Re: (ET) BB600 status and some failures.

[Chris Tromley <ctromley gmail com>]

On Sat, Mar 4, 2017 at 4:31 PM, Christopher Zach <cz alembic crystel com> wrote:

By grinding the bolt flush with the post and using a 10/32 tap and drill set I was able to get four of the cells drilled, the old bolt drilled out, and new threads tapped. Of the other three one had a drill bit in it already, and I broke two bits trying to drill out the remaining two. So now I need to drill through drill bits. Not fun.

​Not familiar with BB600s, but drilling out drill bits will be tricky business.  I've never had to do it myself.  If presented with that problem, I'd hope that the drill I broke off was made from high-speed steel (the most common type).  Then I'd go to McMaster-Carr or some othe​r industrial supply house and get some carbide drills.  Not sure if carbide is hard enough to make that work. Maybe search on what you're trying to do first, and you'll likely get some hits on machining discussion forums.

Typically you remove a broken drill bit by EDM.  But that requires immersing the BB600 in a dielectric liquid, which would likely be hard to keep out of the plates.  Or not?

Good luck,

Chris