The Shop > Metal Stuff

Casting a Lathe Chuck Backing Plate

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vtsteam:
I need a 4 jaw chuck for my new lathe to work on the Rider engine I'm building. I got the chuck from Shars, but it needed a backing plate. I did consider just bolting it to my faceplate, as I do with my 3-jaw. But unfortunately the faceplate has a six slot pattern, and the new chuck has a 4 bolt pattern.

The faceplate is not easily milled for another set of slots without a carbide mill, and I really don't like this faceplate much anyway. I'll probably make a new one some day.So I decided instead to make more conventional backing plate for the 4-jaw -- I'm thinking it may be my main go-to chuck anyway, in future.

So I band-sawed out a simple 6-3/4" disk out of 3/4" plywood for a pattern, rammed it up in greensand, and did a little larger melt than I had before in my A6 crucible. The iron is from a brake disk -- about 11 pounds was melted, and I added .35% ferrosilicon. The furnace had been fairly extensively patched, and completely re-coated in ITC 100HTceramic coating.

For some reason the furnace took much longer to melt that iron, about 50 minutes compared to 20 in the prior 3 runs. I was using off road diesel instead of regular diesel. It seems to have different characteristics, and I'm wondering if the furnace damage as well as slow melting is a result of the recent change. I will probably switch back to regular diesel -- particularly here in winter temperatures, when viscosity is heavier for these light oils.

Everything did eventually melt -- I did have to add iron as the melt progressed to fit it all into the A6. But when I went to pour, the crucible again stuck to the firebrick plinth. I had put cardboard under it, but I think the longer melt and fuller crucible resulted in slag dripping down the outside to weld the crucible to the plinth.

This discovery right at the pour meant I couldn't easily get the ring shank onto the crucible -- the firebrick was too large to set it in the ring. But because the shank I'm using now is expandable I was able to stretch it down over the top of the crucible, and pour that way.

\Unfortunately in the excitement of trying to get the crucible situated in a shank in time to keep it hot, I wasn't able to do as good a job slagging just before pouring it. I had slagged once while it was in the furnace, however.

Anyway the pour was accomplished, and the crucible returned to the furnace to cool down slowly.

I had put a big riser in the center. The sprue showed pieces of slag, the riser looked clean, and shrinkage was very apparent as it cooled.

vtsteam:
And, here is the break out. I was pretty well pleased with the casting, considering the pattern making was about a 10 minute afterthought on a day I hadn't actually planned to cast on....., and the problems I had with the crucible sticking when I did.

vtsteam:
And here it is being machined on the new lathe's faceplate, which it will eventually replace. To clamp it, I simply drill two holes in the plate, tapped them, and bolted it in place.

RussellT:
The casting looks good from the machining.  Well done.

Russell

PS Yes, I remember the engines well,  I still have mine here.

vintageandclassicrepairs:
 :clap: :clap: :clap:

John

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