On Jul 8, 10:40*pm, "DoN. Nichols" wrote:
On 2009-07-09, Michael Koblic wrote:
...
* * * * Hmm ... first trick is to make sure that the tool is quite
sharp.

* * * * Second is to feed something like 1/3 the distance to reach final
diameter, make your cut, and measure what you really got, comparing it
to what you expected. *Divide what is left by two, and adjust by how far
off your previous result was. *Feed in that much, and make another cut
and measure again. *Adjust again for the final cut.

* * * * It is difficult to get a very light cut to produce what you
want, because deflection of the workpiece and the tool may prevent ever
taking a bite, so when you finally feed enough to take another bite, it
is too big. *So sneaking up on the final dimension can be difficult, and
making larger cuts works better.

* * * * As for getting the boring to work right -- bore to a few
thousandths undersized, and then use a reamer to get to final size. *The
same problems with sneaking up on the size occur when boring as when
turning -- perhaps more so.

You can check if the tool will shave off a fraction of a thousandth
while you're still a few thousandths out and can safely remove and
hone it.

When I have difficulty with a fit I make the start of the bore or the
shaft slightly tapered by filing or cutting steps, press the parts
together enough to make marks, then cut down to almost remove those
marks. Candle flame soot or marker ink makes them easier to see.

jsw