Brian – Have you ground flats on the cutting lips of the drill, parallel to the drill axis? (to remove the helix lead angle in the lips)

Look up "grinding drills for brass" on Google if you are not sure what I mean.

This will reduce or eliminate snatching during drilling in brasses and bronze (except in thin sheets) . Drop of good cutting oil doesn't hurt either.

In thin sheets, a stepped "Christmas tree" type drill works well.

Good luck, JD

Brian,

This appears to be already set-up on a mill …

My preference would be to use a milling cutter, or a single point boring tool: either of these would be lower risk than using a drill.

MichaelG.

I am building up a set of brass drills by taking the cutting edge of the lips by dressing off with a diamond hone… it only removes a couple of thou' but it's enough to stop the 'grab' if through drilling, or pulling effect in a blind hole.

George.

I have seen accidents with drills grabbing bronze,grind flats on the drill lips on a grinding wheel ,you require a visible flat not a bit of honing on a half inch drill,and on the casting in the photo I would use two clamps,better than wrecking a casting, the correct method would be to use a straight fluted drill or straight fluted milling cutter.For one offs a boring tool in the mill is possibly the safest option.For cutting fluid I would use ordinary soluble oil,cooling the tool is more important than lubrication,When drilling drawn phosphor bronze,possibly the worst material for "snatching" start off with minimum depth of centre drill and then drill to required size with one drill,grind the drill so that one cutting edge is slightly longer than the other one so that the drill make a slightly oversize hole as drills not only snatch in bronze they also tend to bind in the hole if the depth is greater than 2x dia.

There is a picture here

**LINK**

Martin

Fair comment from Nigel. I do tend to put bigger flats on larger size drills and it is possible to do it on a grinder but for a first go hand work with a stone is more controllable.

Martin

There is indeed.
Thats why the bushes made from tube don’t count

Puting it in the lathe with a four jaw and a small boring bar would work, as I just done that yesterday when I had to make a phosphor bronze cylinder with a 8mm bore.

I read this thread and started worrying. You see, I have decided to make a bronze bush to allow a steel leadscrew to rotate in a steel bracket. I decided to thread the outside of the bush and thread the inside of the bracket and then fix the two together with Loctite Studlock. Possibly OTT, but I wanted to prevent the bush being pushed out either way from the steel bracket.

I have so far faced the end of the bar using a homemade knife tool made from an old file. Then I surfaced an appropriate amount using the same tool. Next, I cut a groove to mark the core diameter required, hence marking the depth of thread, using a homemade parting off tool, again made from an old file. And finally, I cut a 18mm diameter 1mm pitch thread on the surface of the bush using a homemade 60 degree single point threading tool made from square silver steel.

I used Neatcut whilst cutting the thread, otherwise I cut dry.

No problems whatsoever. Indeed, it was so easy that I do not anticipate any problems with the final cut to create a 10mm through hole.

The bush, by the way, is to be made from Phosphor Bronze to L62/SAE 660. At least, that is what someone, not me, has written on the bar.

What am I doing wrong to avoid all the problems?

Regards,

Peter G. Shaw