Palmgren 8" Rotary Table repair

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whateg0
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Palmgren 8" Rotary Table repair

Post by whateg0 »

I bought a rotary table off of ebay a while back and have used it a few times. It gets the job done. But something has always bothered me about it. The tabletop seemed to be off center, and by seemed to be, I mean it is! I took the table off a couple months ago and found that it has two tapered pins inserted 180 degrees apart. Flipping the table 180 degrees got me from about 16 though TIR to under 10. This was measured off the center hole in the table, so it's still not good enough to use to indicate the table in. So, tonight I took it all apart again and man, the things I found out. I thought that Palmgren was a quality tool, so I would like to think that somebody made some changes to the table, but I have no idea why.

First, now that I've had it apart and inspected it, I don't think the tapered pins were put there by the factory. If they were, they were way off.

Second, the bottom of the table has a boss that extends into a recess in the gear/hub. The recess in the hub has right at 0.00088" TIR and measures 1.7537" in diameter. The boss on the bottom of the table, the hole in the middle of the table, and the outside of the table are not concentric. All three have different centers. The boss has a diameter of 1.739" as measured by my calipers. (The calipers also measured the recess at 1.750". I need to double check something there.) Regardless, putting the gear on the bottom of the table, there is definitely some movement there. So, the hole-boss is about 0.012" TIR. The hole to outside of the table is about 0.006" TIR. Those two are not in the same direction, like about 45 degrees apart.

So, is this typical for a Palmgren rotary table? Doesn't really matter at this point, but I'm curious.

The plan is to bolt the table to the faceplate on the lathe so that the perimeter is dialed in. Then bore it so that the center hole is in the center. Oh, and make it a nominal size. As it is now, it mic's 1.017" Then turn a mandrel and turn the outside of the boss down so I can fit a ring between it and the recess in the gear/hub. I can't do it all at once because the bolts will be in the way unless I drill some new holes. I guess I could do that and then tap them for some set screws. Now that I think about it, that might be the better way to go so that both of those features can be turned in one setup.

Anything I missed?
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Harold_V
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Re: Palmgren 8" Rotary Table repair

Post by Harold_V »

Considering the less than good report you provided, I think you'd be well served to start with a determination of the true centerline of rotation. It may not be concentric with the existing OD. Do that by cranking the table with a DTI on the perimeter. If it checks out, you're golden. A setup on a lathe, or even dialing the perimeter true, then boring on a mill, would work fine. And, I agree with your decision to shoot for a nominal, commonly seen size. The hole in my 12" BP table is 1", and very useful.

Harold

edit: I suspect you know better than to use calipers for this operation. They are not capable of providing reliable information, so the work you do will be suspect. A telescoping gauge is well within your needs, assuming you've used them before, and know how to use them accurately.
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whateg0
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Re: Palmgren 8" Rotary Table repair

Post by whateg0 »

With nothing holding anything true, the centerline of rotation can be just about anything. I can bump the table 5 or 10 this way or that. I kind of wonder what somebody was doing before that caused it to get so out of whack. My guess is that's why they thought the tapered pins would be a good idea. Don't know for sure, though.

I hadn't really thought of doing on the mill. Lacking a DRO or coax indicator, it's a little tougher to dial it in. Plus it's a round column mill, so I only have so much Z. I could set up one of the DTI on a bar in the spindle, though. I wouldn't need to turn a mandrel for the lathe. Yeah, the mill does seem like a better option now.

Thinking about this now, it's always seemed like I had to back the locks way off or it would get tight somewhere.
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Harold_V
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Re: Palmgren 8" Rotary Table repair

Post by Harold_V »

Strikes me odd that there's no register that keeps the table on center. Without one, I'm not sure I understand what the design was intended to do.

Can you post a couple pictures of the bottom of the table (the part that turns, not the bottom of the base) and inside area, where it's intended to run? I can't help but think something's amiss. Or, maybe, I don't understand what I'm reading. :-)

H
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pete
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Re: Palmgren 8" Rotary Table repair

Post by pete »

That depends. Is the center hole a Morse Taper? If so be real careful, there may not be much metal in a lot of areas. By the sounds of it I'd almost bet on it. But if it were me? I'd check the tables bottom on a very lightly blued surface plate to establish how flat that is first. Then once that is I'd check the tables surface elevation on that surface plate at various points. Don't rotate the table just move the indicator around the table. You want to check that the table surface is parallel to the bottom surface.My little 6" Vertex is about 4/10ths off on the Morse Taper and just about a thou on the table perimiter. But it's at least only a 10th or two out for flat. I keep a slip of paper with the tables degree points for where and how much it's out in case anything really fussy needs to be done when I'm indicating the table to the spindle C/L.

Palmgen was ok at one time but I think everything they now sell is offshore. For years I lusted after one of there X,Y rotary tables that cost a lot back in the early 1980s. Once I got a mill then all I needed was a standard R/T. Now I seriously would like one of the Troyke R/T's that have the X,Y table on the top of the R/T for making offsets and arcs a lot easier.
whateg0
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Re: Palmgren 8" Rotary Table repair

Post by whateg0 »

Harold,

I believe that the center boss in the top photo was supposed to be a close fit to the recess in the gear in the bottom, but at some time it was modified. No idea why, though.
assembly.jpg
whateg0
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Re: Palmgren 8" Rotary Table repair

Post by whateg0 »

Pete,

This isn't some new table. It's old. I just assume that anything new I can afford is probably less that stellar in terms of quality. There's no taper. just a round hole through the table top, so that chips can get down in between the top and the gear. (I actually made a plug to go there, but there were already a bunch of chips in there.) The table is pretty flat. I haven't put it on a surface plate and mapped it, but a cut around a part into a spoil board yielded a uniform groove all the way around. That isn't the problem, and for that to cause 0.010" TIR it would have to be wobbling like a carnival ride! No, it's just off center. The measurements prove that in more ways than one. The raised area in middle of the photo below fits into the recess in the gear/ hub, but it's got a lot of play that I don't think should be there. And the hole in the middle is not concentric to the outside of the table.
tabletop.jpg
I can measure the "thickness" of the table between the hole and the perimeter and it's not close to the same all the way around. I'm 100% certain that it's not right. I was just wondering if this type of workmanship was typical of Palmgren, or if this table has been altered. I'm leaning toward the latter.
whateg0
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Re: Palmgren 8" Rotary Table repair

Post by whateg0 »

I don't have any pics of the table assembled, and right now, it's a pile of parts, aside from those in the bucket of degreaser. Here's a table much like mine, except mine is 8" instead of 10".
Palmgren-10-horizontal-vertical-rotary-table.jpg
Palmgren-10-horizontal-vertical-rotary-table.jpg (35.37 KiB) Viewed 3588 times
The bottom of my table looks like this.
ahe135-palmgren-8-horizontal-vertical-rotary-table-862-9-resize.jpg
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Harold_V
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Re: Palmgren 8" Rotary Table repair

Post by Harold_V »

I suspect a repair would be dead easy. Now that I've seen it, I think I'd simply chuck up the table, dialing the OD true. I'd then turn the portion that should be the register, to ensure it's concentric with the OD. I'd then determine the center of rotation, likely the diameter beyond the teeth. Set up to that location, bore the existing hole to accommodate a sleeve, which would have to be a press fit either on the table, or the bore. A thou of clearance, after assembly, and the table should be just fine. Probably easiest to do the base first, and make the sleeve a press fit with the table. That way you and machine the created sleeve after it's pressed on, to ensure a proper fit. Probably ignore the pins---and plug the holes if they're a problem.

Harold
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John Evans
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Re: Palmgren 8" Rotary Table repair

Post by John Evans »

Palmgren = US made Chinese in my experience ,either older or newer . Any of it comes my way ,it just keeps moving on.
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Rich_Carlstedt
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Re: Palmgren 8" Rotary Table repair

Post by Rich_Carlstedt »

Not true about older palmgrens.
I know, I did some repair work on one of their surface grinders back in the 70"s
They were at 8383 South Chicago Ave. in Chicago ILLinois .
They were bought out by the Hanson tool company a few years back , so who knows what happened then.
I can tell the poster that i doubt the 'modifications" he experienced were of a factory nature or change.
Yes, they are not Troyke or Brown and Sharpe in quality as their focus was on affordable tooling , but the errors he noted and expressed are way out of the ballpark.
Rich

PS I took the previous post as meaning made in China and that was my point, they were made here at least back a few years ago
The quality level was not meant to be top of the line.
whateg0
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Re: Palmgren 8" Rotary Table repair

Post by whateg0 »

I got started on the fixes tonight. Indicated the table in on the mill and bored the center true to the outside. I have chosen to get the table right first, as it's the less accessible of the two parts that matter. In fact, I'm not really sure how to measure the part that extends out from the bottom of the table. Best I can really do is calipers. The mic won't fit down in the recessed area. So, the plan is to get that part turned down on the mill to "a size" that I can make a press fit sleeve for. Then turn the sleeve to fit whatever it ends up being. I may do some of what Harold suggested, in indicating the gear so that I'm on its center of rotation. Then I can turn the bore the center recess of the gear to concentric. That might get done on the lathe as it's easier to indicate the part in. Shouldn't take more than a skim pass to make it right, as I only got less than 0.001" TIR there. I'll make the sleeve a close fit for the gear when pressed onto the table. That's a bit backward from Harold's suggestion, but without a good way to measure the bottom of the table with confidence, I don't want to end up back where I started.
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