Brass Milling Parameters

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Brass Milling Parameters

Postby hanselcj » Tue Aug 12, 2014 1:35 am

I had an old post with some QnA on brass milling, but I made a lot of progress since that got started so I am making a big new post to sum up what I have learned.

Shapeoko: I am running a shapeoko 2 with Z-axis upgrade (shouldn't matter much for this), and a DW660. The spindle upgrade will probably make a big difference vs the stock shapeoko. Your mileage may vary depending on upgrades and spindle.

Material: 1/16" thick 353 engraver's brass. Works well with high speed mills like the shapeoko. 360 is supposed to be very acceptable as well, but I have yet to try it. Other brass makeups can be very tough to mill. 353 is a dream to mill; I just wish it wasn't 45 dollars a square foot!

I ran a set of parameters to try and optimize brass milling. My first set of experiments were with a 3 flute straight mill 1/16" in diameter. A single used bit performed all the experiments displayed below as well as the two dovetail gauges. I brushed all cuts with a simple cutting fluid.

First I varied the feed rates. Started with 5in/min, and finished at 11in/min. Depth 0.015" 11in/min seemed to work but had some bit wonder. I dropped back to 10in/min for the following tests.

Image

Then I increased depth from 0.015" to 0.03" 10in/min. I don't know what happened to the last one, but it appears to have milled all the way through my 1/16" plate. I double checked the Z-axis calibration and It is good.

Image

I realized at this point that I wasnt fully stressing the X axis, which should be weaker than the Y axis. I rotated the previous test 90deg and tried again. Taking the two tests into account the 0.03" might want to be avoided. 0.025" ought to be safe for hogging out material. Use 0.02" for finer detail cuts. Still 10in/min.

Image

I had cut out a dovetail gauge (right) with an initial set of guess parameters. They worked, but weren't ideal. The left gauge was cut using the new parameters and cutting fluid. It was much faster and should maintain longer bit life by taking larger bites.

Image

Next I moved on to a 1/8" double flute bit from inventables. I started with a similar test as before (X and Y movement this time), and the wheels fell off really quickly. I only had two bits from the starter pack and they both had quite a few miles on them. This is probably not a good representation of a fresh bit. 5in/min at 0.015" depth worked ok, but 7in/min at 0.02" depth was very poor. Stick with 0.015" depth, and use 5in/min speed for hogging. 4in/min would probably do well for detail work.

Image

In conclusion I would recommend the thinner bits for brass. Cutting all the extra metal takes a lot more umph than most shapeoko users will have available. Even if you need to remove a large amount of material, the smaller bit can run at twice the speed with a greater depth.

3 flute 1/16" bit:
10in/min feed rates
0.02" drop down
60% step over

2 flute 1/8" bit:
4in/min feed rates
0.015 drop down
60% stepover

Additionally I would caution against the shards that are produced by this milling. WEAR EYE PROTECTION!!! The cutting fluid helps keep it from getting kicked everywhere, but it still travels. I got a tiny shard in my hand and it was difficult to remove. Latex gloves might not be a bad idea.

I have some spiral bits of different diameter that I was thinking about trying, but the 1/16" bit is very affordable and gives excellent results. If I ever want to cut 1/2" brass, then I will readdress the issue. Until then, I am a happy camper! The only other thing to try would be engraving bits. Those are made for this sort of thing, so a similar set of feed rates and depths ought to perform really well.

-Chase
Shapeoko 2 #4951: Xbox 360 Pendant, Z-axis lead screw and NEMA23 upgrade, DW660 with Loc-Line dust collection, Googly Eyes, Swivel cutter attachment.
hanselcj
 
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Location: Central Florida (east coast)

Re: Brass Milling Parameters

Postby RobCee » Tue Aug 12, 2014 10:31 am

The best practise with brass is to use new milling cutters, as you need a very keen edge to cut it well. Once they become worn, the performance really degrades. When machining brass, I would always use a new bit, then downgrade it for other materials afterwards, where it will still perform well.
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Re: Brass Milling Parameters

Postby cvoinescu » Tue Aug 12, 2014 10:43 am

Thank you for taking the time to share this. I, for one, really appreciate it.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk
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Re: Brass Milling Parameters

Postby WillAdams » Tue Aug 12, 2014 10:53 am

It's people sharing like this, which allows us to build up the documentation on the wiki --- very, very appreciative of everyone who shares information like this.
Shapeoko 3XL #0006 w/Makita RT0701 Router w/0.125″ and ¼″ Elaire precision collets
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Re: Brass Milling Parameters

Postby hanselcj » Tue Aug 12, 2014 10:57 am

Thanks, community is what I am interested in. I set out to mill some brass and there wasn't anything in the wiki, and I didn't get a lot of feedback in the forum other than some material recommendations. Hopefully the next person can jump in with out having to use 20 bucks of brass to figure out the best mill parameters!

-Chase
Shapeoko 2 #4951: Xbox 360 Pendant, Z-axis lead screw and NEMA23 upgrade, DW660 with Loc-Line dust collection, Googly Eyes, Swivel cutter attachment.
hanselcj
 
Posts: 96
Joined: Tue Apr 01, 2014 9:57 pm
Location: Central Florida (east coast)

Re: Brass Milling Parameters

Postby hanselcj » Tue Aug 12, 2014 10:53 pm

One last thing

Image

Brass monkey. That funky monkey!

-Chase
Shapeoko 2 #4951: Xbox 360 Pendant, Z-axis lead screw and NEMA23 upgrade, DW660 with Loc-Line dust collection, Googly Eyes, Swivel cutter attachment.
hanselcj
 
Posts: 96
Joined: Tue Apr 01, 2014 9:57 pm
Location: Central Florida (east coast)


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