Milling bits for brass?

[Twmaster]

Been busy in my workshop today making parts for a lathe and my mill. I tried to mill some brass bar for a lathe part but kept running into problems with the mill digging in and either stalling or jerking the part out of the fixture.

I've tried slow feeds, made sure to not be 'climb milling' and have very sharp high quality tooling.

Am I forgetting the chicken giblets or something else? (Sorry Zee, no tan M&M's to offer the machine Gods.)

Been cutting steel and aluminum all day without a hitch...

So, what am I doing wrong?

 

[Tin Falcon]

Hmm brass can be a funny animal and more so if if it is actually bronze. Brass can be grabby with drill bits. I have had some brass that is a bit frustrating and other stuff that the metal jumps right off when the tool gets near it.
tin

 

[Toyman01]

Brass uses a lot less rake on the cutters. I have even used a HSS bit blank to cut brass with success. A bit that cuts steel well will grab brass and stall my lathe.

 

[steamer]

I stone a small flat on the edge of drill bits with a stone layed along the axis of the drill. Just a slight flat at the cutting edge and your grabbing days are over. I try to keep two different sets of drills, one for brass and one for everything else...but they do get mixed ;D

Dave

 

[websterz]

Lube it with peanut butter. Creamy of course.

 

[Kermit]

I stone a small flat on the edge of drill bits with a stone layed along the axis of the drill....
Dave

I think I need to know more. I'm currently getting a rect. bar of alum. bronze down to size for a valve housing on my first engine and have encountered the Grab before and expect to encounter it again unless ... :bow:

Which edge are we talking about? The side or the bottom angle. I need the 'for dummies' version as usual.

Kermit

 

[Toyman01]

Check this link:

http://www.mini-lathe.com/Mini_lathe/Tool_grinding/tool_grinding.htm

The next to the last paragraph is the relevant one.

 

[Troutsqueezer]

I am by no means an expert but the last time my mill grabbed a part and dug in, I forgot to tighten the z axis holding screw.
This is on an HF mini mill where the spindle can and does slip down. Maybe on yours that is not a problem.

 

[Twmaster]

Yo fishy dude!

Nah that's not it. My Taig mill, like your X2 does creep down if not locked. I have the lock engaged. Lots of comments on drill bits and lathe tools... Nothing about end mills...

 

[shred]

How fast are you spinning the bit and what sort of brass is it? 360? Naval? Mystery?

I've cut lots of brass on a taig and the only problem has been hanging onto it in the vise.. it can be slippery.

 

[Stan]

Unless you are using negative rake tools, brass will pull the material into the cutter. Unless the workpiece is loose in the vice, this movement comes from the backlash in the screws in the machine. One thing that helps on the mill is to tighten the lock screws tight on the two axis not being used and tighten the lock on the axis in use to the point where it is tight to turn, then don't try to hog off too much material in each pass

 

[Twmaster]

The material I've bought is supposed to be C360. I'm spinning a 5/16" 4 flute cutter at the slowest speed on the mill. (Sorry, don't really feel like looking up the pulley speed table right now)

I've tried to take lighter cuts but had similar results. I did hove one instance of the part jumping out of the vise. Of course that was because I fouled up the positioning in the vise. Totally my goof up there.

Otherwise I've got the non moving axes locked on the mill.

I am assuming a higher flute count (ie a 4 flute instead of a 2 flute) cutter would be better?

 

[Tin Falcon]

The material I've bought is supposed to be C360. I'm spinning a 5/16" 4 flute cutter at the slowest speed on the mill. (Sorry, don't really feel like looking up the pulley speed table right now)

you should be running that end mill about 2000 -3000 rpm maybe you are running you spindle too slow.
Rule of thumb try to follow calculated/published recommendations for speeds and feed. for any machine on small machines reduce the depth of cut and take more passes. Sometimes when a machine is making noise it is crying for more metal and you need to feed it.
Tin

 

[steamer]

Well, negative rake tooling would help but for the mill is somewhat out of the ordinary....at least at reasonable prices

First lets look at the basics.

Do you have a picture of the set up ?

If the vice jaw is tilting, it won't hold on well....especially to brass.

If that is the case, straping to the table may be the only option

If it goes down on the table, put some writing paper under it and block the part in to the dovetails with dowel pins

A couple of CLEAR photo's would help a lot here.

Also depending on the cut, you can augment the vice with a strap too.
Your not climb milling are you?

Dave

 

[Deanofid]

Hi Mike;
You're running the spindle too slow on your milling machine, I think. I usually run a four flute 1/4" end mill at about 2500 or better for 360 brass, and never have a problem, (Taig machine). At slower speeds, it gives the cutting side of the flutes a chance to grab and pull on the piece.
Try it running fast, and let us know if you still have problems.

Since this thread is associated with cutting brass, and drilling has been mentioned, here is how to hone your drill bits for use with brass. I posted this a while back, somewhere else on the forum, but don't remember where. This is a re-run.

This is how a stock drill bit looks on the end. It comes to a very sharp edge where the bit cuts metal (arrow). That same sharp edge that cuts steel so well will also dig in hard in brass and suck the bit into the work.

To take that sharp edge down, you run the cutting edge of the bit along a honing stone. The idea is to make it flat, which is no good for cutting steel, but cuts brass very well, and stops the grabbing problem. Run the bit in the direction of the arrow towards you, honing in only one direction. It usually takes 3-5 strokes to get the sharp edge off and condition it for brass cutting. (I realize the arrow has two heads, but hone the bit in only one direction.)

When you are done it will look like this. The shiny part you see is where the sharp edge has been honed down flat. It only takes a very small flat to be effective. No more grabbing.


On the same brass cutting subject, HSS tool bits need to have NO grinding done on the top of them for brass;

I think the pics are self explanatory, but just ask if not.
Hope this is of some use.

Dean

 

[Twmaster]

Thanks Dean. I'll try a faster speed and report my findings on the next installment of 'Brass Monkey Business'

 

[Kermit]

Since this thread is associated with cutting brass, and drilling has been mentioned, here is how to hone your drill bits for use with brass. ...Hope this is of some use.

Dean

Thank you for that answer Dean. It was the kind of explanation I needed to see and know.

Kermit

 

[Twmaster]

I am happy to report that running my cutter almost twice as fast has made a huge improvement. Thanks to all for the tips. I love this forum site!!

 

[Ancientmx]

Deanofid posted pictures of honing a bit are you still around? Can you repost? I am having trouble milling some brass also

 

[johwen]

Been busy in my workshop today making parts for a lathe and my mill. I tried to mill some brass bar for a lathe part but kept running into problems with the mill digging in and either stalling or jerking the part out of the fixture.

I've tried slow feeds, made sure to not be 'climb milling' and have very sharp high quality tooling.

Am I forgetting the chicken giblets or something else? (Sorry Zee, no tan M&M's to offer the machine Gods.)

Been cutting steel and aluminum all day without a hitch...

So, what am I doing wrong?

Hi Use a negative cutting rake for s nice machining experience and a good finish to size Works really well. Johwen