[How-To] Front mount chuck

[Danshell]

I am buying a 6” 4 jaw independent chuck fir my SB10k and it appears to be bolted on from the front of the chuck.

I have mounted a rear mounted chuck to a backing plate as that was easy. I was able to slightly oversize the holes in the backing plate to make sure the bolts went into the thread on the chuck.

However I am a bit concerned the holes in the chuck on the front mount won’t be as forgiving.

Is it as easy as using a transfer punch through the chuck to mark the backing plate for drilling and tapping?

Thanks for any advice

 

[mikey]

It's a simple, basic job that you can easily handle. Don't worry, you got this.

You need to turn the snout of your back plate to fit the female recess in back of the chuck. If you make this a light press fit (0.0005 - 0.001") the chuck will register automatically. Just make sure the projection of the snout is shorter than the recess is deep so it doesn't bottom out. If you do the above and the fit is slightly loose (stuff happens) then try to get a shim in there to center the chuck on the back plate before marking the holes for drilling.

While getting the chuck centered precisely on the back plate is not that critical on a 4 jaw it does impact on balance so try to get it centered accurately. Then use a close fitting transfer punch and mark ONE hole; doesn't matter which one. Before you remove the chuck from the plate, make a Sharpie mark across the rim of the back plate and the chuck so you can use them to precisely realign the chuck on the plate later. Now remove the chuck and drill/tap the back plate for that one screw. Reassemble the chuck and align the marks you made on the chuck and plate, then tighten that one mounting screw firmly. Those marks will allow the screw to orient pretty much in the center of the hole in the chuck through which it passes and the screw will hold everything together solidly so nothing shifts as you transfer the other three holes to the back plate. Now remove the chuck and drill/tap the other three holes and you're done.

Most higher end chucks mount like this, from the front, but the general process is the same for all of them even if the screws come from the rear. Trust me; marking the chuck and plate and installing that one screw makes a difference in the accuracy of your other punch marks. I would do it.

 

[Danshell]

Thanks very much Mikey I appreciate the advice.

I managed to finally find a youtube video last night of a gent who did it exactly as you described, and it was also on a Southbend, albeit a 9 I think.

 

[mikey]

None of this is hard. Just work carefully and things will go well.

 

[Danshell]

So both my chuck and the backing plate have arrived.

I bought a pre threaded blank backing plate to suit my lathe. I just put it on the lathe (the backing plate) and it has a massive amount of run out. I am talking millimetres, not fractions of millimetres.

So being new at all this I can only guess that Ill need to machine this thing true before I put the boss in place to suit the chuck?

Will machining the front and outer edge be enough or will I need to also skim the back?