Tapping Oil ? For tapping Acme thread in bronze.

[754]

I have cut a few Acme threads in bronze... usually one or two on a job, and i single pointed them.. likely used a biypt of tapping oil..it was a while back.
so now I have a dozen to do, 3/4 by 6 TPI.. bronze 2 1/8 long. Customer supplied 2 stage tap. I neither want to seize it on tap, nor spin the bushing in tge chuck jaws, and I would like nice threads.
Anyone here tap bronze often ? What do you use ?

[nickel-city-fab]

I can't say that I have much experience in bronze, but I do know that sulfur oils react/break down copper and therefore they might make the job easier. You would just have to make the parts *very* clean afterwards to prevent further erosion.

[Fasturn]

Taps well with Molly Dee- as per manufacture clean after or it can stain copper. This is Bronze, the stuff that can be in the elements for years. If your coustomer has no requirements or restrictions, then you are good. Stinks but works very well.

Thats a big tap and I would modify the lead more if it give you trouble. Done alot of progressive tapping. You might end up in three stages? Let us know how it worked out?

[JoeLee]

I don't tap bronze often but have tapped and single pointed a fair amount of it in the past. I've used Rigid pipe threading oil and a few other lubricants such as WD40 and never really noticed any difference. I've also single pointed with no lube. Every thing still came out nice. Bronze has a self lubricity quality and I've always found it to machine nicely.

JL.............

[tom_d]

All the brass and bronze threading I've done dry. No fluids at all. On a few where the chips were getting in the way I used a spray mist nozzle with air only.

[754]

Its a 2 stage tap, first part having a V thread to rough it out, then changes to Acme with lots of start taper.
i wasplanning to run the v thread roughing section thru, then back it out. I have a sliding tapper that does not have enough length for the tapping , in one go.
i planned on running the v thread thru all pieces, then letting them cool. Then remounting on the V portion, then clamping in the 3 jaw, then running the Acme portion thru under power , the sliding tapper will be long enough for that.
The tap is from KBC, I think..

[old mart]

I bought leaded gunmetal to make ACME nuts and machined it dry. The spec in the UK IS sae660.

[nickel-city-fab]

i was planning to run the v thread roughing section thru, then back it out. I have a sliding tapper that does not have enough length for the tapping , in one go.
i planned on running the v thread thru all pieces, then letting them cool.

Aww man, you don't get to hand tap it?

Lower the speed, less the heat.

[Fasttrack]

Next time I'm in the office, I'll check what I use for copper. I got it from Enco way back when for machining pure copper heat sinks. Very sticky, nasty stuff to machine so a high quality lubricant to prevent chip weld and achieve really clean, smooth surface finish was needed. I've been happy with it but I can't remember the name... I don't do much in copper or brass anymore.

If you need something quick maybe give this a shot? https://www.mcmaster.com/cutting-flu...um-and-copper/

[darylbane]

I think I remember in the olden days, you can use milk for bronze. Seems like it might make a stinky mess though.

[john b]

I have used milk on copper, 45 + yr ago, it only stinks if you don't clean up soon after you're done.

[Bented]

Next time I'm in the office, I'll check what I use for copper. I got it from Enco way back when for machining pure copper heat sinks. Very sticky, nasty stuff to machine so a high quality lubricant to prevent chip weld and achieve really clean, smooth surface finish was needed. I've been happy with it but I can't remember the name... I don't do much in copper or brass anymore.

Lard oil works excellent on copper.

[tom_d]

Its a 2 stage tap, first part having a V thread to rough it out, then changes to Acme with lots of start taper.
i wasplanning to run the v thread roughing section thru, then back it out. I have a sliding tapper that does not have enough length for the tapping , in one go.
i planned on running the v thread thru all pieces, then letting them cool. Then remounting on the V portion, then clamping in the 3 jaw, then running the Acme portion thru under power , the sliding tapper will be long enough for that.
The tap is from KBC, I think..

While bronze can normally be cut dry it can generate a small amount of heat. If you're concerned about dissipating the heat then a water based coolant will work. Where bronze is copper based, products containing sulfur should be avoided to prevent staining of the material. One that I've had good luck with is Anchorlube. Use it straight, or thin it 50/50 with water. Manufacturer refers to it as G-771.

[754]

I have anchorlube, or should have , used it sometimes.
Ok had 12 pieces to do 2 1 /8 long. First one cut fine, not much heat. Backed it up a bit, a few times. Just put some motor oil,along the topmost row of teeth.
could use a longer sliding tapper, need around 6 inches of travel.
nothing seemed out of sorts, it went fine. At the end i pulled tap out of holder and notice about a 1.75 long piece of teeth missing from the first roughing stage of tap... WTF ? Dont know when or why it happened .. strange.

[JoeLee]

I have used milk on copper, 45 + yr ago, it only stinks if you don't clean up soon after you're done.

Milk?? that's a new one. Was it regular milk with all the fat??

I remember my father's Uncle used to wash out his baritone tuba with milk.
That was the first time I ever saw milk used as a cleaning agent.

JL....