BTC Chuck

Bought a used 3 jaw chuck, and from looking in MSC catalog, it appears to be a BTC Zero-Set chuck. Their website seems to confirm this. Curiously, it only has one scroll socket. No backing plate with it. I have taken it apart, very well made and fit together. But, the 4 opposing "set" socket head screws are rusted solid to the body. I have soaked them with Kroil and Liquid Wrench for days and can't get them to budge. Any ideas how to loosen these? I'm about to resort to drilling them out, but would rather not. Additionally, MSC wants $183 bucks for a backing plate. That's about 4 times what I paid for the chuck. Can a universal backing plate be used (D-4)? Thanks for any help.

The typical set-true backplate has an o.d. the same as the chuck body and then a smaller o.d. section that projects into the chuck body, that the adjusting screws bear against. There are different styles, I only know about what I have seen.

The typical non-set-true backplate is a thin disk the same o.d. as the chuck. For a larger chuck (probably not found on a D-4) the backplate may be smaller than the chuck o.d. and may fit entirely within a recess in the chuck body.

For a typical D-4 chuck the non-set-true backplate might be 5/8" thick while the set-true might be 1-1/2" thick. So there is not enough meat to just make the latter out of the former.

I have successfully adapted two styles of non-set-true backplates to set-true chucks. For the first I started with an inexpensive non-set-true backplate for a much larger chuck, that had plenty of meat to turn down into a perfect set-true backplate. (From Meridian BTW, thanks Dave.)

For the second I started with a non-set-true backplate for a same-size chuck, and turned a 3/4" thick disk to fit the chuck recess. Then bored out a slight recess in the backplate to securely register the disk and bolted it to the backplate. So it is a two-piece backplate but it works fine.

I hope this is clear enough. If not, please ask...

The better chucks have only one scroll socket, to save you the trouble of marking and remembering to use the same one every time for consistency.

Bob

A few times I've had to use heat to remove a rusty bolt, not by the usual method of heating the casting, but by heating the bolt. This takes time, as continuous heating will soon melt the bolt head. You have to "pump" the heat down the bolt body to the rusted threads. The rust seems to be a pretty good insulator, helping to confine the heat where you want it. Use acetylene, not propane to reduce the time. Once the rust is hot enough, it seems to act like a lubricant because the bolt unscrews easily. Give the bolt head time to cool off before wrenching on it.

Toolbert, thanks for the idea of making a backing plate and adding the 'ring' on the inner portion to adjust against. I will certainly consider doing this if I can find a piece of stock to make it with.

Jim, I will try some heat to loosen up the screws. Don't know if I can heat it the way you describe, these are socket head screws and they are "internal" so to speak. Nothing is protruding through the body of the chuck to heat, both ends are within the threaded portion of the body. Bu some heat will tried.

Thanks.

Another handy way to heat bolts and other stubborn parts is to put as large a piece of copper rod in the rod holder of your electric welder put the rod solidly against the set screw or bolt and then have someone put the ground on the outside of the part. The rust acts as something of an insulator for heat and the set screw will get red hot in no time. I have used this to remove big snap rings that have one tang broken off. The heat anneals them to a soft condition and you can pull them out with vise grips. Be sure you have the copper rod on the part before you connect the ground so you don't spark up the threads and other tender parts. High current say 200 amps.

I deal with lots of rusted & stuck in place cap screws. I often place a bolt's head into the socket & TIG around it. Then I weld a nut to the protruding bolt threads & zap it off with an impact. I don't know if it is the heat from the welding or the impact power but I can't think of one I have not been able to remove by this method. I don't even wait for any cool down, just long enough to grab the tools & go.