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Chuck back plate quality required?

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Birdpath

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#1
Hi guys:

I am in the process of setting up a 1340 lathe, about 10 years old and originally sold by MSC. It came with a three jaw 6" chuck. I just bought a Bison 8" independent four jaw chuck (new old stock), D1-4 mount. I am looking at back plates for this Bison chuck and see prices ranging from $87 to $488 depending on brand (e.g. Asian import vs Bison brand with Grizzly in between). Any suggestions on how imperative the price and assumed quality of a back plate is to the function and accuracy of the chuck?

I don't want to cheap out on the back plate having just purchased a nick chuck. Strictly home hobby use, but would love to buy once with no regrets.

Thanks, Daniel
 

Bob Korves

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#2
The best back plate is one that is made or finished in place on the lathe it will be used on and marked to index spindle to chuck for future mountings. That way it is by definition in perfect concentricity with your lathe when it is machined, if done correctly. The extra money for the high end mounts does not really matter in that case, most any mount will have adequate mounting to the spindle and good enough cast iron. The register may need to be tweaked for a perfect fit to your spindle taper, but that is also the same on all back plates. Unless someone else here knows something I do not and hopefully corrects me...
 

petertha

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#3
I bought a insurgent G chuck which came with partially machined D1-4 back plate. This was my first go at turning it in-situ to fit the chuck recess but it went well. Their D1-4 pins & nose angle fit my lathe spindle very well, I am totally satisfied with it. It was half the cost of Bison (here in Kanuckistan).

The thing to watch is the lip that you need to turn down does not stick out that far (just guessing 0.150-0.200" depending on the particular chuck) so you have to be careful measuring & machining here as its critical to nice chuck fit. A typical micrometer would have to be a big one & even so probably cannot get in that tight. I used a 0-12 vernier. So just be careful of no burr on the edge when measuring, or not too far back on the boss where the cutting tool nose radius would influence OD. Take your time. I think I got it within 0.002" & then worked it down slowly with abrasive until the chuck fit nice. It felt like a 4140-ish type material cutting.

BTW if you are also contemplating a D1-4 faceplate for this model of lathe, you can read about my fitting adventure.
http://www.hobby-machinist.com/threads/d1-4-slotted-faceplate.52482/#post-438366
 

Suzuki4evr

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#4
I just did a thread on making a chuck backplate for my 250mm bison 4jaw scroll chuck. Why don't you try making it yourself? It is precision work but rewarding. I made it out of cast iron. It's a lot cheaper than buying.
 

mikey

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#5
The best back plate is one that is made or finished in place on the lathe it will be used on and marked to index spindle to chuck for future mountings. That way it is by definition in perfect concentricity with your lathe when it is machined, if done correctly. The extra money for the high end mounts does not really matter in that case, most any mount will have adequate mounting to the spindle and good enough cast iron. The register may need to be tweaked for a perfect fit to your spindle taper, but that is also the same on all back plates. Unless someone else here knows something I do not and hopefully corrects me...
+1 to what Bob said. I have back plates from Grizzly (Chinese) and one really gorgeous one from insurgent U and aside from the finish, they are functionally the same. There is no difference in terms of how they fit the register on my lathe and the pins snug the same. The material is also presumably the same grade of cast iron. What is different is the appearance and machining of the plate - the insurgent U plate is very, very nicely done, but once the chuck is mounted you won't see a difference.
 
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