Having problems milling brass

CODEMAN

CODEMAN

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I've been trying to mill a 1/4" x 1/4" x 4" brass rod down to 1/8" for the first inch of the rod. Seems like no matter how shallow a bite I try to take, the edge of the bit grabs the piece and tries to pull it out of the vise. I've been using a 1/2" two flute HSS bit. Seems like it's the worst when the bit just starts to cut and grabs the edge of the piece.

Should I go to 4 flute bits?
Should I dull the leading edge of the bits?

I also think that this might have to do with my vise. I got a 3" screwless vise, but have a hell of a time tightening the damn thing down correctly. I'm shopping for a new vise, but still think that the bit is the issue.

Steve
 
It sounds to me like you are "climb" milling instead of "conventional" milling.... if so, your cutter isn't likely the problem.

Brian :)

38772d1317680462-climb-milling-conventional-when-using-carbide-climb_conv1.jpg

38772d1317680462-climb-milling-conventional-when-using-carbide-climb_conv1.jpg
 
Hello Steve,

Do you have a smaller 2-flute endmill ... like a 1/4" or 3/16" ? Maybe try that with a higher spindle speed. A 4-flute might give better results as well.

What spindle speed are you using ?

Brian :)
 
How fast is your spindle turning? Too slow and it will grab quick.

Billy G"
 
Is it possible to clamp the part to your table and try it that way? It really sounds like your vice is too loose. Maybe you could put a C-clamp on the vice to help hold the part? If you have one, a smaller end mill might help.
 
2400 RPM is way too fast for brass. Stick to around 7-800 RPM, use a medium sized cutter (1/4") and try that with a slow feed.

Seems like your vise is the problem, try clamping a brass scrap piece to the table with toe clamps. It should be fine clamped to the table.

I've never had a bad experience with brass, turning or milling. Somethings fishy....
 
Hrmm... two things come to mind... IF you are not climb milling, as you say...

How much of the rod do you have sticking out of the vise? Go for as little as possible. If you need to mill an inch of the rod, have about 1-1/8" sticking out.

A screwless vise is not the optimum vise for this type of thing, for sure. Do the jaws have V-grooves in them for round stock? If not, when you put the rod in, put it on the very bottom of the vise opening and try to tap it down with something as you tighten it. Perhaps a 3/16 rod or something. Then tighten it as well as you think you can, without reason.

I'd imagine you've already done these things, but we may as well cover all the applicable bases.

One final thought is how you're feeding it in. You can either feed the end mill across the part perpendicular to the rod, or parallel with it. I personally would feed it perpendicularly, in the Y axis assuming your vise is aligned in X (left-right), taking perhaps .300 wide with a 1/2" end mill...
 
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