Paul,


Do you recall the size of the adjustable boring bit your friend used on
the Bridgeport?
For a two inch step I imagine the boring head couldn`t be much bigger
than 1 inch in diameter.
 I`ve seen lots on E-Bay for sale but most are two inches and bigger.

Doug in Japan.

The boring head can be much bigger than the hole.
The size of the head has little to do with it.
A 4 inch diameter boring head could cut a half inch hole.
The size of the cutting tool has more to do with it.
The cutting tool can be located anywhere from the center of the head out to
the max radius of the boring head. The whole idea of a boring
head is the radius of the cutting edge can be adjusted down to .001 or below.

Paul Lamar

Paul,

Thanks.  Now the penny dropped. Boring bars.  Yes we have boxes full of
them in different sizes.  I will have to find out what type of thread is
on the local end mills before I order a boring head though.


Doug in Japan

I think you are talking about the taper in the end mill spindle.
Boring heads come in different tapers. They also can be had with
a simple cylindrical shank about .75 inch in diameter. That is the
route I would take as then they can be held in an ordinary collet which
most end mills can accommodate. Take some pictures of the end mill tool
holders used and I can probably come up with an strategy for holding
the boring head.

Paul Lamar