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What bronze alloys would be best for fine threading and small machined parts.

laminar-flow

Stainless
Joined
Jan 26, 2003
Location
Pacific Northwest
We used to make some parts out of 360 brass for a customer but now they are requesting a 954 bronze alloy since it does not have lead and is EU compliant. Will 954 be a good choice for fine threads and small machined parts? Would any other no lead bronze alloy be better than 954?
 
I haven't ran any bronze alloy in ages, so all I can remember is depending on alloy you can get round stock so badly out of round and tapered it cannot be run through a collet and I am talking a 16c that you can run material +/-.010 of the nominal size through. Another issue I remember is the surface imperfections were also pretty deep.
 
Go to McMaster and look at the listed tolerances for bronze rod they are huge on 954. I would start my shopping there, lots of good info.
 
Hi laminar-flow:
Once you solve the stock geometry issue, you will find that 954 aluminum bronze is very nice to work with and holds detail well...much better than brass because it's not so damn fragile...it can tolerate a bigger bump without bruising like a whiney baby.

A couple of caveats though, which are true for pretty much every aluminum bronze I've ever worked with.
These materials are hard to drill, hard to ream, and hard to tap.
Not impossible, but definitely can't be approached as casually as 360 brass.

I have found threadmilling to be superior to tapping across all sizes; I've found single point boring to be more predictable than reaming, and I've found helical interpolation more predictable than drilling when the LD ratio allows.
When it doesn't I've found playing with the cut parameters helps and I expect to break a few tools until I get it dialed in, so budget for that.
The problem is that the material tends to shrink and grab on the holemaking tool and will twist it off in a heartbeat.

With regard to rough stock; that's what centerless grinders are for...yeah it's expensive but so long as you know beforehand and quote accordingly, it's not a show stopper.
That's how the Swiss guys typically solve a problem of that kind.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 
You will find that machining aluminum bronze is nothing like machining 360 brass. You must keep your tools sharp- as soon as a tool starts to rub the slightest amount, the bronze will work harden and you're screwed. Once you figure that out and respect its properties life will be ok.
 
You will find that machining aluminum bronze is nothing like machining 360 brass. You must keep your tools sharp- as soon as a tool starts to rub the slightest amount, the bronze will work harden and you're screwed. Once you figure that out and respect its properties life will be ok.

yea, sharp tools are pretty good for all kinds of materials.. but what degree of rake is good for AlBr? zero to a few degrees negative like for 360 brass, 0 to a few degrees positive like 655 silicon bronze?
 
We make some parts out of 464, I think it is 3/4 to full hard. It is non leaded and machines with more difficulty than 360 but not terrible. 464 would be a piece of cake compared to 954. The size we use the most is 1/4 inch but it is available in smaller rounds.
 
Hi cyanidekid:
You wrote:
"...but what degree of rake is good for AlBr? "

I've found that I have a really hard time breaking a chip with 954...the material is so tough that it's hard to get it to curl quickly enough to prevent bird's nesting.​
Now I don't do production turning so take what I say with many shovelfuls of salt, but I've had best success with a dead sharp positive rake insert for aluminum for the kind of prototype turning I do.

I've tried with negative rake and with honed edge inserts and I just raised a humungous burr and work hardened the stock as Dan from Oakland has pointed out.

Finding a balance between pushing hard enough to break a chip and pushing so hard that you just wipe out the insert is always a problem in tough, ductile alloys...the window is narrow.
So you may find you break your head far more over controlling the chip than you ever do about actually peeling it off the bar.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 
The 954 Bronze was a delight to deal with. The stock from Mcmaster, (in a rush), came in at just over .375 so there was more milling than needed. Yes, did them in the mill and thread milled the 190-80 threads. I'll look for some .250Ø material for next time.
 








 
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