"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
"RogerN" fired this volley in
:

Anyone make their own line boring bar/equipment? It doesn't look that
hard to make and could be handy on jobs that are too big for machine
tools. Just wondering if there are any good plans or project info on
these. The stuff looks pretty expensive to buy new for what it is.

RogerN




I made a simple jig that mounts the work on the cross-slide, and holds
the boring tool between centers. It allows me much longer bores than a
single-ended boring bar mounted in the tool holder would.

It's really nothing more than a plate to which I clamp or screw the work.
The boring bar is a piece of 5/8" stock with a hole for the tool bit and
a hole for a setscrew, plus center pockets on both ends. Drive it with a
dog.

About the only drawback is that the bore size is limited to the amount of
tool overhang you can afford; with my little 1/4" bit, that's about
1.25"(or a bore of 2.5" max) before chatter kills the job. And, of
course, you have to adjust the tool on every cut, rather than moving the
cross-slide.

But it works.

This is essentially how the original boring machines worked. Lots of early
automobile engine blocks were actually bored on lathes.

Some of the old English MAP books show miniature versions of those old
boring setups on lathes. Brit lathes, which traditionally have T-slotted
cross slides (or saddles; I forget which) are ideal for that work.

--
Ed Huntress