Need an adapter to mount a 4 jaw chuck to a Seneca Falls Spindle

[PHPaul]

Long, long story, but my search for a 4 jaw chuck for my Seneca Falls Star 30 hasn't met with any success, so I grabbed a 4 jaw that will work if I can get an adapter made.

I can do up a dimensioned drawing if anyone is willing to take this on (for pay, of course) but the basics are as follows:

Lathe spindle is 1-9/16ths by 10TPI, with about a half-inch of threads.

These are just quick-and-dirty rough measurements: "Socket" on back of chuck is 3.92x, 4 holes on 2.94x circle.

I suspect the best approach would be to turn the major diameter slightly oversize and I'll turn it down to fit when I get it.

If someone is willing to take this on, I'll do my best to get more accurate dimensions and provide a detailed drawing.

 

[pdentrem]

Do you have a face plate or a 3 jaw chuck large enough to turn the piece?
I would thread the backing plate first thing so that it fits your spindle. Either by making a gauge or thread to dimension. Then face the surface that will contact the spindle, install on the said spindle and finish.
Pierre

 

[PHPaul]

I do. What I don't have is enough experience to get the threads right and everything square, plumb and flat to minimize runout.

I suppose I could try it, the worst that would happen is that I'd turn a bunch of steel into waste and chips. Wouldn't be the first time...

 

[pdentrem]

Understood.
Practice making the threads first on the exterior of 1 1/2” ABS pipe. Once you feel comfortable with that, next move to cutting the threads on the interior.
I made a plug gauge that is a replica of my spindle first. Here is my post on making 2 plates using semi finished plates.
Pierre

Making a couple of threaded spindle backing plates for my lathe

When I sold my Atlas 10F24, I held on to my Bison 5” 3J, as it was fairly new. Naturally I needed to make a new backing plate to mount it onto the new lathe. The old plate was 1 1/2” X 8 while the new spindle is 2 1/4” X 8, so I needed new metal to do this. I recently purchased 2 backing plates...

www.hobby-machinist.com

 

[PHPaul]

It just occurred to me that I have a small faceplate that fits my spindle. I don't foresee needing it (I have a larger one if I ever need a face plate) and it would be a relatively simple task to turn it down to use on the chuck.

I did read your thread and got a good tip on the "transfer screws" which is a great relief as I was really worried about positioning the mounting holes accurately.

I believe I will take a shot at this myself. Thanks for the link!

 

[benmychree]

Not good to use steel for backplates, it may gall against the steel spindle, use cast iron, you may be able to find a semi finished casting or a rough casting. Best to make a plug gage of your spindle thread, exact as possible to the pitch diameter measured by 3 wire method or thread micrometer. I have made them for all the lathes that I have owned, except a 30" American with acme threaded spindle, it already came with chucks.

 

[matthewsx]

I used a tap to cut the threads in mine.

 

[benmychree]

I used a tap to cut the threads in mine.

Not a common size tap, and also taps are not known for starting in straight, unless possibly roughed out nearly to size and finished with the tap.

 

[matthewsx]

I found mine on eBay for short money, actually had a local machine shop do the job since I didn't have much confidence. Worked out fine for me but the backing plate was already cut for the chuck and all I needed were bigger threads.

I do have a couple of rusty chucks I'm trying to bring back into service so maybe I'll try single pointing their backplates after boring to size.

John

 

[projectnut]

I've made several backplates for various chucks to fit on my Seneca Falls #20 lathe. If you have a used equipment store in your area you should be able to find one from another lathe to use as a material source. In our area the equipment dealers were all but giving them away. Most of those I bought were $20.00 and under. Depending on the size of the one you find you can either bore it out and rethread it, or if the ID is already larger than what you need bore it enough to remove the threads and make a home made bushing a few thousandths over the final bored size and press it in. Secure the bushing with a couple pins then bore and thread it to the proper size.

I made a plug with the proper size threads (in my case 1-7/16-12) and used it as a gauge when cutting the internal threads. Once I finished that part I screwed the new backplate on the spindle and turned down the OD to the size to fit the new chuck. The final step was to secure the backplate to the new chuck. In cases where the chuck had through holes I fit the backplate in place, lightly clamped it and used a transfer punch through the chuck face to mark the location of the holes.

In cases where there were already holes in the backplate, but no holes in the chuck that would align with them I used the transfer punch through the backplate to mark the location for holes in the back of the chuck. Just be sure you align the parts so that you don't interfere with the existing jaws or screw mechanisms. Then it's just a matter of tapping the threads to the desired size and fitting the parts together.

If you're doing it on your Seneca Falls machine be sure to select the proper change gears. One time I put the gear set on for an 11 1/2 tpi pitch rather than a 12 tpi pitch. I stood there scratching my head for quite some time wondering why the plug wouldn't fit in the threaded hole. When I finally realized what I'd done I had to remove the bushing, make a new one and thread it to the proper size. I had no idea where an 11 1/2 tpi pitch was used until about a year ago when I needed to make an adaptor to put antifreeze in one of the pressure washers. That's when I found out it's the standard size for a garden hose fitting.