Having problems milling brass

Can you hold it from both ends, mill it down in between the vises and then cut off one end? I assume you're talking about ending with a square cross section centered on the original?
 
CODEMAN said:
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
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If the piece moves at all in the vice, its not being held in tight enough. That is problem number 1. Fix that before doing anything else.

Brass is very forgiving to machine. If you modify an end mill to machine brass you might be the first to ever do it. Change your thinking to focus on setup. This is not a demanding task where we're outside the bounds of normal tools. Pretty much the opposite. Look for obvious problems not subtle ones here.

How far out of the vice is the rod sticking? Reduce it as much as possible.

What you may consider a light cut may be well beyond what is appropriate. Can you be more specific about your spindle rpm, radial depth, and axial depth?

Lets see pics of the action.
 
Yes, I think the tool speed is too high. But also, a slightly-dull tool usually cuts better in brass, without grabbing the work. You see this more with drills, but if the mill setup has any flex in it, you'd see it there, too. You might try stoning off some of the edge on the mill, so the edge angle isn't so acute.
 
You’ve got the spindle going at almost router speeds. But, I don’t think that’s your problem. You say the bit grabs the piece. OK, then that tells me you are climb milling. But, you say you are not? If you are running the spindle at 2,500 rpm and conventional milling brass. Then this thread on this issue/problem would not be happening. You would not be having the issue you are describing. Conventional milling would be trying to push the part away, not trying to grab it. Sorry, but you need to carefully start over and double check your spindle and feed directions again. And pics for us is a definite plus in trying to help…Good Luck, Dave.
 
There is misleading information in this thread about a certain spindle speed being too high for brass. Beginners may start associating spindle speeds with SFM, which is incorrect. The diameter of the tool must be taken into account along with rpm to determine SFM.

A 1/2" end mill at 2400 rpm is an SFM of about 314, squarely within typical brass SFM, which has a very wide SFM range depending on the tool. The problem here sounds to be rigidity and/or too big of a chip load. I really think its not wise to suggest to beginners to start dulling end mills. Thats a dark road that leads to more guessing and "alchemy" approaches to solving things instead of focusing on the basics which are the root of the problem.
 
Steve: The vice is the problem, first I would use a "V" block on its side slide in material about 1/16th more than you need. Place thin parallel aginest the material and the back of the vice tighten vice the best you can there place a "C" clamp around front and back of vice srew it down tight. Take small cuts .010 deep max very slow feed. Will work like a champ also I would use a four or six flute end mill and lower the RPM as extream RPMS generates heat very fast. Flood part with coolant the best you can. Sure hope it helps. Tom
 
4 words. Get A New Vise. Those screwless vises are OK (when they are new and work correctly) for a quick hold when drilling. They are NOT for milling. I run my cutters at 3000 rpm for brass with no problems. Brass is very easy to machine and your work should handle 2400 RPM without any problems.
 
Bruce_Mowbray said:
4 words. Get A New Vise. Those screwless vises are OK (when they are new and work correctly) for a quick hold when drilling. They are NOT for milling. I run my cutters at 3000 rpm for brass with no problems. Brass is very easy to machine and your work should handle 2400 RPM without any problems.
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You can use a screwless vise for milling, just like you can use clamp downs and no vise for milling. Its just another workholding option. The worst thing about them IMO is the inconvenience of not having a handle and having to rearrange the pin as workpiece sizes change, which are both obstacles to learning, where experimentation and rapidly trying out different things is critical. I'd avoid them just for that reason.
 
Thanks everyone for your input. I think I'll be ordering a new vise tomorrow. I think that's my primary issue at this time.
 
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