4-jaw chuck question

Hello all,
First, 3-jaw (lathe/mill) chucks: are they all self-centering, or do
some have a way to separately control the jaws? Is there any jargon
that distinguishes them?
Now for the real question. Assuming (which I suspect would be the case)
that I cannot use a 3-jaw chuck, consider a ring with some holes drilled
axially through the ring. One approach is to (on my mill) square a
block of the desired thickness, drill the axial holes, bore the center
hole, and then go find a lathe, or attach a chuck to my rotary table to
mill the OD. Actually, the chuck might not have reason to leave the RT
for this job, but that's just details.
In either scenario, is there any trick to sweeping the bored hole to
align the chuck? The part would be held using the bored hole, so I am
concerned about the indicator colliding with the jaws. Is it as simple
as grabbing with just the top/end of the jaws? Are there commonly used
spacers analogous to parallels for a vise?
The rings are thin enough to be a challenge to clamp. My first thought
was to drill through them and tap holes in a sub-plate, but there is not
enough room for substantial screws. I managed to make a plate that
appears to work, but it seems likely that something will shift or I will
strip the threads.
I know there are probably better way to do the job, but I am trying to
minimize the time I would need on other people's machines. I also am
"refusing" to rush my lathe purchase. You guys gave me some excellent
points to check, and I plan to work through that to get a machine I will
enjoy. BTW, another call to Enco suggests that they can indeed provide
a lift-gate for a 1000 lb lathe. From the ground, I could hoist it into
my truck, go the 50 ft downhill to the garage, back the truck into the
garage, and then hoist the lathe to its new home. Not under pressure
Reply to
Bill Schwab
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If you already have the mill then how about this:-
1) clamp the squares on the rotary table and mill out the bores.
2) clamp a flat piece of scrap larger than the rings (steel, ali, MDF, plywood) on the rotary table and mill a flat surface the same OD as the ring bore and a bit less tall than the ring height, sort of flat top hat shaped.
3) screw another piece of scrap onto this, siting the screws asymmetrically so that it'll only fit one way. Use as many screws as will be needed for even clamping. Mill that so that its OD is marginally less than the OD that the rings need.
4) you now have a jig that can be used to clamp the part formed rings onto the rotary table so that you can mill the OD of the rings. No holes needed. If the holes are part of the design, then drill them through the scrap and the ring at this point.
Mark Rand RTFM
Reply to
Mark Rand

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