WTK: Any problem with using a Spindle adapter?

[mark hettinga]

I’ve a Vega lathe with 1”x8tpi. I’m considering the Nova Titan chuck as there are a lot of accessory jaws for it. I’d like to turn up to 24” stuff outboard. Other then the obvious it’s hard on the bearings comments, bearings can be replaced after all, are there any other negatives I should be considering?

[John K Jordan]

I’ve a Vega lathe with 1”x8tpi. I’m considering the Nova Titan chuck as there are a lot of accessory jaws for it. I’d like to turn up to 24” stuff outboard. Other then the obvious it’s hard on the bearings comments, bearings can be replaced after all, are there any other negatives I should be considering?

I think the Nova Titan is direct threaded only - mine is 1-1/4x8tpi. With a quick search I can't see that it comes in any other threads but M33. I suspect the reasoning for this is it is intended to be used on larger lathes.

I'd be wary about using a typical adapter which extends the chuck several inches from the lathe spindle. Unless the precision of the adapter is perfect it can cause some wobble which isn't really a problem turning one surface but could be when reversing a bowl to do the other side.

But what would worry me more is the stress a huge blank could put on the adapter and your lathe spindle, not as much a problem with a larger lathe with a heftier spindle. I'm imagining a possibility of bending/damaging the spindle itself as well as the bearings. If there was an insert version of the Titan for 1x8tpi that would keep the mass and forces closer to the headstock.

I do know a guy who turned fairly large bowls outboard on a lathe with a small spindle but instead of a big chuck on an adapter he turned with a face plate threaded for his lathe which would be stronger. He still had to bolt the lathe to the walls to control the vibration.

But if my long-term goal was to turn big I might start saving up for a larger lathe, especially so I could use tailstock support which would be important to me. Might find a used one - a elderly friend hinted his big Stubby was way too much for him now and maybe I would like it. However, my PM3520b is big enough for me.

Or what about building a custom lathe? That's what Lissi Oland used for really big bowls!! https://www.youtube.com/watch?v=1PMEJ7rirso She told me she always uses a big faceplate for large work.

JKJ

[Brice Rogers]

Agreeing with and adding to what John said, it might depend on the weight and geometry of what you're turning.

If you intend to turn large platters, the weight won't be excessive and the center of gravity of the platter will be fairly close to the spindle. But if you're planning on mounting a large heavy log to make a 24 inch diameter vase or bowl, say, 12 inches long, the center of gravity will extend by about 6 inches, putting a fair amount of stress on the spindle.

I suppose that you could reduce the stress on the spindle by using a live center whenever possible and if you have something large with an aspect ratio (length to width) of over 1:1, then also use a steady rest at the point where you need to remove the live center.

I ended up getting a 25" slab of beautiful magnolia wood and was considering making a huge platter. But the more I thought about it, what the heck use would we have for a platter that large. I ended up making a 17 or 18" platter that will still be at the upper end of what we would use. I suppose that if were making a piece of art to hang on a wall that 24" would still be reasonable. But not for a utility piece.

[Brice Rogers]

BTW, I have a Grizzly G0766 with a 1-1/4 x 8 spindle. It has a 22" capacity. I found a 5" Grizzly chuck kit for a 1 x 8 chuck that included Cole jaws, 2" jaws, 5" jaws, pen jaws, step jaws, screw drive, etc. for less than I would pay for a larger 1-1/4 x 8 chuck with only a single set of jaws. So I bought a $10 adapter and a couple of chucks. The runout on the adapter is so small that it is not an issue.

So, in my case I downsized from a 1-1/4" spindle to a 1" chuck (the opposite direction that I think Mark was contemplating. I don't have any reservations of turning up to a 22" platter (other than questioning the practicality of a platter that large). But I doubt that I'll ever turn a 100 pound chunk of wood.

[John K Jordan]

...
I suppose that you could reduce the stress on the spindle by using a live center whenever possible and if you have something large with an aspect ratio (length to width) of over 1:1, then also use a steady rest at the point where you need to remove the live center.
...

I understood Mark wanted to turn the largest pieces outboard. Mounted away from the bed wouldn't allow either a tailstock/live center or a typical steady rest when it could be most useful.

[Brice Rogers]

Good point, John. I hope that Mark doesn't hurt himself.