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Life's full of little (chuck) surprises!

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  • Life's full of little (chuck) surprises!

    I've had a bit of a 'chuck sorting' day today.

    The 12" 3-jaw that came with my DSG lathe is tired, to put it politely. I'd got a very nearly new PBI 3-jaw on a D1-11, a brand new D1-8 PB backplate turned up on ebay the other day so I grabbed it. It arrived today, so I loaded it onto the lathe spindle & clocked it both ways. The register was spot on, just a whisker of movement with the clock on the face so I took a fine skim off that. Bolt chuck on, put a 1.5" gudgeon (wrist) pin in the chuck & checked runout. 1 to 1.5 thou every time, taking it out & rechucking several times. Not too bad, probably about what I'd expect, it's not a super-precision chuck.

    I got a couple of grotty 3-jaw chucks in a sale last year, bought them cheap just for the D1-8 backplates which had no pins. Just finished making some pins, so cleaned up the backplate on this filthy heavy clunky Chinese 12" 3-jaw with what look like oversize reversible top jaws. I was just going to take the chuck off the backplate but thought what the hell, I'll, put a clock on it. Same gudgeon pin, same clock (.0005"), runout deflection was ZERO. No discernible deflection. Tried it again, rechucked it 3 or 4 times, same result. I could get half a thou by using a different station for the key.
    I know, it's probably chance & it'll be different another day or at different diameters, but I'll certainly play with it a bit more & run some more tests before it gets discarded. Actually might use it for the next job, got a 12" length of 7" round steel bar to machine & the big clunky jaws might be reassuring things to have