A/B Nuts: Brass or Aluminium?

[snooper]

Assuming galvanized threaded rod for the screw, which of brass or aluminium would be better suited for material for the nut? Most of the ones I've seen here were made from brass, but the extra alu cut-offs I have lying around got me thinking...

[Geof]

Not suitable. Aluminum is a very poor material to use for a nut, it is too soft and is likely to gall up and seize. And if that was not bad enough the thread will fail due to fatigue if it experiences a cyclic or reversing load. Stick with brass or bronze.

[snooper]

Thanks, Geof!

Is it very difficult to cut thread in brass? I haven't worked with it before, and would like to know what I'm up against.

[Geof]

Originally Posted by snooper Thanks, Geof! Is it very difficult to cut thread in brass? I haven't worked with it before, and would like to know what I'm up against.

Brass is probably the best material to work with. Tools must have zero top rake, speed around 400 fpm with high speed tooling and two or three times that with carbide (this is from memory so I hope it is close to what Machinerys Handbook says or I will be blasted), coolant is not essential. The only disadvantage to brass is that the chips come off as a fine spray of little slivers that get everywhere so sometimes I use coolant just to help contain the chips.

Bronze can be much tougher and there are many variations. The best top rake can vary depending on the bronze, speed may need to be much lower than brass, coolant may be needed. And you will probably go nuts (no pun intended) trying to cut a small diameter internal thread in bronze.

[Willbird]

One thing to be wary of with bronze and some brass, a conventionall twist drill will SUCK itself right thru a pilot hole if you do not dub the flutes so as to take away the rake, just like you webthin a drill but at 90 degrees not as you usually do matching the helix angle. With a large drill the grabbing action can be pretty dangerous as it will yank a handle right out of your hand...as long as nobody gets hurt it can be good for a real laugh when you see the reaction of the guy it happened to. If your working with a drillpress it will lift a large vise clear off the table when the quill runs out of travel, I saw a guy do this with a large taper shank drill, when the heavy vise got up off the table several inches the vise started to turn with the drill, the drill borke, the vise went flying. Nobody got hurt anyway.

Bill

[venomx999]

use plastic, its less abrasive.