Tip from a machinist

[JAinVA 4,619]

While working on a weight rack for the crane tractor I found that I needed to open up 3/8" holes to 25/64" or larger. If you ever had to  drill a hole by the next size up or 2 in thin metal then you know the twist drill will grab and spin in the chuck or worse snap off the cutting edge.

If you have access to a bench grinder this trick will solve that  problem. Grind a flat at the cutting edges so that the drill resembles a spade drill. It will still drill and not grab.

Edited November 19, 2020 by JAinVA

[Ed Kennell 35,616]

This drill treatment also works well to stop grabbing when drilling holes in soft metals or plastic.

[JAinVA 4,619]

Right Ed. We routinely did this to drills when working with brass or copper.

Edited November 20, 2020 by JAinVA

[Zeek 2,284]

Hmm, interesting. I destroyed two bits (with oil) grabbing in this steel for a hitch brace. Broke chunks right off. Good to know.

[JAinVA 4,619]

In steel ,pilot holes should be drilled first. Depending on the angle ground on the  cutting edge by this method,,drilling in steel can be difficult  This works best in steels if you need to drill a larger hole.

Edited November 20, 2020 by JAinVA

[Zeek 2,284]

10 minutes ago, JAinVA said:

In steel ,pilot holes should be drilled first. Depending on the angle ground on the  cutting edge by this method,,drilling in steel can be difficult  This works best in steels if you need to drill a larger hole.

 

I always do pilot holes and work my way up, but this stuff was exceptionally tough. I finally resorted to a drill press with oil and just worked it slow until it got through.

[Pullstart 59,561]

I agree!  Brass especially, drills like buttah (see what I did there EB?) by slapping a reverse angle on the bit