Rounding over brass bar stock with router -- metal machining advice for a woodworker

[Edward Morimoto]

Hi, I have a project where I'd like to roundover the edges of 1/4" x 1" brass bar stock with a router with a 1/8" radius roundover bit resulting in a cross-section akin to a 1" (Festool) domino. I've done a little cutting/grinding of brass (mostly small dowels), but this will be first time I'm trying to use the router.

As I'm concerned about brass filings falling into the router motor, I've ruled out the router table and will, instead, plan on a making a little fixture to hold the stock (I need to process 12+ pieces 12" long) so that I can use a hand router more comfortably/quickly. I assume I should run the router at a relatively low speed.

But as this is the first time I'm trying something like this, I thought I'd see if anyone had any thoughts, advice, warnings about what I am trying to do. I also have some specific questions from those who have experience machining brass with a router:

1. With a 1/8" roundover bit, I'm not removing much material. With wood, I wouldn't hesitate to make the cut with a single pass, but with brass, should I plan on taking multiple, shallower passes?

2. Can I safely take a single 12" pass w/o stopping to let heat dissipate? I wasn't planning on using any kind of cutting fluid (but please let me know if maybe I should -- it just seemed like it would make a tremendous mess). As I will have to reposition the stock after each pass, I am hoping that a 15-30 second pause between passes might be sufficient to prevent cooking the bit.

3. I purchased a couple inexpensive carbide roundover bits for this (as I thought I would save my Whiteside roundover from the abuse) -- I'm looking at something like 50'+ of total edge machining but hoping two bits will be enough to finish the job w/o sharpening/replacing them (I don't have any experience sharpening router bits). Is that a reasonable expectation?

Thanks in advance for the advice!

Cheers,

EM

[Maurice Mcmurry]

I was Ships Carpenter on a 1952 Norwegian coastal ferry that was being converted into a floating hospital. Occasionally the very savvy Engineers would bring slabs of brass to the Carpenter's locker to fabricate into obsolete parts for pumps etc. They used the table saw with carbide blade and routers with carbide bits. No cutting fluid, working very very slowly. I generally found another place to work when the Engineers were in the Carpenter's locker (like down in the engine room on the lathe or mill).

Brass has some nasty characteristics, A tendency to catch a tool and pull it in.