Spindle thread adapters

[Dan Masshardt]

does anybody have experience with spindle adapters that go from one thread configuration to another for headstock accessories.

I have an offer for a collet chuck that might be cheap enough to buy the adapter and still be a good deal.

But I'm wondering if I'd be looking at more runout given the extra piece of the puzzle.

It seems like it would be no worse than an insert in a scroll chuck, but we want more precision out of collet chucks normally.

Thoughts?

 

[Fatdawg]

I used a spindle adapter on an old HF lathe when I first started turning years ago. I only used it with a scroll chuck at the time and had no issues that I can remember of.
It was a 3/4-16 to 1-8, I may still have it, what size do you need?

 

[KenV]

Dan - Typically you add a few thousands loss of precision when additional pieces are added to the hardware train.

Key is how much variation is in the system now and will the addition be acceptable.

Most of us use "budget" drill chucks on "budget" Morse Taper adapters. On a good day with careful installation we might get 5 thousands run-out. We could have purchased better quality and dropped the run-out but the price of precision goes up fast.

If you are using a metal lathe and headed towards precision the answer is probably different than if you are thinking of adding the adapter to a wood lathe that has lower expectation of precision.

Note that as with drill chucks, there are differences in costs and precision of adapters.

 

[monophoto]

I recently upgraded from a lathe with a 3/4-16 spindle to one with a 1-8 spindle. I didn't want to replace all of my accessories, so I thought long and hard about options. The drill chuck was easy - I could simply replace the arbor. And for the morse taper pen mandrel, the answer turned out to be a morse taper sleeve to allow an MT1 mandrel to mount in an MT2 spindle. But I had a bottle stopper mandrel that screwed onto the spindle of the smaller lathe, and when I priced out the options, it was less expensive to buy a spindle adapter than purchase a new mandrel.

So the issue is whether the additional gadget on the train increases the overall runout? Intuitively, one would almost expect there to be greater runout, and in my case, I did see a slight increase. But it wasn't enough to justify the greater expense of purchasing a new mandrel.

In general terms, I think the answer has to be 'it depends' - because there are really three factors involved:
1. The inherent runout in the accessory you are mounting on the lathe
2. The inherent runout in the adapter
3. Your tolerance for runout.

I have made bottle stopper mandrels using a bolt and a block of wood that I thread using a spindle tap. I use them for finishing - that way I can be finishing one stopper while turning another. The total runout of my original screwon mandrel when mounted on the spindle adapter is less than the total runout of my shop-made mandrel. So in my case, the answer was that the adapter was 'good enough'.

 

[tumbleweed676]

I have 2 lathes with different sizes of threads and use adaptors to go from to the other. Have minimal runout.