PDA

View Full Version : New Bison 5C chuck - couple questions



brunneng
09-24-2002, 11:45 PM
Hey all,

I just picked up a Bison 5C chuck and I need to machine the backplate for it. I have a couple questions for the more experienced at this since this will be the first time I've machined one.

Material: should I use a cast iron round, CR alloy (any flavor?), something else...

I was thinking of a couple ways to machine the backplate.

1. mount blank to 4-jaw or trued faceplate. Surface the blank. Center, drill and bore hole for stock passage. Machine recess to fit chuck. Mount 5C chuck on blank. Remove blank from 4-jaw.
Grab and true drill rod in 4-jaw on lathe. Mount 5C chuck on rod via collet. Surface other side of blank, true edge and cut recess to match lathe spindle.

2. Mount and true first surface of blank. Cut recess for spindle. Mount blank on spindle directly. True second surface. Cut second recess for chuck. Mount chuck.

I'm thinking that my machine isn't robust enough to handle spinning the 5C chuck so far from the headstock to do #1. It's a small asian I'm converting to CNC - one reason for chuck.

So any gotchas to watch out for?
Any tricks to get the TIR of the finished mounting as small as possible to keep the advantage of using the collets in the first place?

Thanks folks.

Gizmo
09-25-2002, 12:34 AM
Is it a threaded spindle? If so, does it spin all the way on or does it need opened up to major (spindle) diameter? If you gotta open it, keep this real close. Spin it on to final position, then machine in place. Again, when you machine the recess, sneak up on it and get it tight. Then the chuck will run pretty true. Spin it off and it will never be quite the same unless you keep your fits very close. Don't trust the 4 jaw unless you have trued the jaws, and even then it won't be as good as machining right on the spindle. You're gonna like the collet chuck!

brunneng
09-25-2002, 01:03 AM
Both the spindle and the chuck have recesses and bolt on. The spindle is a rabbeted edge and teh chuck back is bored out so if they were the same size they would fit as is.

SGW
09-25-2002, 08:42 AM
#2. Turn blank to fit spindle, mount on spindle, and turn the chuck register "in situ" to minimize potential error.

I'd use a disk of Dura-Bar cast iron, the regular-grade gray iron. It machines nicely.

rmatel
09-25-2002, 09:59 AM
brunneng,
I've done a few of these. IMHO, the 1st task is to fit the backplate to the spindle such that removing and remounting yields minimum reproducable runout. You can always fudge the mounting of the chuck to the plate 'cuz this junction wil be semi-permanent, but you'll save yourself a lot of time and grief if the mounting of the final assembly to the spindle is hassle free. Once you have the faceplate mounted well, you can then machine for the chuck.
Note that the chuck has a recess for which you should provide a tight but not press fit.
Bob

P.S. when you find the best fit ( least runout) mark the relationship of the plate to the spindle so you can mount it the same way every time.

[This message has been edited by rmatel (edited 09-25-2002).]

Thrud
09-26-2002, 01:26 AM
brunneng:

The others pretty well said it all.
Cast Iron is the best choice. Don't make it too thin - it needs some meat.

Machine for an accurate fit to your spindle first then machine it for a snug fit on the chuck (Hand pressure required to press it into place). Take the time to doa good fit on your spindle - this could be a good time to learn how to scrape.

It is sometimes easier to make an exact duplicate of your spindle first so that you can check your progress as you go.

Rustybolt
09-26-2002, 09:08 PM
I use one called a "Grand" imported by an outfit in Teterboro New Jersey. I think the Co. is called Grand also. There is no backplate persay. It comes already threaded for a SB spindle. It uses No. 21 Hardinge collets. The beauty of the thing is you can open and close the collet with the spindle turning.