Boring Gingery Head Stock

The threading shouldn't effect the concentrically where it's important. What's important is the concentricity of the centerline of the spindle and the actual centerline of whatever is holding the part. On most lathes that would be the taper and the indexing surface for the chuck. I don't know what you intend to use for workholding, I don't remember what the original Gingery method was, a hole bored in the nose of the spindle, I think.
 
cjtoombs said:
The threading shouldn't effect the concentrically where it's important. What's important is the concentricity of the centerline of the spindle and the actual centerline of whatever is holding the part. On most lathes that would be the taper and the indexing surface for the chuck. I don't know what you intend to use for workholding, I don't remember what the original Gingery method was, a hole bored in the nose of the spindle, I think.
Click to expand...
The original gingery spindle was a .625 stub that would hold face plate with set screws but didnt seem very accurate so I took a long .750" bolt and made a spindle from that so I would have .750 threads instead of a .625 stub.
I have a 4" 3 jaw chuck that I made a chuck plate for with .750 internal threads to mount chuck.

Since I mounted the chuck I have been getting chatter occasionally, I assume it is from the extra weight hanging out and not big enough spindle for support.

I like the threaded spindle because I can cast almost anything with a threaded nut in the center and face it off, like face plates.

Since I spent alot of time on the lathe the last few days, I really have no run out on a 12" test bar when it is machined, I cant measure any anyway, so I think the accuracy should be ok for the new spindle..

Thanks for letting me know about the threading, is a bit of relief.
Thanks,
Tim
 
Factory threaded spindles have an unthreaded shoulder at the base of the threads that center the chuck, but It seams you are doing fine without that. All three jaw chucks have some runout anyway, as long as you do all your turning in one setup, it doesn't matter. Also, you can also mount a center then turn it so that it is perfectly concentric with the spindle before turning between centers. This is a fairly common practice and ensures concentrically. Of course, you have to re-turn the center every time you unmount and remount it in the machine. Looking forward to seeing how this turns :) out.
 
cjtoombs said:
Factory threaded spindles have an unthreaded shoulder at the base of the threads that center the chuck, but It seams you are doing fine without that. All three jaw chucks have some runout anyway, as long as you do all your turning in one setup, it doesn't matter. Also, you can also mount a center then turn it so that it is perfectly concentric with the spindle before turning between centers. This is a fairly common practice and ensures concentrically. Of course, you have to re-turn the center every time you unmount and remount it in the machine. Looking forward to seeing how this turns :) out.
Click to expand...
On that .750 bolt I made the spindle out of, I did machine a small relief at the shoulder and made sure of a flat area to register the chuck, I also made sure that the chuck had the same. When I cast the plate for the chuck, I just cast a .750 nut in the center and then machined the plate.
Took me some time to make that plate, like about 3 hours for the machining but took my time and wanted to make sure to get it right the first time, in the end I have .0015 runout, thats when I tighten the bearings up good to take out that play. Hopefully soon I wont have to worry about that anymore..
I have never had any schooling for machining, but I do the best I can, getting old and arthritic but its fun and cant sit still very long..
And thank for the tips about turning on centers.
Thanks,
Tim

Just about forgot to show some machining, I seen a different way to grind the tool bit and sure does a good job at .005 or less at one time.
View attachment 1015191726[1].mp4
 
Last edited:
Hi Again, been getting ready to machine this new spindle for the lathe.
Been getting things together for the boring for the new bearings, took some hard and long thinking of how to do it,
I'm pretty confident that it will work, and if it don't I'll be so embarrassed that nobody will ever hear from me again.:bawling:
Not really, but will fell very dissapointed, as I always do when screwing something up.

Now I have some questions about the bearings.
Ive talked to 4 or 5 different people and they all have different Ideas about how to install these bearings.

One says that I need 2 nuts, one before the bearing and one left hand nut after the last bearing to adjust pre-load..even though they are ball bearings. I think he don't know, miss-lead or whats going on, I thought that pre-load would be for bearings like used on a trailer, Race, Bearing, Washer, Seal, Nut to adjust pre-load...

I could go on and on about the other ideas but no need to, I have a way I think would work, besides this isn't some Hi production cnc lathe, its just for occasional use for me.

The first bearing will be flush with the bearing cap on the right side, then to the right of that will be a bronze thrust washer and then the machined shoulder of the spindle then the spindle threads..

To the left of that bearing will be a spacer, (the width of the cap is a little wider than
the 2 bearings by about .375) so that would be the width to bring that bearing flush on the left side.

Then to the left of that would be another thrust washer, thin machine washer and a lock collar, after that to the
left is pretty simple, pulley, new small bearing etc.

I was going to do all the machining here except the threading of the 1.125x12 thread..

So that's about it, If you think I'm wrong please tell me, don't wait till I'm done then tell me I screwed up like my
A.. H... brother would do..:face slap:

Thanks Again,
Tim
 
Did you get a double row angular contact bearing or single row? For a double row you probably don't need pre load so long as the bearing is constrained laterally on both the shaft and the housing. For single row bearings, they should take some pre-load. For single row you also need to be sure you install them in the right direction, or the pre-load and thrust will push the bearing apart.
 
Hi, the 2 bearings for the front are double row, and the one in the rear is a SKF heavy duty bearing.
The plan was (I always need a plan) was to not have to beat the bearing in but just some medium taps with the driver and hammer..
With your knowledge, which I really appreciate, that you could tell me what the bearing tolerance should be for the shaft and the bore.
Asked some friends of mine and its the same old thing, some say .005 for the shaft some say .003, and the same thing for the bore, so not sure who to believe.. was going to call the machine shop that will do the threading for me tomorrow, he's a 1 man shop and does really nice work and
always about 20-30% less than the big guys.

Well, one step at a time and everything will work out.

Thanks again for your help and the knowledge you bring to my project, I appreciate it.

Thanks,
Tim
 
.003 is way too much. For something like that you want a fairly tight sliding fit, so something like .001 to maybe .0015. Basically as small a tolerance as you can get and still slide it on, or more like push it on. Also, if you are using double row angular contact bearings, you only need one to take thrust in both directions. So you can put on in the front bearing, ensure it is held laterally in both the housing and on the shaft (you will need a nut on the shaft against it) and it will take the thrust. Then you can use a regular ball bearing in the back, as it will not need to take thrust.
 
Sorry, but getting confused, did you say I only need one bearing in front?
 
Yes, only one bearing is needed in the front. If you use a double angular contact bearing, it will take thrust loads in both directions as long as it is properly constrained. In that case you need one double angular contact bearing in the front fully constrained, and you need one plain roller bearing in the rear bearing constrained in the housing, not on the shaft. If you use single angular contact bearings you need one in front and one in back oriented so that they take the thrust load towards the headstock on the front bearing and away from the headstock on the rear bearing. So for instance, with your double angular contact bearing, it will have to be held solid in the housing by the outer shell with a nut or plate. The shaft will have to have the bearing trapped between the nose and a nut, both of which tighten against the inner bearing shell. The rear plain roller bearing will be held in the housing with either a nut or plate and be free to float on the shaft. That means the shaft will have to be stepped and the inner diameter of the plain rear bearing will have to be enough smaller to allow for the threads for the nut that holds the front bearing.
 
You must log in or register to reply here.
Back
Top