What's easier, machining brass or aluminum?

[johnm]

Folks -

I have a prospect that wants us to make a branding iron for him, either out of brass or aluminum plate, looks to be about 1/4" thick, 6" long and about 1.5" wide. I would have sufficient space to screw the plate down in a waste area.

He doesn't have a pref regarding mat'l, so which of them is easier to machine, and can anyone give me some pointers, feed, speed, bit, and the like...

We have a 3hp spindle and the letters, in reverse, look to stand proud of the background by about 1/8".

I'd appreciate any tips and thoughts - we've never machined metals before.

John Moorhead
Rose Davidson
Sleeper Woods Design

[Brady Watson]

Brass...for a number of reasons. When working with metal, be VERY conservative on your speeds and depth of cut. MOST importantly, hold the brass down REALLY WELL!

You would probably do best with an end mill and spindle speed around 10,000 and a move speed of .4 to .7 IPS XY and .1 to .2 IPS Z.

-Brady

[elcruisr]

Everything will depend on the alloys of either material available. In both materials there are alloys that machine well and some that are very troublesome. It will require tooling meant for the job and possibly some form of coolant. In general, at least from hearsay, aluminum is going to be easier to deal with, depending on the alloy. You might talk with a tooling rep or manf. They are usually very well aquainted with what alloys work best with what tooling.

Eric

[Brady Watson]

Eric - good point. If you are going to use AL, then 6061 is nice to machine. For your application though, brass is a better choice & what is used commercially (like the Rockler stamps)

-Brady

[wcsg]

It will depend on your alum and bit makers. 6061 is a harder alum while 5052 is a softer Alum. I use Belin Bits 1/8" & 1/4", speeds between Alum & Brass are different with brass being slower in feeds and RPM's. I've only cut alumunim and my speeds are such on my 3ph Spindle

1/4" shank 1/8" CED 18,300 RPM @ .40" IPS
1/4" CED 12,200 RPM @ 1" IPS

with slow z speeds like Brady had listed like .2

I have a mister which I still have yet to hookup but I just sit and squirt with WD-40 every 30 secs or so

[don]

John,
I would have to say that Brass would be the easiest to machine, But I'd choose a Carbide tool, it'll handle either material.
I don't know how many your going to make. But if I was going to make very many of these I'd polish the flutes of the tool before even starting.
I've seen both brass and aluminum stick to both hss and carbide tools and end up ruining the part and tool. I know this sounds trivial. But by having the flutes of the tool polished, its slick and the material won't drag.
A year ago I used compressed air with a small nozzle pointing to the point of impact of the tool and material. That is until I purchased a cold air gun. I have it fixed to my dust shoe so it blows in the direction of the dust collector pickup.

Don

[gus]

John,

I have used the .25" tool at the bottome of this page http://www.use-enco.com/CGI/INPDFF?PMPAGE=105&PMITEM=325-2348
to mill out vaccume fixtures from 1" thick 6061. I use a PC router 10,000 - 1300 rpm feed at 1.7 to 2.5 ips and use smaller stepdown and stepover. This is done dry and I only use air to keep chips from building up around tool when cutting a deep slot. I find it better to remove the dust shoe and let the air blast from the PC help clean the cut and just let the chips fall where they may.