Cracked a Sand Cast Sideplate

[Bill-52]

Was drilling a sand cast brass sideplate - the shaping, filing and preliminary finishing was done.  Rear lock bolt hole also drilled, no problem.  Annealed the sideplate (again) and started drilling the front lock bolt hole.  I felt the sideplate getting hot but as I was almost through (1/32nd to go?), I decided to push ahead.  Bad decision.  The sideplate cracked above and below the front bolt hole.

Other than bad decision making on my part, is there anything special about sand cast brass that I should have known?  I've only worked with wax cast and plate brass in the past.

Thanks,
Bill

[billd]

Sharp drills, don't force it, clamp your work securely.   Did it grab when it broke thru the hole?  If so, a small flat on the cutting edge of the drill helps.

Bill

[Stophel]

If you can, run a little silver solder in the cracks to fix it right up. 

[docone]

It brazes like any other brass.
Use a small torch, brazing rod that will match the colour of the piece, and use a solder board.
Borax makes the best flux, muriatic acid cleans the flux.
Should go well.

[E.vonAschwege]

I use silver braze that is brass colored for use on musical instruments - repairs are virtually invisible, and can even braze together Frankenstein triggerguards, buttplates, etc.  Got it here: http://www.votawtool.com/zcom.asp?pg=products&specific=johronp4  flow temp is a little higher than I'd prefer sometimes, but works very well.  I use staysilv brazing flux. 

Biggest trick I ever learned for drilling metal was to slow down the speed and apply constant steady pressure - if the piece is getting too hot then your drill bit might have been dull.  Good luck,
-Eric

[chubby]

When drilling harder material you should have a lesser point on your drill & slower speed. When looking at your drill, less of a v for hard. And more of a v for softer metal. Based of off a standard 118 degrees. Chubby

[Acer Saccharum]

Sharpen drills special for brass and silver. This changes the cutting edge to a scraper instead of a chisel. Drill won't grab as you beak thru the other side of your work.