chuck jaws

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tornitore45
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Location: USA Texas, Austin

Re: chuck jaws

Post by tornitore45 » Tue Feb 05, 2019 2:35 pm

Backplates are available in many popular treads but they cost almost as much as a chuck.
Mauro Gaetano
in Austin TX

spro
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Re: chuck jaws

Post by spro » Tue Feb 05, 2019 7:15 pm

I need to go back to where the OP said 1 3/8" x 8. The 9" South Bends are 1 1/2" x 8 tpi unless it is a very early model. We don't have much info about what type it is. New and used back plates, threaded 1 1/2" x 8 can be found on the bay or whatever market you found chucks. My 9A has the newer bearings but wouldn't feel comfortable hanging a heavy 6" + chuck on it. 5" is good and precision Emco even better.
While on the bay, I noticed the collet chucks are reasonable. item # 352328461653 has a good tutorial about checking your lathe spindle before even getting into the collet chuck. The thing is that the S. B. 9" had provision for 3C collets which fit tight thru adapter but they were only 1/2" max capacity. Morse taper #3 has larger capacity but the taper locks tight and requires a certain way, besides hammering, to release.

spro
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Re: chuck jaws

Post by spro » Tue Feb 05, 2019 7:25 pm

5C collets are everywhere but I didn't realize ER 40 became this affordable. So a fully finished back plate 1 1/2" x 8 with an ER40 collet chuck is only 147. + 22. s/h. Interesting. The size is 5" and considerably less weight than a full chuck. The "stick out" is about the same and round capacity 1 1/8" .

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SteveM
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Re: chuck jaws

Post by SteveM » Wed Feb 06, 2019 8:39 am

Best deal on a 1-1/2x8 backplate is from littlemachineshop.com

Steve

earlgo
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Re: chuck jaws

Post by earlgo » Wed Feb 06, 2019 10:31 am

When I went through this with the 12" Atlas I bought a backplate from SHAR with the chuck. The backplate did not fit properly and so it got into a major repair/rebuild of the chuck plate. I bored out the center and threaded it with a 20pitch thread. Then I cut a bushing that would mate and secured it in place with Loctite.
DSC01074 (640x480).jpg
Bushing in place
Then I cut the threads almost complete on the lathe and then finished them with a 1_1/2-8 H5 tap that I found on e-bay.
Back plate tapping.JPG
Back Plate Tapping
It came out OK but I still had to fit the pilot on the spindle and then adjust the centering pilot so it would all run concentric.
DSC01093 (640x480).jpg
adjusting the pilot
This was done by drilling and inserting 6 pins and then turning the diameter across the pins to fit the back of the chuck. Big pain, all of it.
Other posters have a less labor intensive solution. Be advised. :shock:
--earlgo
Before you do anything, you must do something else first. - Washington's principle.

Lewayne
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Joined: Sun Feb 03, 2019 4:02 pm

Re: chuck jaws

Post by Lewayne » Wed Feb 06, 2019 12:09 pm

sorry guys, I'm way to new too this stuff. Indeed the threaded shaft on the head stock is 1 1/2" with 8 threads. (I thought I had measure it at 1 3/8)???
In inspecting the old backer I determined it to be very unsafe. Hardly any metal holding it on. Could snap off at any time. But that looked like too large a project for both me and the machine, making a new one myself. I found a backer the right size at Victor tool. Is expensive though. about $140 with shipping.
Do you guys think those chucks are indeed too heavy for my 9" 1938 SB lathe? model C If I remember right, uses the gear set for threading. I suppose I could sell the larger one, now that it is all cleaned up, and get a 5" ? what size was originally on a 9" lathe?

Mr Ron
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Re: chuck jaws

Post by Mr Ron » Wed Feb 06, 2019 12:31 pm

There are reasonably priced plates here. https://www.wttool.com/index/page/categ ... _id/16516/
Mr.Ron from South Mississippi

spro
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Re: chuck jaws

Post by spro » Wed Feb 06, 2019 2:56 pm

Reasonable for new, these days. Most likely, any good flea market or tractor show with vendors have some machinery parts. 1 1/2" x 8 is very common size. You will have to inspect the internal threads and condition because there is worn out junk. There may be another Reason why that back plate is apart. Altogether; doing internal boring and threading, isn't the first thing you need now.

spro
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Re: chuck jaws

Post by spro » Wed Feb 06, 2019 3:06 pm

5" chuck is reasonable for the 9" . The old ones are heavy enough.

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SteveM
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Re: chuck jaws

Post by SteveM » Wed Feb 06, 2019 9:40 pm

This is the one I got:
https://littlemachineshop.com/products/ ... &category=

$45 (it was $30 when I got it, but that was 12 years ago).

You can read about my backplate machining adventure here:
viewtopic.php?f=42&t=76302&p=95928
viewtopic.php?f=42&t=76335&p=96163
viewtopic.php?f=42&t=76527&p=97582

Steve

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