The Shop > Tools

Gingery Lathe Mods

(1/3) > >>

vtsteam:
Since I resurrected my Gingery lathe for my new tiny shop, I've noticed a fair bit more chatter than I remembered. I thought it was mainly related to the 3 jaw chuck spindle (I have different spindles for different purposes -- the faceplate has its own spindle, the 3-jaw has one, and I also have a milling spindle).

I first thought that the 3-jaw's relatively long overhang and greater mass was the main cause. But I think it's also wear in the bearings. These are split oilite bronze bushings, and while you can take up vertical wear by removing a shim, horizontal wear can't be reduced that way. And I think that might be the culprit. I can replace the bushings for a couple dollars, it's no big deal. but..........

Maybe it's time to up the spindle diameter, too, not just replace the bushings. This is a familiar job with this lathe. I call it "spindle creep" -- the Gingery lathe was originally built as desiged with a 5/8" diameter spindle. That was pretty flexible and chatter frequently a problem working ferrous materials if not turned between centers,  so I decided to increase the spindle front bearing to 3/4" a few months after I built it.

At first, because the cone pulley was 5/8" bore, I only increased the front bearing spindle diameter, not the rear. That meant the old pulley could still be used. The main reason I didn't do both was that I couldn't find a commercial cone pulley to fit. But I kept looking. Eventually  found a source for 3/4" bore cone pulley pair that had the right ratios and traded up to a full 3/4" spindle and bearings. I bought the 3 jaw chuck too. It worked but was somewhat of a disappointment even with the larger spindle since I would get chatter in cutting steel with even a 2" long workpiece.

So now that the bearings need replacing I'm thinking It's time to move up to a 1inch diameter spindle. That would allow a hollow one as well with a 3/4" bore, and probably an internal morse taper up front. The combination would increase the usefulness of the lathe quite a bit.

The only difficulty is the Vee belt cone pulleys again. If I choose the same ratios, it's not possible actually because there would be no meat for the smallest sheave -- I think that's probably 1-1/2" diameter, and the 1" bore would probably cut through inside the Vee. Also I couldn't just increase the size of the whole cone, because the biggest sheave now just clears the headstock base.

But tonight it ocurred to me that a flat belt, or maybe a poly Vee belt would work -- it's much shallower. And better actually. I'd have to make the cone set myself, but that shouldn't be a problem.

So tonight I sent for a 300 j6 poly-vee belt from Ebay to have something to check out against the rig. We'll see if we can make the space to fit it. If so, I think I'll go ahead with the new 1" spindle size. That would really improve the lathe in many ways.

If successful, I have a few other ideas for improvements, including possibly a new leadscrew, and maybe using timing belts on the leadscrew drive to provide screw cutting capability, which my lathe lacks now.

But lI want to look at the spindle enlargement first....

vtsteam:
Hmm, one more thought -- If I did the same thing again -- larger front bearing than rear, the nose end could maybe be 1-1/4" while keeping the 1" diameter aft to suit the polly vee pulley. I still couldn't get away with more than a 3/4" hollow in the spindle, but could probably accomodate a larger morse taper in the nose. and probably do an ER collet system, too. I'll have to check things out on the machine to see if this is possible for the headstock at the front end.

awemawson:
Off the wall thought Steve ... Could you make the spindle large  enough to cut the Vee pulley shape in the rear end?

Kjelle:
Interersting... Will follow this!

 :worthless:

Kjelle

Eugene:
Steve,

Looking at the Gingery lathe drawings there doesn't seem to be any much provision for eliminating or avoiding spindle end float. Could some of the problem with chatter come from that direction? A recent exercise in finding and eliminating chatter on a small lathe eventually led me to end float; a cheap thrust bearing later and it's cured.

Eug

Navigation

[0] Message Index

[#] Next page