On Friday 19 October 2007, Brian Michalk wrote:
>Is there an old trick to turning a part exactly on center?
>If this venue is not the right place, I would appreciate a pointer to an
>active group that could help me.
>
>I have 12mm precision round shafting. I need to turn down one end of it
>to .25 inches diameter.
>I have a four jaw chuck, and center to within .001", but when I hard
>couple a stepper motor to this part, it binds due to the .25" boss not
>being exactly on center.
>I do have a spider coupling, but would rather go direct due to the added
>size of the coupling.
>
>Is there some "trick" someone could enlighten me with?
The only quick and dirty way I'd try first, is to let the shaft extend well
past the chuck jaws, centered as well as you can, then setup a follow rest to
force it to the bit by 4 or 5 thou while riding the uncut shaft, and do the
turning to the 0.250" size against that. And I might grind rather than turn
the last .010". I'm in the thought process of taking the bearing cartridge
from the front end of a old dremel and rigging a rigid mount the tool holder
could carry, and spin one of those $14.95 diamond wheels for the dremel.
Those things cut like crazy with a touch you often can't even hear, I even
use them to tune up dull carbide bits here. One might also be able to get
the cable handpiece of the dremel 400 held in a toolpost but I've NDI how
much give there is in that things bearing mount. I've done some decent work
using that wheel and the whole dremel hanging on the toolpost, but on my
teeny 7x12 lathe, its too easy to run out of carraige motions with that
relatively huge grinder, so you can't get at all the workpiece with it in one
pass.
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Although golf was originally restricted to wealthy, overweight Protestants,
today it's open to anybody who owns hideous clothing.
-- Dave Barry
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