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Discussion Starter · #1 ·
I recently took apart my table saw in a renewed effort to get to the bottom of an issue described in a previous discussion. I've made some headway on that issue and have learned some other things about my saw in the process, but I'm also encountering some new issues. One step forward, one step back.

First off, while reassembling the upper trunnion assembly (referred to as the bearing arm assembly in the parts diagram) I'm having trouble getting the worm gear (#16) and gear segment (#20) for the blade raising to mesh perfectly. I do think I have them centered well and there's no binding or anything when raising and lowering. The movement is fairly smooth and easy as I crank the handwheel. The problem is that if I lift up on the motor or the bearing arm assembly, there's a slight amount of play. From what I can tell, this play is between the worm gear and the gear segment and has to do the positioning of the gear segment. Loosening the hex bolts (#21, #22), the gear segment has quite a bit of movement to change the relationship between it and the worm gear.

My question is, does anyone have any experience or advise on how to fine tune adjust the gear segment to perfectly mesh with the worm gear? I've tried adjusting it a number of times to reduce the slop when lifting up on the motor, but its just a frustrating game of guess and check. I've gotten it pretty close, but cant completely eliminate the slop. I'm just wondering if there's a tried method for dialing this in or of it's just a matter of loosening the bolts, randomly nudging, and checking. I wouldn't be so concerned about the slight amount of wiggle except that I believe it is a contributing factor in another issue I'm having , described in the thread I linked above. I'd also be interested if anyone else has a model 66 and would be willing to check if they have any noticeable movement in the pivot when lifting up on their motor.

Another question I have about the bearing arm is, where is the point of contact supposed to be when the blade is lowered all the way down to it's minimum elevation? I didn't pay attention to this before disassembling, but now that it's back together, I've noticed that the point that limits the bearing arm from pivoting further down is the bearing arm itself bumping into the main trunnion casting under the arbor bearing housing. It seems a little odd that the contact would be between to rough pieces of the castings. The blade height maximum is set by an adjustable bolt (#28) to prevent the arbor or pully from contacting the underside of the table, but I see no such adjustable stop for the lower minimum. This isn't a big concern, but I wonder if others can confirm whether this is by design or if I missed something during reassembly.

And lastly, I'm wondering about the spacers (#41) shown in the parts diagram around the pivot shaft. The diagram below is from a newer version of the saw which shows a spacer on either end of the pivot shaft. Older versions of the manual don't show any spacers at all. My saw, which is possibly a 1987 vintage judging by the serial #, only has one spacer on the nut side of the pivot shaft (right side when standing in front of saw). This spacer looks to be just a large nylon washer to prevent friction as the shaft pivots. I'm wondering if I'm missing a spacer on the left side or if my version of the saw is supposed to have just one. I haven't been able to find a copy of the manual that exactly matches my saw configuration, but I imagine they didn't draw up new diagrams for each incremental iteration of the saw over the years. I'm contemplating ordering two of the spacers and trying that out since it might also help resolve other issues I'm having. If anyone has a newer model 66 that more closely matches the diagram below, I'd be curious of their spacers on the pivot shaft look to be plastic or metallic. Photos of the part I've been able to find online look metallic to me, but the one spacer I have is definitely plastic.

If anyone is curious about the other issues I've alluded to, check out the other discussion. If any of this leads to improvements there, I'll post a follow-up in that thread.

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David - Machinist in wood
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I restored my 1990 PM66 a few years ago but don't recall enough to steer you in the right direction. Here's my restoration thread if you want to glance through and see if anything will help you - Restoration - Powermatic 66 Table saw
 

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Discussion Starter · #3 ·
@difalkner, Thanks doe sharing that thread. I actually came across your post the other day while doing some searching. Great work with the restoration. It does look like we have a similar vintage judging by the shape of the trunnion and the arbor pullies. Do you still use the saw? Has everything stayed nice and true over the years? I wonder if you recall any frustrations with aligning the gears for the raising mechanism or if everything just fell right in place?

Here's a photo to illustrate where my trunnion bottoms out when lowering the blade.
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David - Machinist in wood
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Great work with the restoration... Do you still use the saw? ...I wonder if you recall any frustrations with aligning the gears for the raising mechanism or if everything just fell right in place?
Thanks! It was definitely a lot of work but well worth it. Oh yeah, sometimes daily. Check out some of my videos on YouTube and you'll see it in use.

No, it all seemed to go together as designed with virtually no issues except for all the water damage.
 

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@difalkner, Thanks doe sharing that thread. I actually came across your post the other day while doing some searching. Great work with the restoration. It does look like we have a similar vintage judging by the shape of the trunnion and the arbor pullies. Do you still use the saw? Has everything stayed nice and true over the years? I wonder if you recall any frustrations with aligning the gears for the raising mechanism or if everything just fell right in place?

Here's a photo to illustrate where my trunnion bottoms out when lowering the blade.
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That can't be right, the arbor should center with the cut out in that bracket below.
 

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Discussion Starter · #6 ·
No, it all seemed to go together as designed with virtually no issues except for all the water damage.
Huh, I wonder of you got lucky or if I'm just doing something wrong. Perhaps the gear segment is supposed to register against some feature on the casting to position correctly. I don't recall seeing anything obvious when I had it all out of the saw and was remounting the gear segment though. And it's nearly impossible to get a look at while in the saw.

That can't be right, the arbor should center with the cut out in that bracket below.
Heh, you would think so, but that is actually the correct position of the arbor relative to the trunnion. The blade does lower down past the table as it should. I just find it odd that the lower limit is determined by the castings bumping together rather than something more deliberate like an adjustable bolt like all the other movement limiters on the saw. I'm not sure what the purpose of that cutout is though. I haven't seen it in any of the versions of the manual I've found, although I did see it on @difalkner 's trunnion as well.
 

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Huh, I wonder of you got lucky or if I'm just doing something wrong. Perhaps the gear segment is supposed to register against some feature on the casting to position correctly. I don't recall seeing anything obvious when I had it all out of the saw and was remounting the gear segment though. And it's nearly impossible to get a look at while in the saw.



Heh, you would think so, but that is actually the correct position of the arbor relative to the trunnion. The blade does lower down past the table as it should. I just find it odd that the lower limit is determined by the castings bumping together rather than something more deliberate like an adjustable bolt like all the other movement limiters on the saw. I'm not sure what the purpose of that cutout is though. I haven't seen it in any of the versions of the manual I've found, although I did see it on @difalkner 's trunnion as well.
I looked on the internet and I can't find that cut out on any saw. It just appears the cutout is to leave clearance for the arbor assembly. I'm wondering if the part is off a different model saw.
 

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Discussion Starter · #8 ·
I looked on the internet and I can't find that cut out on any saw. It just appears the cutout is to leave clearance for the arbor assembly. I'm wondering if the part is off a different model saw.
If you have a look at @difalkner 's trunnion, he has the same cutout. None of the parts diagrams seem to have that same shape, but I have seen a few examples of photos that show the cutout as well. I'm pretty confident that its the correct part and in the correct configuration.

 

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If you have a look at @difalkner 's trunnion, he has the same cutout. None of the parts diagrams seem to have that same shape, but I have seen a few examples of photos that show the cutout as well. I'm pretty confident that its the correct part and in the correct configuration.
Yes, the cutout is shown on his saw. Perhaps he will comment how his arbor fits the notch on his saw.
 

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Perhaps he will comment how his arbor fits the notch on his saw.
I don't honestly remember, Steve. Tomorrow I can get to the external drive where those photos are stored and see if I have a better photo. I might be able to take the throat plate off and see inside; if so I'll post some photos but no guarantees I'll be able to see that from the top side.
 

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Discussion Starter · #11 ·
@difalkner I don't think you'll be able to get a good look at that side of the trunnion from the throat. It's only really visible from the left side with the motor cover off. I'm not too concerned about the position of that cutout though since there's nothing I can do about it. It's well over an inch off of center with the pulley so any misalignment I introduced couldn't have affected it that much. It might shed some light in whether I have a Frankenstein saw on my hands, but I don't think that's the case.

I do wonder if you'd be willing to check if your arbor has any play when you lift straight up on it. That might inform me in whether I should be as concerned about the worm gears perfectly meshing.
 

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David - Machinist in wood
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I do wonder if you'd be willing to check if your arbor has any play when you lift straight up on it.
Just checked and there is no play whatsoever anywhere in the trunnion mechanism. I did find an old photo and in using a mirror on the saw just now it appears that when the blade is lowered into the lowest position the pulley does not directly line up with the relief cutout but it also does not hit the trunnion. These photos may or may not help...

Edit - maybe you're one tooth off on engaging the worm gear, if that's possible.
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Discussion Starter · #13 ·
@difalkner Thanks for taking the time to check! It's good to know that there probably shouldn't be any play when lifting the arbor. I'm not sure that the gears could be off by one since it's it's a continuous mechanism and being off by one would essentially just mean the blade is one revolution higher or lower. I'm becoming more and more convinced that the gears just aren't fully and perfectly seated so there's a slight gap between the teeth that allows some slop. I've just gotta work at it some more to get the gear segment seated more snuggly against the worm gear.

It's nice to know that the cutout isn't intended to line up with the pully, even though it looks like it would be a good fit. Who knows why it's there, but this saw was manufactured for quite a number of years and must have seen many revisions that left behind no longer needed features.

Your second photo does seem to answer my question about the spacers on the pivot shaft. It does look to be metallic rather than the plastic washer I have. And the big nut holding it on is quite different than mine. My nut has a nylon ring inside it to act like a lock nut. Since they were inexpensive and I think the pivot shaft is the root of my blade alignment issues, I went ahead and ordered two spacers and a new shaft. The nut and retaining clip on the opposite side were discontinued, but I can get the clip at my hardware store and my existing nut should work just fine.
 
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