D1-4 on a PM1340

[Ken226]

@Tired&Retired You are better off using a piece or rounded wood, wrapped around with emery, than trying to use a compound. It will keep your hands 2-3" away from the spinning surfaces. You can also slow it down to 200 or 120 RPM, and that will feel safer. If you want to get arcane, you can bond the emery to the wood, but it is completely unnecessary..

This is the ideal method in my opinion. It has several advantages, including safety.

The cast iron common in backing plates will quickly wear the sanding abrasives. As the sanding abrasives wear and fill, you can easily rotate the dowel, exposing fresh abrasive material. Then, you can flip it and use the other end.

A rectangular section tool has 2 even smaller contact patches. They would wear and load up very quickly. A dowel is the way to go.


Keep in mind how small the actual contact patch is on a circular section abrasive tool. It's bigger than the corners of a rectangular tool, but still small. Mounted rigidly in the toolpost, You'll be wearing out each spot and having to loosen, rotate and re-tighten alot more often than is necessary.

 

[Tired&Retired]

Success! At least I think so.

First off, in preparation to doing the actual work on the spindle taper:

I wanted to double check all the runout measurements on all surfaces to have a baseline as to what exactly I needed to do. Plus I wanted the Dremel tool mounted to the toolpost to be aligned to the spindle taper as closely as I could get it.

I worked on the lathe a day or two later, and I believe I now have satisfactory results. I was worried about the spread between the 3 jaw chuck's gap (0.002") and that of the 4 jaw chuck (0.008"). But I think I hit the sweet spot grinding the spindle taper for both of them. The 4 jaw chuck seems to fit flush when I crank down the camlocks using a socket driver instead of the key wrench. At least I can't get a 0.0015" feeler gauge between the surfaces. That is the thinnest material I have in order to try to do that. So I am hoping the surfaces are actually clamped together now, and there isn't something like a 0.0013" gap there. I can't see any daylight between the surfaces, but the outside rear lip edge of the chuck doesn't give me a real good angle to see any possible gap very well. Takes some solid whacks with the plastic headed mallet to break it free from the spindle. I didn't want to chance taking off any more metal, but I did polish the spindle taper surface a bit with a very fine grit after checking the fit with the chucks.

With the 3 jaw chuck, it will actually pop loose from the spindle when I loosen up the camlocks but there doesn't seem to be any lateral play at all that I can tell. At least when I put a milling bit in the jaws, the runout hasn't changed at all, even trying all three different positions for the camlocks, so repeatability seems to be OK. I tried different diameter bits in the jaws, and best I could get was around 0.0045" out of any of them. It was most often around 0.006" with most of the different diameter bits I tried. But in any event, I don't believe that runout is being caused by the chuck not fitting flush against the spindle face any longer.

The other two chucks I have remaining after sending others back to the sellers (ER40 and 5C collets) fit snugly and require modest persuasion with a mallet to break them free of the spindle taper. Runout for both of those chucks on the inside surface where the collets reside dramatically improved with that now being right around 0.0005". So that isn't bad at all. For me, anyway. While working on this, I spent considerable time working on that little bit of runout out on the spindle taper noted in the above video and I think that helped make a difference. All in all, I spent roughly 3 days working on this. So obviously I was taking my time.

So it appears I may have this problem behind me now. I am REAL glad I didn't have to replace the spindle. I think that would been a real PITA to do.

Anyway, just providing a followup if anyone is still interested. Thanks for all of the advice and help with this, but I decided working on ONE part (meaning the spindle) was better done than working on all of the chucks.

 

[Procule]

Thanks for posting your journey!

 

[Dabbler]

Thanks for posting a detailed account of your work on this!

So I am hoping the surfaces are actually clamped together now, and there isn't something like a 0.0013" gap there. I can't see any daylight between the surfaces

You can put a thin coat of prussian blue, mechanics blue, etc on the face and ensure you actually have contact.

 

[Nesse1]

This thread resurfacing struck close to home, since I'm having this exact same problem with my lathe (posted in another thread.)

I have one backplate that tightened up okay, but two other brand new units, one part of a PM collet chuck, that won't snug up flat on the spindle nose.

I removed the camlock cams in the spindle and they look galled up, and the machining isn't right on one of them, so I ordered a new set. Fingers crossed they fit. I do think my spindle taper is on the high end of the tolerance window, though.

Some of the photos and videos from this thread are gone now, and I'd appreciate a clear description on how to dress the ID of the backplate taper to get it to fit the spindle better.