Thanks, Mike

[John Hofstetter <hofs@domain.elided>]

>	As for polishing, I used the carbide cutters for that to.  It takes a
>steady hand, VERY light touch, and constant motion to give the metal a
>smooth finish.  It's not as smooth as using grinding stones or pads, but
>smooth enough for the RPM,s an IH will run.  The single cut bits gave a
>smoother finish than the double cut bits.  The bit I used the most was a
>6" shaft 1/2" cylindrical shape ball nose.  For the corners, a bit of
>5/16" or 1/4" is best.  I couldn't find any flame shaped bits around, but
>I think they would have been handy to have.  The bits with a sharp edge
>at the top or bottom caused me problems.  The sharp edge digs into the
>metal and leaves a ledge that would cause airflow turbulence.  If you
>aren't perfect with bits that have all rounded edges, it's not a big
>deal.  You might have a little dip in the metal, but the air will still
>flow smoothly.
>
>Take care,
>Mike Ryan

Thanks Mike, 
That was a very thorough description. It makes me want to go up and help 
John L. do his P and R and re-learn the process.
My doubts about the carbide cutters and the reason I posed the question, 
was that I know how hard cast iron is, and wasn't sure the cutters were 
up to the job, without a lot of chattering and such.
Thanks again.
John H.