Given that you have a rotary table and that you're cutting phosphor bronze,
I would strongly recommend not using a spin fixture.

Although I've never machined silicon bronze before, I would assume it's
probably at least somewhat grabby. You're going to have a tough time
controlling your feed. You'll probably end up breaking cutters and you may
smash a finger or two. You would _never_ see me or one of my coworkers doing
this at work, ever.

If you don't want to buy a chuck for your rotary table, and you only have to
do 4-8 pieces/month, one or two setups/month, I would use a v-block. Simply
indicate the rotary table to your spindle, and then the part (now clamped in
a v-block which is lightly clamped to the table) to the spindle as well.

If you don't like the idea of having only one screw clamping directly on
your part, some soft jaws in a simple clamping mechanism could be made. If
you're getting paid for your time, a cheap chuck is probably cheaper, but
perhaps not if you're quick. Ned's idea is a good one. Sometimes collets are
a bit funky to deal with as far as adequate clamping pressure - esspecially
on bearing materials.

Once your setup is done, the cutting time should be minimal, on the order of
60 seconds/pass. You should have no trouble roughing and finishing with the
same cutter. Switching parts would take roughly 30 seconds, including
brushing the chips off the block between parts. Resetting the machine after
each part would take about 30 seconds.

Total cycle time should be 3 minutes. Setup would probably be about 60
minutes, start to finish.

This all assumes you don't want sharp internal corners.

Regards,

Robin



"John Flanagan" wrote in message
...
Dear All:

I've got a part I need to machine (repeatedly) and was wondering if
anyone might make a suggestion for an effective and inexpensive
method. A photo of the cut that needs to be made can be found he

http://vulcan.blacksburg.net/~flanag...eeve%20RFS.jpg

You can see the collar on the upper right part has been cut ~90°.
I've been thinking of using a 5C collect in one of those cheap spin
indexers you can get at ENCO for ~$30. The collar is less than .250"
thick by ~ 1" wide, material is silicon bronze. I'm a little
concerned about controlling the part as I spin it by hand since the
spin of the indexer is direct without gears and can (I think) move
freely front to back while spinning). A photo of the spin indexer can
be seen here;

http://www.use-enco.com/CGI/INSRIT?PMAKA=235-6011

The only other solution the I can think of, for a professional looking
finish at least, would be to use a $$$ super spacer or to buy a chuck
to mount on my rotary table with the 3MT center (which has it's own
problems of set up time and PITA factor).

Thanks,

John

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