What's the best way to drill copper?

[paulhorth]

When I finally receive my new boiler, for my 2 inch traction engine, I will have to drill the ten copper hornplate stays and tap them 2 BA. I do not want to break a drill in the stay. What lubricant should I use? Is fast or slow speed best?
All advice appreciated.
The rest of the engine will have to be reassembled on to the new boiler. I decided to replace my home built boiler last year after finding leaks at the firebox tube plate.

Paul

[weldsol]

Good old fashioned full fat Milk works well

Paul

[Shawki Shlemon]

Copper is soft I would drill the holes for tapping slightly larger ( a few thou s) to avoid breaking taps , the metal will stretch as well as being cut while tapping ( plenty of lubricant).May be practice on a scrap copper rod of similar size .

When I built the boiler for my traction engine I drilled the holes in the stays prior to fitting them on the boiler.

[Nigel Bennett]

Are you sure they're copper stays you're drilling and not bronze? Bronze can be a pig to drill and tap, depending on the grade used. Like Shawki says, drilling a bit oversize is a good idea, whatever the material in this situation, especially if you've got a decent length of thread.

[bookworm]

White Spirits also works well as a lubricant.

[russell]

I would drill with a number 21 drill for tapping 2 BA. This gives about 65% thread engagement which is plenty. I use Rocol RTL compound for difficult tapping jobs and haven't broken a tap since I started using it (touch wood!).

Russell.

[paulhorth]

Thanks guys, I'll let you know how I get on. I will go and get a stack of No. 21 drills.
When I built the first boiler, the stays were in bronze, and I did break a drill. I managed to get it out luckily. I think on the new oiler, which I have not yet received, the stays will be in copper as this seems to be a new code requirement.

Paul

[paulhorth]

That should be BOILER not oiler !