Replacing spindle or bearings on PM 3520B?

[Dan Forman]

Some time ago I had a chuck unwind from the spindle while the lathe was in reverse. It did a number on the threads before it came to rest. I cleaned up the threads with a file, and didn't really notice much of a problem with my four jaw chucks outside of a little vibration at times chile mounting them, it seems that my collet chuck no longer runs true. I use the collets mostly for precision work in pen making, where a little runout can cause a big problem, especially with drilling and tapping threads. So I think it's time to replace the spindle.

I have no idea how to go about this, it appears the main problem will be pulling and reinstalling the bearings. I called and spoke to one of their techs, who said this would be hard to do without the proper tools and some experience. Have any of you ever done this operation? I did manage to install a Byrd cutter head on my jointer/planer, but there was more room to work in that situation, the lathe head seems like pretty tight quarters to work in. I'm checking to see if there is a repair person in town who would do a "house call", because the lathe is in my basement, and I really son't want to remove the head and get it up, then back sown the stairs.

So I''m wondering if any of you have had to change bearings or the spindle on your 3520B's, and if so, how have you gone about it? Have you done it yourself, or hired it out?

Thanks,

Dan

[Hayes Rutherford]

Sorry to hear it might come to that. Have no experience changing out a spindle on a 3520B but would like to know how. I would think that if the shoulder is square and you haven't changed the outside diameter of the threaded portion, you would still be o.k. I have had more than one mishap with chucks but the only thing that ever caused any run out was the little washer I received with a more recent chuck purchase that is aimed at keeping your chuck from getting stuck.

[Thom Sturgill]

Dan, Nate Davey posted a tutorial http://www.sawmillcreek.org/showthread.php?155720-How-I-Changed-Jet-1642-Bearing on replacing the bearings on the Jet 1642. That might help give you an idea of what would be required. I know that the exact placement of parts is different, so the process would vary some, but in general it should be close.

[Harry Robinette]

I did my General 160-18 when I changed it from a 12" to a 18" lathe and it was real close to Nate's tutorial. I would think you could do this with the general instructions Nate gives.

[Reed Gray]

I wore out the bearings on my 3520A. I took it to a local tool repair store that I have done a lot of business with. I bought the bearings locally, and had them installed for less than I could get the parts for from PM/Jet. They told me that things were pretty much rusted into place, most likely because of all the wet wood I turned. The bearings need to be pressed in, and I would not even think of taking on that type of project. Oneway and Robust have headstock bearing/spindle assemblies that can be unbolted, rather than removing the entire headstock.

robo hippy

[Dennis Ford]

Before you go to the trouble and expense of replacing the spindle; consider working on it a little more. The threads being banged up should not cause run-out. The run-out is likely caused by damage to the shoulder or to the boss. You should be able to dress these up with a sharp scraper at a fairly slow speed (keep the tool-rest very close).

[Dan Forman]

Thanks for the responses. The shoulder and boss are ok, but I think the diameter of the threads has been altered, there is a lot of play before a chuck snugs up. The collet chuck needed a nylon anti locking washer (like Hayes mentioned) in order to run true (within .001") , as the threads weren't deep enough for it to register against the spindle shoulder. Now with just one washer its way off, with two washers it does better (about .004") but not good enough for kitless pen work.

From the link that showed the process for changing bearings, it doesn't look all that difficult, so think I might give it a go myself, but I do have the number of a guy who will make a house call, and will probably check with him to see how much he would charge for the work. If it's not too much, I might have him do it, and watch in case I need to do it again later down the road.

There is another possibility, and that is that the threads inside the collet chuck are breaking down a bit too, and that could be another source of the problem, but I don't remember the body of the chuck wobbling as much as its doing now. Looks like it could be one, the other, or both causing the runout. I guess I'll need to replace the collet chuck anyway, and I'm concerned about long term wear and tear on my other chucks with the spindle threads being in the shape they're in, so I probably should replace both.

I'll keep you posted on my progress.

Dan

[Bruce Stangeby]

I have replace the shaft and bearings on the Powermatic 3520B and did not find it all that difficult. I don't know what " proper tools" the tech rep was talking about, there is nothing needed that I didn't already have. I think the directions in the Jet 1642 tutorial would work just the same on the Powermatic. I was not a big job.

Bruce Stangeby

[Kyle Iwamoto]

How bad are they messed up?
You can try getting a die for the spindle and running it down cleaning up the threads. Cheaper than replacing the spindle, may be worth a try. If just the top 1 or 2 threads are messed up, it may be salvageable.

[Rick Markham]

I thought I had made a reply to this thread last night, but I guess I didn't punch the post button. I measured the diameter of my spindle at the threads and it comes out to 1.2305" (according to my Starrett calipers) That at least gives you a reference point Dan. I'd measure and see if you lost any of the diameter.

[Brian Ashton]

Before you go changing the shaft can you try the chuck on a different lathe, or can it be screwed onto the outboard side and checked. At least that way you can eliminate the chuck as a problem.

If it is for sure not the chuck and you say the shoulder of the shaft is running true (though this would be hard to truly gauge without a dial indicator) then it sounds like the threads are slightly out of round and pushing the chuck to one side. If that's the case I'd try tuning up the damaged threads a bit more.

[Dan Forman]

Rick --- Thanks for chiming in. I measured 1.232" as the thread diameter. It doesn't look like the diameter has changed, but I wonder if what I took off from the sides of the threads would make a difference? I should ask my machinist nephew, he just got his degree in physics last year. :)

Brian --- Our turning club has a PM lathe that resides at our local Woodcraft, I should try the chuck out on that and see what the outcome is. Thanks for the suggestion. Won't have time until the weekend though.

Dan

[Rick Markham]

Dan I would think if you lost enough of the thickness on them then it would allow the chuck to cant slightly which would induce runout or vibrations. My guess (and this is speculation on my part) the width of the thread is more important than the depth, I think the mating surfaces of the threads is probably the most critical part of the equation. but like I said, that's just a guess on my part. You will have to let me know what your nephew says.

[Tim Rinehart]

Dan, FWIW, if you do decide to change out the spindle, be sure to consider changing out the belt at the same time. If you've put alot of miles on this lathe, it would be prudent to also consider changing out the bearings.

[Rick Markham]

That's a good point Tim, might as well get everything taken care of in one shot. I'd loctite the set screws on the RPM thingy (yes.. yes... technical jargon :D) while I was in there too ;)

[Chris Stolicky]

I had a scraped taper from the beginning but lived with it, but when someone else was using my lathe in reverse (not me, no, really!) the exact thing happened. Anyway, I replaced the spindle and bearings on my 1642-2. In total, it took me about an hour taking my time through the process. I could do it much faster the second time around. I did figure out that it was easier to take the front panel off in order to get better access.

It is funny how the instruction book mentions changing the spindle, and then cautions that a qualified person should do it. However, it then goes on to say something like this: 'Here is how it is done anyway....' and then sort of walks you through the process.

[Nate Davey]

Dan,

Rob and I just did the bearings on his Jet, took about 30 minutes. I've unspun a chuck before, the spindle is extremely robust so would doubt it's the spindle. I had a chuck insert go out on me. If your chuck uses an insert try a different insert to see if that corrects the problem. If you're replacing the bearings, you'll need to pull the spindle anyways, you may be able to take it to your nephew and have him check it for accuracy. Good luck