Backing Plate

[dirty tools]

I just received a 4 jaw 8" used chuck ($65). Now I have to make a adaptor plate so I can use it on my 13" SB.

I am thinking of making it out of 4140 steel.
dimensions 6in. dia. by 3 in. long.

 

[Uglydog]

Please excuse my ignorance, why 4140?
Are you planning on hardening?
Is it more dimensionally stable than other less expensive options?

Daryl
MN

 

[Dan_S]

4140, is a pain in the butt to machine, specially when you are trying to hit a tight tolerance, and need to take small cuts. I'd recommend cast iron which is the standard back plate material. If you want to go with steel, id recommend something like 1144 stress-proof, or 12L15 if your shop environment is dry and not subject to drastic temperature swings.

 

[T Bredehoft]

Go with Cast Iron, its dirty working, but stable as you could wish and easily machined.

 

[joshua43214]

As the others have suggested, go with cast iron. There is no real substitute for it in this application.
Steel is a poor second choice.
Get a semi-machined or pre-threaded plate from Shars, or get a 1.5" thick piece of continuous cast from Ebay or Speedy Metals.

 

[kingmt01]

Will a 8" fit on your 13" swing? Carful running those jaws out to far.

 

[Bob Korves]

I think cast iron is also better at dampening vibration that can cause chatter.

 

[David VanNorman]

Cast is much better to work with . You can get threaded backing plates for not much money and you have a start.

 

[dirty tools]

the original 3 jaw chuck has a steel backing plate, that is why I was going with steel.
I know that most newer chucks use cast.
I am not sure of the type of material I should use.

 

[Dan_S]

Is the original chuck and adjustable one?