would check is the hole size for the table mounting bolts. Some trunnions have smaller holes and this can cause some binding when aligning the table for miter slots parallel to blade. If some of your trunnion holes are small (3/8 IIRC) tell us which ones and let's see about a consensus or multiple opinions on what to do about it. If that is not the cause, then there is a Sawdust Session that includes what is known as the $20 bill trick. That also reduces binding. In your case I'm thinking it is the undersized holes.

Another odd thing about this. The front trunnion doesn’t have a 90 degree stop button, so I can’t simply align my 90 degree mark. Buuuut, the back trunnion does have a 90 degree stop button. Weird. I’m having trouble trying to figure out how the prior owner might have done that.
Any ideas would be appreciated.

The button itself can be installed in either trunnion, but it only works if it is in proximity to the stop bolt though, which is at the front. The trunnions themselves can also be swapped, though more disassembly is required to do so. The best solution here might depend on the hole size question above. IIUC it is 'normally' the rear trunnion that has the small holes. That's true for me, sample size of one. Which may not matter depending on the consensus resolution. But my preference, until proven wrong, is to leave one undersize hole and enlarge the other only slightly.
- David

EDIT - Correction - The table tilt 0 degree stop button cannot be readily installed in all trunnions. While the hole and out side counterbore are the same, some rear trunnions do not have the inside counterbore to allow button installation.
Last edited by DLB on Sun Dec 05, 2021 2:40 pm, edited 1 time in total.
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dusty
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Re: Trouble with Trunnions

Post by dusty »

I'm curious. How would the 3/8" trunnion holes introduce binding in the table tilt?

The discussion on the size trunnion bolt holes is warranted but it should only involves problems with table alignment NOT table tilt.

As far as hole size - I enlarged mine. All of my trunnions now have 1/2" holes and I regret having done that. I've given thought to putting in shims. As it is, I loosen all the bolts and push the table hard right against the bolts. This givers me nearly perfect alignment (table tyo blade).

I can go by only the two machines that I have but the "Horizontal Lock Button" engages with an adjustment screw and there is only one of those and it is located on the front end of the table tie bar.
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SASman
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Re: Trouble with Trunnions

Post by SASman »

To answer the last question first, I think what’s happened is when aligning the table, you can get more movement with the larger holes in one trunnion but that could be constrained by the lesser movement allowed by the smaller holes in the other trunnion, putting stress somewhere in the structure. In my case I guess it compressed the trunnions against the stop blocks at the farthest points of movement.
And I did pull off the table top and the front trunnion holes were .37(3/8”) and the back trunnion holes were .50(1/2”).
So it looks like the trunnions were switched front to back, if what Dlb says is true.
I’ll try first just screwing them back down and see if that helped. Of course then I’ll have to realign the table which might reintroduce the problem. We’ll see. More later.
SASman
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Re: Trouble with Trunnions

Post by SASman »

And apologies. In my first post when I talked about the 90 degree stop button, I meant the center (0 degree) level table point. Sorry for the confusion.
DLB
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Re: Trouble with Trunnions

Post by DLB »

dusty wrote: Mon Nov 22, 2021 4:14 pm I'm curious. How would the 3/8" trunnion holes introduce binding in the table tilt?

The discussion on the size trunnion bolt holes is warranted but it should only involves problems with table alignment NOT table tilt.

As far as hole size - I enlarged mine. All of my trunnions now have 1/2" holes and I regret having done that. I've given thought to putting in shims. As it is, I loosen all the bolts and push the table hard right against the bolts. This givers me nearly perfect alignment (table tyo blade).
If only I had your drawing skills... So, consider that recent Ed Reible experiment. He has four 1/2" trunnion holes so the table moves freely 1/16" in any direction when the bolts are loose, essentially a 1/8" circle of play. Change that to three 1/2" holes and one 3/8" hole and the movement becomes more like a short arc because the bolt through one small hole acts like the fixed point on a compass. With two 3/8" holes, which I now think is the 'other' real world case, the table won't want to move at all but you have a lot of leverage so it still arcs. (I tried this, but didn't measure the arc.) My theory is that will put the rear trunnion in a bind when you tighten the bolts. How much of a bind depends on individual table alignment, so from none at all to a lot. The other thing is it may pull the table back out of alignment some when you tighten those close fit bolts, so tightening sequence will be a factor in what you end up with.

There is nothing wrong with an arc from an alignment perspective. We're setting an angle, offset front/back and left/right is pretty useless. So while two 3/8" holes is reported to sometimes cause problems, my current thinking is that one 3/8" hole is desirable. Especially if it is on one of the bolts that you have to tilt the table to tighten. (In the Sawdust Session on main table alignment (Session 1 Topic 2, which includes the $20 bill trick) Nick recommends snugging one bolt for a similar effect.)

- David
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dusty
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Re: Trouble with Trunnions

Post by dusty »

I agree. If you can rotate the table about one bolt (3/8") you can probable get alignment. If I was going to do this, I would choose the right front bolt.

PS: Actually - I am in error here. The drawings depict movement about the left rear trunnion bolt.

However, please ponder these sketches which are intended to depict movement of the table about the right rear trunnion bolt. Note the minimal amount of movement about the right rear bolt. At the same time look at what happens on the left side. The difference is because the left side is 14 1/2" away from the pivot point while the right front and rear bolts are only 3 1/2" apart.



Notice How Little Movement there is on the right side. This is why I contend that enlarging only one hole will make little difference.

The degree of rotation depicted here is .2 degrees. Maximum movement at front side about 1/16". Rotate the other direction and see the same amount of movement.

Please ignore the references to right or left and front or rear as used on my sketches here. The labels do not agree with what is depicted in the sketches. I apologize for the confusion this could cause.
Attachments
No Table Rotation.jpg
No Table Rotation.jpg (76.62 KiB) Viewed 1242 times
Front Bolts Rotated.PNG
Front Bolts Rotated.PNG (9.67 KiB) Viewed 1242 times
Front Bolts, No Rotation.PNG
Front Bolts, No Rotation.PNG (9.93 KiB) Viewed 1242 times
Rear Bolts Rotated.PNG
Rear Bolts Rotated.PNG (5.16 KiB) Viewed 1238 times
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DLB
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Re: Trouble with Trunnions

Post by DLB »

Thank you Dusty, I agree. My plan if/when I do this is to enlarge one hole only slightly. Making it 1/2" would be overkill, it will never use anywhere near that even if the front trunnion holes used the full range. I haven't done the math, but I'd want the farthest hole from the center of rotation to be the one that sets the limit. I'm thinking 7/16" or slightly less depending on what drill bits the user has available for metal.

SASman - Note that swapping trunnion front to back is very easy while the table is off. Loosen the tilt lock and the trunnion will roll 180 degrees and then slide right off its hinge pin. Probably how your PO did it. ;)

This is the very old (in forum years) thread mentioning trunnion hole size, $20 bill trick, even one user confirming that his small holes were on the rear trunnion: viewtopic.php?f=5&t=131&start=10 Increasing my sample size to two.

- David
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dusty
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Re: Trouble with Trunnions

Post by dusty »

Just a point of clarification. My sketches are intended to depict rotation of the table about one trunnion bolt. That small dot in the middle is not the axis of rotation.

My apologies to SASman. I certainly pulled this thread off topic.
"Making Sawdust Safely"
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