Cutting Brass

[Dave Sheldrake]

Inverse square law follows Brass and most copper alloys.
You can cut 0.5mm brass with a 150watt CO2, add 0.1mm and you want 180 watts, a kern 400 watt will cut aluminium sheet @ 1.5mm but if you want to cut 4mm aluminium you need 2kW's, the upper limit for aluminium to get a good clean cut is 15mm plate, by then you are in silly numbers like 8kW+

[Phil Vernon]

If you have a really accurate CNC Engraver it shouldn't be an issue.
Just make sure that you don't cut right through. i.e. 2mm thick brass cut to a depth of 1.9-1.95mm so the internal part wont move. hold the brass in place with double-sided tape.
Then you have 2 options, 1. Do one final cut at slow speed and hold the parts in place...a bit dangerous as machines can make sudden movements, or 2. remove the piece (still one piece, just holding in there) and file the back of it until you file through that 0.05 mm.
I have had customers doing Elevator panels out of 1.2mm Stainless this way.
Also use Readily Machinable Brass and you may not need lubrication.

[Robert L Stewart]

If you have a really accurate CNC Engraver it shouldn't be an issue.
Just make sure that you don't cut right through. i.e. 2mm thick brass cut to a depth of 1.9-1.95mm so the internal part wont move. hold the brass in place with double-sided tape.
Then you have 2 options, 1. Do one final cut at slow speed and hold the parts in place...a bit dangerous as machines can make sudden movements, or 2. remove the piece (still one piece, just holding in there) and file the back of it until you file through that 0.05 mm.
I have had customers doing Elevator panels out of 1.2mm Stainless this way.
Also use Readily Machinable Brass and you may not need lubrication.

Thank Phil,

Your method works well when doing a few parts.20141028_201135_resized 800x600.jpg
I do a few jobs that require hand-holding a part. It is tricky especially when the part is small and fingers are only
two inches away. I only do this when edge beveling as on this .125 thick brass component (2.5" x 3.5") that I do about 100 pieces both sides.

I have learned that brass is a grabby material to mill.
I would not want to be hand holding a small piece when the cutter decides to
catch and throw it about. I love the double stick method and use it a lot but it's important to keep the tape away from cutter.

I also can not imagine filing cleanup on over a thousand pieces.

Robert

[Kev Williams]

I've been cutting 2" tall brass numbers for my competition for years, although thinner. As you said before, holding what you're cutting is the main problem. Actually, it's ALWAYS the main problem! I used to tape everything down, then spend hours removing the tape...

What I do nowadays is to create stencil cut. Below is a screenshot of part of one of my past jobs, 2" letters and numbers, to be cut with a .062" endmill. The stencil openings are .073" wide, which leaves a .011" 'bar' to keep each letter in place. Doesn't sound like much but I've found that's all I need. It's enough bar to keep the letter in place, but thin enough it's very easy to twist & break the bars to remove the pieces. Then it's just a matter of sanding the leftovers smooth with a 1" belt sander.

There's a learning curve with where the put the 'bars', the letter spacing, how big a piece of material to start with, etc., but I never use tape anymore!

[Phil Vernon]

If your doing a full sheet then a combination of the above 2, but it would probably mean to send 2 programs to the machine.
1 to cut through to within a smidge of right through (.05mm, 2 thou) then the 2nd to cut right through but leaving Tabs as Kev said.
Then twist them off and cleanup the small 0.05mm thick tabs.
Sure you are cleaning up 1000+ pieces but your keeping the work in house.

[Ross Moshinsky]

Thank Phil,

Your method works well when doing a few parts.20141028_201135_resized 800x600.jpg
I do a few jobs that require hand-holding a part. It is tricky especially when the part is small and fingers are only
two inches away. I only do this when edge beveling as on this .125 thick brass component (2.5" x 3.5") that I do about 100 pieces both sides.

I have learned that brass is a grabby material to mill.
I would not want to be hand holding a small piece when the cutter decides to
catch and throw it about. I love the double stick method and use it a lot but it's important to keep the tape away from cutter.

I also can not imagine filing cleanup on over a thousand pieces.

Robert

If I were you, I'd buy a couple of lighthouse motors (assuming you don't have a vac setup), build a simple enclosure, and build a 25"x49" vac table to sit on my existing spoil board. I'd use 1/8" MDF as the bleeder board. Break the job into 1/4 sheets of the brass and throw out the MDF bleeder board regularly. I'd also probably use my cheapo 1/8" O Flutes (or maybe even go a little smaller if the job required). You should be able to do the job that way without too much of an issue. Full depth passes with lubrication and slowish speeds should work. If you try to cut remotely fast, I'd imagine you'll have issues.

[Scott Shepherd]

Sure you are cleaning up 1000+ pieces but your keeping the work in house.

Just because you have a hammer, doesn't make everything a nail. There's no way at all that you'd ever be remotely competitive to someone cutting with with the right machine for the job.

Sure, you can do them all day long, but when someone can do more in 10 minutes than you can in 2 hours, it's an issue of working smarter, not harder.

While someone else is cutting these, I'd be running other jobs and double dipping on the profits.

[Robert L Stewart]

I've been cutting 2" tall brass numbers for my competition for years, although thinner. As you said before, holding what you're cutting is the main problem. Actually, it's ALWAYS the main problem! I used to tape everything down, then spend hours removing the tape...

What I do nowadays is to create stencil cut. Below is a screenshot of part of one of my past jobs, 2" letters and numbers, to be cut with a .062" endmill. The stencil openings are .073" wide, which leaves a .011" 'bar' to keep each letter in place. Doesn't sound like much but I've found that's all I need. It's enough bar to keep the letter in place, but thin enough it's very easy to twist & break the bars to remove the pieces. Then it's just a matter of sanding the leftovers smooth with a 1" belt sander.

There's a learning curve with where the put the 'bars', the letter spacing, how big a piece of material to start with, etc., but I never use tape anymore!

Kev,
Thanks for your reply. I have the water-jet people rough out my brass using your system, works great. Have not tried
it on the CNC yet. Any system to get away from the tape is good.

Robert

[Robert L Stewart]

If I were you, I'd buy a couple of lighthouse motors (assuming you don't have a vac setup), build a simple enclosure, and build a 25"x49" vac table to sit on my existing spoil board. I'd use 1/8" MDF as the bleeder board. Break the job into 1/4 sheets of the brass and throw out the MDF bleeder board regularly. I'd also probably use my cheapo 1/8" O Flutes (or maybe even go a little smaller if the job required). You should be able to do the job that way without too much of an issue. Full depth passes with lubrication and slowish speeds should work. If you try to cut remotely fast, I'd imagine you'll have issues.

Ross,
Thanks for the wonderful info.
I had no idea about the Lighthouse motors. Excellent thought, lots of possibilities there. I usually build a pvc vacuum pod with
O-ring for every project. I understand the concept of the enclosure just not sure how the 1/8" bleeder board works. Also what is a
1/8" O flute cutter?

[Ross Moshinsky]

Ross,
Thanks for the wonderful info.
I had no idea about the Lighthouse motors. Excellent thought, lots of possibilities there. I usually build a pvc vacuum pod with
O-ring for every project. I understand the concept of the enclosure just not sure how the 1/8" bleeder board works. Also what is a
1/8" O flute cutter?

Basically make a table like this: https://www.youtube.com/watch?v=fOrkvPF0pro

The 1/8" MDF bleeder board is simply a piece of 1/8" MDF that the vacuum sucks through. My experience with cutting small letters is that once your bleeder/spoilboard is anything but flat, you can start getting problems. By using 1/8" MDF, you can constantly change spoil board for a low cost.

1/8" O flute is a type of endmill typically recommended for plastics and soft metals.