Drilling Copper

[4156df]

Hi & help please.

I'm attempting to drill copper and having less than satisfactory results. Note the mushroomed entry and the stretched out exit.

I don't know what the alloy is, but it's from a 4" copper sweat coupling. The holes are 3/32" and were drilled with a standard HSS jobbers bit (brand new). Speed was 4250 rpm with Tapmatic Gold fluid brushed on for cooling. I kind of peck drilled (about four pecks to get through the 1/8" wall) and applied coolant between each peck. If I didn't peck, the bit just quit cutting.

I don't have much extra material to experiment on and I have a lot more holes to drill, so I'm hoping someone can point me in the right direction.

Regards,
Dennis

 

[Maryak]

Dennis,

If it were me, I would:

Halve the speed.

Stone the drill on the cutting edges.

Check that the drill has a small amount of back rake - looks like it's rubbing.

Hope this helps,

Best Regards
Bob

 

[stevehuckss396]

I drill alot of copper buss at work and the first thing we do is resharpen the bit with more of a point. Cant give you the angle because we just eyeball them. The copper seems to "smear" less and we get a crisper hole. Common sizes are 1/4 and 3/8 inch holes. Cant tell you if it will work on a hole as small as yours.

 

[rake60]

Copper is a gummy material to machine.
It requires very sharp tooling and some kind of a cutting
fluid to reduce the loading up on the cutting edge of the tools.

 

[rleete]

I did a copper flywheel a while back. Trying several different cutting "fluids", I found plain old Cristco to be the best. Some of the forums have indicated heavy cream works, but I was too chicken to try that (imagine the smell if you didn't get it all cleaned up!).

 

[scoop]

Try starting with a slow drill speed of about 500 rpm and use a dab of cooking lard for a lubricant.High drill speeds are not required on copper as it just hates to be cut and just pushes out of the way of the tool.Also when the lard gets hot it smells like chips (fries if you must) cooking,quite nice really.

good luck best regards Steve C.

 

[tel]

So enquiring minds want to know - why copper???

The stuff is a total ***** to drill, file, machine, tap or saw.

 

[4156df]

Hi and thanks for the responses.

I tried a slower speed (1325 rpm) and that really made a difference. Didn't have any Crisco or I'd have tried that too. At this speed I get a nice continuous chip, particularly if I really pay attention to the feed rate. There's a lot less smear out on the bottom side also. The slower speed seemed counter-intuitve to me as I've always thought, "the smaller the drill, the faster the rpm."

High speed (4250 rpm) is on the bottom and slower speed on the top (1325 rpm):

tel.....The short answer to your question of "Why Copper" is ignorance. While I had read about copper machining problems on this board, I figured that since all I was doing was facing the edges and drilling a few holes, it wouldn't be a big deal. The biggest reason though is that this fitting had the ID and OD I was looking for.

Thanks again to all of you for the help. This board is the greatest!

Regards,
Dennis

 

[mako20]

I agree with the slower drill RPM. I also use a watersoluble coolant and keep the drill point flooded. I use just a plastic squeeze bottle for the application. Hope this is helpful.

 

[Bluechip]

Hi Folk

One place I went to did Bus Bars & Sacrificial Anodes in thick copper.

They did 'em with Spade Drills. Bigger than your sizes though. About 16 - 22 mm IIRC.
Used milk & turps for lube, stinky buggers ..

Dave