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Karl H
11-03-2007, 10:38 AM
The .250 brass plate we get is laminated(consulted a wise machinist) but the solid brass(320/360) I drill wants the drill to pull through. I tried a brand new drill and the first pass shattered the top of the brass. What can I do to stop these two conditions? I don't feel I have control of the drill when this happens. Thanks -K-

Lew Hartswick
11-03-2007, 10:52 AM
You have to "dub" the cutting lips. That is reduce the rake of the
cutting edge to 0 deg. Same thing for a turning tool on a lathe, no
top rake. That prevents it from "screwing itself into the work".
In our drill index we have such modified drills for all the common
used ones in an small envelope marked "for use on brass" . Even the
high school students "get it" after a while. :-)
...lew...

Mcgyver
11-03-2007, 11:12 AM
like Lew says, you need zero rake to machine brass - just made a post on the chaski board on how to put zero rake on the drill......not one response so i thought maybe it was a crappy post or they all know how to do it already :) , maybe it'll help you.

http://www.chaski.org/homemachinist/viewtopic.php?t=77682

Virgil Johnson
11-03-2007, 11:53 AM
Using the power feed (I assume this is on a mill) with the quill lock ever so lightly snug may help in this situation. Works for me on plastic and brass.

rkepler
11-03-2007, 12:47 PM
There are also drills made for brass, low rake and a very low angle helix. It's not likely worth getting a set unless you're doing a lot of brass work.

(I once had a 1/4 aircraft drill pull into some bronze fast enough that the quill feed handle on my mill gave me a pretty good whack. I think I learned something that day.)

Karl H
11-04-2007, 11:17 AM
Thanks guys for the information on brass drilling. The pictures were very good! Thanks again for the input. -K-

DR
11-04-2007, 12:13 PM
Yep, drilling brass can be dangerous, a normal drill will grab and spin the part if hand holding.

Modify the drill as mentioned, also clamp the workpiece down securely.

If the part is held in a vise on a mill and the power feed is used then a normal drill is okay.

Generally speaking, almost all thin metals can be a problem to drill, punching is the preferred method.

aostling
11-04-2007, 04:08 PM
That prevents it from "screwing itself into the work".


I knew about the 0 rake requirement, but wasn't quite sure why it was necessary. Your simple phrase sums it up in a neat nutshell, which I won't forget.

Nick Carter
11-04-2007, 04:14 PM
Here are some pics I took, showing how to do it with a stone:
http://www.flickr.com/photos/cartertools/732106578/
http://www.flickr.com/photos/cartertools/732106594/
http://www.flickr.com/photos/cartertools/732106614/

I usually use a grinder for larger bits but for smaller ones I find a stone more controllable.
Nick


like Les says, you need zero rake to machine brass - just made a post on the chaski board on how to put zero rake on the drill......not one response so i thought maybe it was a crappy post or they all know how to do it already :) , maybe it'll help you.

http://www.chaski.org/homemachinist/viewtopic.php?t=77682

Karl H
11-09-2007, 07:50 PM
I thank you guys for helping me out on drilling this solid brass. I do drill a lot of brass, but I get gun shy when it comes to over .250. Now I have some weapons to combat this thanks to you! Now if I have this clear-I need to grind/file a flat perpendicular to the shank equal to the relief of the cutting edge? Thanks -K-