Holding down aluminum

[mccoy178]

Hello,
I'm a high school Tech Ed teacher and I can't figure out how to hold down aluminum to cut it. I want to cut 1/8" aluminum and 1/2" for two different projects. I have never had success holding down aluminum in the past but I believe I had my cut speeds wrong.

Here is my setup: We have a PRT Alpha 120. I am using 3/4" mdf as the base and I do have compressed air available. I do have a two fluted aluminum cutting bit, but we've never used it. I plan on cutting at .05" per pass at 10k rpm, but I don't know how fast to cut.


What specifically can I use to hold the aluminum down so that the inside parts don't "jump" up? I've heard guys using epoxy, but what kind? What am I securing it to? mdf? plywood?

Do I want a soft aluminum like 5025 or something hard like 2025?
I searched the forum for answers and I know they've been asked a bunch, but I'll be danged if I can find what I'm looking for.

Thank you so much for your help, as this one has me stumped.

[Gary Campbell]

Ben...
I am sure that I am not typical, but here is how I do it. I use a 3/4 MDF platten that is located by my pins and is (sealed on the back) held by vacuum.

For 1/4 and under I do the following:
soak MDF with WD40 (gallon & sprayer not aerosol)
Drill holes in the corners and locate to Vcarved index marks on platten. Screw down
Slather surface with WD40
Now I drill my holes in my part (I usually have these)
Install more screws in part
More WD40
My profiles are cut full depth +.060, .125ips plunge .75 ips move 8-12K rpm Single O flute Belin 1/4"

For thicker materials I use a .050-.060 perpass strategy. Same rpm, faster move speed. Usually takes some fine tuning

I usually have been cutting 6061, other alloys need adjustment

[Gary Campbell]

Heres a couple pieces from my shop built ATC carousel

[Gary Campbell]

Sorry about the multiple posts. Here are some 3/16 6061 drill brackets

[mccoy178]

Thanks Gary! I used screws but still had hold down issues in open areas. Do you use any type of epoxy or anything?

Some good news is that I was able to get a couple letters out that were about 8"'s tall. The material is .08" thick. No issues cutting other than hold down away from the screws.

[knight_toolworks]

I glue or screw the material down and use tabs to hold the parts in place if I can't screw them.

[mccoy178]

Steve,
What kind of glue do you use? Is there a certain thing I'd be looking for that will be easy to remove from the aluminum?

[knight_toolworks]

3m spray adhesive works well. keeps the sheet in place but not the parts. well it may depending on the size and how much heat you generate. but it is easier then screws and only need some paint thinner to remove the residue. epoxy works but you need to heat the part up with a heat gun to release it.
I found with the spray you need time or pressure to make it set well. I through it in a vacuum bag for a bit or leave it overnight.

[shoeshine]

Hey Ben, I dont do a lot of alum, but I cut a ton of brass.

If your z is dialed in, I find that you can leave tabs that are almost like foil. down to .002 -.003 will keep small parts in place and then be easily cut out with a utility knife. Just make sure there is a tab on each side of a part. they have plenty of lateral strength but if they bend they fail.

Just my $.02
Chris

[majohnson]

For my mill I use Mitee Bite Clamps. They offer several different products, I think you'll find something to work.

[itamarj]

I use those setting:

onsrud 65-010
10,000
0.3 ips
about 0.02 stepdown

I use only vacuum to hold the piece down, but only cut small pieces so it worked very well.

I wanted to ask, is it possible to cut any aluminum, or only the soft alloy one (that the only one that I had experience with).
thanks!

[oddcoach]

i also use the mitee bite clamps. I make a pocket for the part to sit in. this works well if you have multiple parts to do. I have been using rubbing alcohol as a cutting fluid. It keeps the bit very cool and does not make a mess like oils do. the bit is usually colder than when it started when the cut is done.
John

[MogulTx]

I have cut some soft aluminums and the harder, tempered alloys. Aluminum can be cut. You just need to take small cuts. You'll have to check to see what your bit and set up can do.