ol3_m3 wrote:
Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?

thanks

OM

If money is not an object, get a core drill of appropriate length. Try
the local tool supplier, or McMaster Carr.

If you gotta do it on the cheap, turn down the shank on a 3/4" drill
or use a Silver and Demming type drill, and solder an extension onto it.
A little creative grinding and it will have it's own pilot.

12" isn't all that long a hole, in the scheme of things.

Cheers
Trevor Jones