Gingery Lathe Mods

[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!

 

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

[chipenter]

My Faircut lathe had a replacement spindle 1 1\4" dia with a mt3 taper and bored to 3\4" , chatter was always a problem and I bent it on a dig in , made a new one mt2 bored to 5\8" mutch better , my SouthBend has mt3 and bored to 3\4 and is 1 3\4" , at 1" I would leave it solid may be make a seperate collet spindle as well .

[vtsteam]

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

YGood thought. You might be able to Andrew, and I actually thought about that before the poly-vee idea, but the disadvantages I realized are that I would have to machine the small pulleys and their sheaves for each of my spindles. And the spindles would no longer slide through the bearings for changing them. I'd have to remove the bearing caps because the sheaves would be bigger than the bore.  Right now I just loosen the cone set screw and the collar at the back of the headstoc setscrew and slide the whole spindle out to change.

[vtsteam]

Eugene, maybe, I'm not sure about end float. On as simple a lathe as this, there is just a bronze washer type thrust bearing on the nose end, and the collar with a setscrew at the back of the spindle to keep things in place. You just push in the spindle and lock the back collar by pressing it tightly against the headstock. In other words, It's all done by hand, and you eliminate play by holding things tight while tightening.

[vtsteam]

Chipenter, that's a definite concern, then. I do really want a hollow spindle this time around, but it doesn't have to be 3/4" if that seems too much.

This would also argue for the 1-1/4" spindle nose vs. 1" throughout.

MT2 would be okay, and I have MT2 collets already for the old Atlas hrizontal mill (I think they're MT2 -- have to check), so MT3 wouldn't be a necessity.

[vtsteam]

Further thoughts:

3/4" U.S. water pipe is about .822" ID and 1.050" OD.
1"    U.S. water  pipe is about 1.045" ID and 1.315" OD

So if I brazed a short bit of 1" pipe over an arbor of 3/4" pipe, I could turn the nose section 1.25" OD and probably just ream out the rear bushing to suit whatever the 1.050 aft spindle O.D. becomes when trued.

This would give me a wall thickness of about .214" at the front bearing and a .822 bore. throughout.

If worrisome at that (or to suit my MT2 taper tooling) I could always plug the nose end, and bore smaller, if desired. But I don't think it will be a problem.  This is a 7" lathe without backgear, and driven by a 1/4 hp motor. If I bend a spindle, I'll just make a stronger one.

[vtsteam]

Tricky part is going to be boring the headstock to fit new bearings. There's a sequence you go through to bore it originally on a Gingery lathe, but it's not exactly reversible because you remove your reference boring jig when done.

The actual bore location is not critical to start with as long as the bore is parallel to the ways. But once the lathe is built, and the tailstock made, the bore location is determined -- at least in the vertical dimension. The tailstock can be set over horizontally, but the height is fixed.

Not impossible of course, but will take a little thought about procedure to maintain alignment.

[vtsteam]

Sorry Kjelle no pics yet because nothing is being made so far, just thinkg things over, but pics will come, promise!

I found some really nice heavy duty oilite bushings 1" ID that I had left over from a job. These are the silver kind, not the sintered bronze. I pulled the caps off of the headstock and checked how they might fit.

Looks like the 1" bushings could just be made to fit if I bored the headstock. Unfotunately, any larger would hit the cap hold-down screws. I suppose these could be moved, but that would be a much bigger project.
So I'm dropping 1-1/4" nose side bushing idea. I think I'll go with the full 1" spindle for the time being.

I noticed that I had the cap screws somewhat offset compared to the spindle centerline. The spindle is about 1/8" closer to one set of screws. I'll need to adjust that by boring along the mid distance between them if I'm to fit the bushings between them. That will offset the spindle in relation to the tailstock, but the tailstock set-over can be adjusted to compensate in the horizontal plane.

To get something done today, I cut some 3/4" pipe for spindles and measured the diameters.They are about 50 thou too large for the bearings. Rather than thin the spindle walls too much, or ream the bearings too thin, I think what I will do is shoot for a spindle diameter of 1.032, and ream the bearings to that. That should take minimal material off of the spindle, and only a 64th off the wall thickness of the bearings.

I also took apart the tailstock, to check if it was suitable for holding a bar to bore the head with. That would solve the boring position problem. Looks do-able. I'd set the tailstock over before boring the head, to center the bore between the cap bolts, as mentioned already. The new position of the tailstock would be the new center.

So, I think it's settled then - 1.032" spindle and bushings, and bore the headstock from the tailstock after setting over about 1/8th. Use heavy duty bushings I have onhand..

[vtsteam]

I've been waiting for the new belt to arrive before doing any work on the lathe. If I bore the headstock, I want to have everything ready to reinstall the new spindle(s) or I won't have a working lathe in the tiny shop.

So I've been working on the new cone pulleys. Here's a pattern and a baked sand core:

[Will_D]

In the course of tidying up the shop for the new mini-mill I remembered/found my old Centec 2 horizontal mill.

Some time ago I did a basic refurb that involved replacing the CI Pulleys (A section V-belt) and the like ( 3 step) with a more useful 4 stage pulley and a 2 step on the motor. Rather than cast the pulleys I made them from MDF.

[The original 4 step geometric speed pulley design came from Tameside Tech College Toolroom teacher who lent me the patterns and then we cast a pair for my drilling machine] Those were the good old days when a Tech college had an "In House Foundry" plus more big machines to play on. (They also had a rolling road in the car/motor vehicles bit of the college but thats another story)

Anyways BOT:

These were tuned to size and profiled with a Z section HSS form tool and mounted on some metal bits with some long screws plus lots of PVA glue. [Vague I know but it was a long time ago]

The pulleys were then soaked in diluted Polyurethane varnish and after that had dried more neat PU. The slight roughness of the MDF and the PU gives agreat "Bite" on the belt.

Some photos:







I really think that for this level of belt drive why cast aluminium?

Will

[vtsteam]

Hi Will your pulleys look great, and I'm sure they work as well! 

Personally I greatly enjoy casting aluminum and truly dislike working with MDF, but that's just a prejudice on my part. I don't make patterns from MDF either. That doesn't mean I don't greatly admire your finished pulleys, I do! 

A few more (admittedly arguable) reasons I'll be casting -- I only have to make one pattern for the two pulleys I need (and however more I want in the future), I don't have to add metal hubs as you did (and so make and connect two parts for each pulley) , and I'm making 6 groove poly-vee belt pulleys, not standard vee belt types, I think the fit will be better. And aluminum castings fit my lathe style. Plus I have an excuse for setting up a casting capability in the tiny shop!

I might make a Potts spindle at some point, and then I would probably make wooden pulleys for the traditional fun of it, though likely cherry or other hardwood -- as I have lots of that from my sawmill.