milling brass

[outsider347]

I am about to purchase a center cutting end mill to machine brass.
Should I use a 2 flut end mill?
tks

 

[Rapscallion]

You mean "over-center-cutting". "Over-center-cutting" means that you can plunge with it because of its geometry at the center of its flat bottom which has sharp edges. These are more often referred to as slot-drills (at least here in ZA). Whereas end mills have a hollow geometry at the center of their flat bottom and can not plunge very deep thus they are more commonly used for cutting the "ends" of material and not plunging through the top.

Brass is relatively soft and the cutting forces are not that high so I don't think the amount of flutes that you use will be much of a factor. If you want less side force (push-away) on the cutter then use more flutes it will tend to cut more and be less bumpy but, if you are cutting at high spindle speeds then the order is reversed as more flutes will tend to have a rub, rather than a cut effect.

I find three flutes with over-center-cutting to be a happy medium in most cases.

Hope this helps.

 

[mwooten]

That was a very good explanation! Good learning point for me.


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[chuckorlando]

Keep in mind that the number of teeth effects the feed as well. 2 flutes will be a pretty slow feed for a decent finish. At least the experience I have had on alum with 2 flutes.

 

[Terrywerm]

You mean "over-center-cutting". "Over-center-cutting" means that you can plunge with it because of its geometry at the center of its flat bottom which has sharp edges. These are more often referred to as slot-drills (at least here in ZA). Whereas end mills have a hollow geometry at the center of their flat bottom and can not plunge very deep thus they are more commonly used for cutting the "ends" of material and not plunging through the top.

Very nice explanation, and thank you! I had this pic here, so thought I would add it.



I would like point out that this is a classic example of how terminology can vary from place to place. Here in the U.S., "center cutting end mill" is the common term, and "slot drill" is seldom heard on this side of the pond. None of the terms used in this thread have been incorrect. It is good to remember that there may be minor differences in terminology from place to place and that we all have to be respectful of those differences.

 

[outsider347]

Thanks very much for the quick responses Gents.

ed

 

[Rapscallion]

I would like point out that this is a classic example of how terminology can vary from place to place. Here in the U.S., "center cutting end mill" is the common term, and "slot drill" is seldom heard on this side of the pond. None of the terms used in this thread have been incorrect. It is good to remember that there may be minor differences in terminology from place to place and that we all have to be respectful of those differences.

Thanks for pointing that out Terrywerm. :thanks:

 

[KMoffett]

Never seen an end mill specifically ground for brass, but the drills I use on brass (and Plexiglas) have the cutting lip ground off, parallel to the axis. This results in a "scraping" action rather than a "shearing" action.

Ken

 

[Andre]

Never seen an end mill specifically ground for brass, but the drills I use on brass (and Plexiglas) have the cutting lip ground off, parallel to the axis. This results in a "scraping" action rather than a "shearing" action.

Ken

I have had phosphor bronze bushings grab and auto feed in a drill press. Drilling out a bushing in a 5lb drill press vise, slow speed (bit NOT modified for brass) It was fine for a second, then it lifted the heavy vise off the table and auto fed towards the chuck. Drilled right through in almost half a second. Very scary, be careful!


Like this: (not my video, from Tom Griffin here on HBM)

[video=youtube;8Ri6poVpQM8]https://www.youtube.com/watch?v=8Ri6poVpQM8[/video]

 

[Mid Day Machining]

I am about to purchase a center cutting end mill to machine brass.
Should I use a 2 flut end mill?
tks

For a good answer to your question we need a lot more information than you've provided.

What is the configuration of your part? How much material are you going to remove? And the bIg question, HOW RIGID IS YOUR MACHINE?

If you plan on cutting a pocket, drill a starter hole first. Brass doesn't do well when you plunge with an end mill on most of the machines hobbyists use, and that's not meant to be a put down. I have seen some expensive CNC machines than didn't do well machining brass. A lot of the problem there was programmer error.

While brass is a pretty soft material, if you don't have experience machining it, you can have a lot of problems When I machine brass, I do it dry. The only time I use lubrication I use is when I drill small holes or tap any size hole.