How should I make this?



A llllllll llllllll B lllllllllllllllllllllllllllllllllllllllllllllllll llll llll D llll C llll llll lllllllllllllllllllllllllllllllllllllllllllllllll llllllll llllllll
Whilst I like Dave Bakers option it seems to ignore bore "C"
I would
Buy cut blanks at 47 long Chuck in the "A" area as little as you are comfortable with Rough allparts at "B" and "C" within .5mm of finished OD and ID Turn around, chuck on "B" and complete roughing of "B". Rough out Bore "D". Rough diameter "A". Mark jaw 0 on part to allow putting back up with minimum error. Do all parts Finish bore "D" end face and diameter "A". Main problem now is holding to finish "B" and "C" Make a mandrel as follows
R S T U
111111111111111111111111 111 1111111111111 1 1 1 11 1 1 1 1 1 Drill 10 1 1 1 Tap 10 1 1 1 11 1 1 111111111111 1 1 1 1111111111111111111111111 111
The "R" diameter and length is to allow chucking. "S" will be a slip fit in bore "D". A thick "O" ring will sit on diameter "T" and be compressed with washer "U" clamped up with a piece of 10mm studding through the spindle.
The parts previously roughed and part finished can now be loaded to the mandrel with the "A" face on the chuck jaws and finished on "B" and "C".
Some may say too much picking up and putting down, but the above tends to differentiate between roughing and finishing and the associated tool changes.
Thats what I would do, but I have "all the time in the world". <G>
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Richard

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On Sun, 30 Mar 2008 05:34:47 +0100, Richard Edwards
Oops. Just looked at my post, mandrel should really look like this - (View in fixed font)
R S T U
111111111111111111111111111111111111 111 1 1 1 11 1 1 1 1 1 Drill 10 1 1 1 Tap 10 1 1 1 11 1 1 1 1 1 111111111111111111111111111111111111 111
--
Richard

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wrote:

The part is described as a "top hat" so one would assume it doesn't have a bore C and isn't meant to be viewed in fixed font.
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Dave Baker
Puma Race Engines
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wrote:

There you go, my error. I must admit I always assume ASCI art is based upon fixed pitch font, and my reader is setup this way because of problems in the past, however incorrect in this case.
I therefore like your option even more! <G> The "O" ring option that I described is useful though. ;-)
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Richard

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Use a Fixed Steady to hold the 50mm diameter stock.
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Nourish
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Ian wrote:

Here's a really simple design for an expanding mandrel. You will need a suitably sized socket head cap screw and a nice long socket key - one that will reach the mandrel from the outside end of the headstock spindle. A piece of hex-rod and a spanner would do the job. A 1st-taper tap and tapping drill to match the screw. Make the mandrel out of any suitable material you have, slightly oversize, and drill a hole right through with the tapping drill. Tap a thread from the headstock end of the mandrel until the end of the tap protrudes a little from the mandrel - this ensures that the thread is not cut to full depth at the end. Make two axial saw cuts in the end of the mandrel, at right angles to each other Insert the screw finger tight, put the mandrel in the lathe chuck and skim it to final size, and the job is essentially finished. The following link should make it all clear. http://tinyurl.com/2lf2tq Put the workpiece on the mandrel and tighten the screw from within the lathe spindle, which will expand the mandrel because of the tapered thread and grip the workpiece securely.
You could, of course, use a long threaded bar instead of a socket screw and long key.
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Thats exactly along the lines I was thinking but your implementation is far simpler and easier to make than I was contemplating, its probably what I will do.
Thanks
Ian

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