Need Help!- Aluminum alloy plate that machines easily

[Dan.antes]

I tried to machine some 3003 aluminum 1/4" plate. I have a HSD high frequency spindle. I tried RPM's from 10k to 16k and feed rates of 30-120 IPM width depths of each cut from .035 to .085. Any way I went at it with a 3/8" o flute bit the cut line and edge chip welded and made a real mess. I originally made samples with plate scraps that machined easily. I have no idea what alloy they were. Can anyone recommend an alloy that is easy to machine with a high frequency spindle? This material is not structural only decorative. What tool, feeds and speeds should I use? Thanks

[Geof]

The least expensive aluminum alloy that machines nicely is 6061 T651. With carbide tooling you can run at 1000 feet per minute or more. Coolant or lubricant is almost essential to get the best finish. You must be using a router so the least messy way would be to simply brush onto the plate either a water miscible coolant, without water, such as the Blaser stuff or Shell Dromus B which is what we use. Alternatively you can use automatic transmission fluid, strange though that may seem. keep you depth of cut shallow when you are only brushing on coolant; shallow being not more than 0.05". For tooling find a supplier of high helix two flute micrograin carbide toolbiuts, Garr is one.

[Dan.antes]

I got the 6061-T651. Cut like butter with my 1/4" o flute for aluminum by Amana Tool. I cut at 150 IPM .0625" per pass to a final depth of .245 leaving a .005 onion skin so I could hold down with my vacuum pump. RPM at 12500. I had none of the problems that I had with the 3003 plate. I did take the 3003 plate to a waterjet company so they could cut it for another project I have to save a little money on the 6061-t651. The 6061-T651 was over twice the cost of the 3003. I paid $350 for a 4x8ft x 1/4" sheet. Anyway, I am through the project and am confident I could cut aluminum again. Thanks Geof!!!!

[Geof]

Originally Posted by Dan.antes I got the 6061-T651.... I cut at 150 IPM .0625" per pass to a final depth of .245 leaving a .005 onion skin so I could hold down with my vacuum pump. RPM at 12500.......

Good to hear things went well.

If you have that rpm with the aluminum cutter using a coolant mister spraying right on the cutting area you may be able to double your cutting depth. Time is money and if you take half the time on a fixed price job you are making more money; I doubt know about you but to me that is attractive.

[Dan.antes]

Geoff,

I am worried about using anything other than air as coolant. I have a dry vane vacuum pump and I am told that even the smallest amount of coolant with toast the cabon vanes. This was a one off job for Indiana Universtiy. Even baby sitting the tool with a air chuck to cool it and starting with the wrong material , I made good $$$. Thanks for your help!!!! I plan to pursue a lot more of the oddball jobs like this so I am sure we will get a chance to chat agan soon. Best regards:>>>

[Geof]

Originally Posted by Dan.antes Geoff, I am worried about using anything other than air as coolant. I have a dry vane vacuum pump and I am told that even the smallest amount of coolant with toast the cabon vanes....

This does not seem logical given that the vanes are graphite; they have to be considering the only other carbon alternative with adequate stiffness is diamond.

I have two suggestions:

First: Seek out other opinions on the susceptibility of dry vane vacuum pumps to organic contaminants; I really cannot understand that warning. I can see it with oil filled pumps because you could generate a horrible sludge if the oil got contaminated.

Second: If you have a good high dollar project in the offing build yourself a cheap vacuum pump that will not be worried by a bit of coolant vapor; here is a description showing how to do it:

http://www.cnczone.com/forums/showthread.php?t=53796

[LaserImage]

Originally Posted by Geof This does not seem logical given that the vanes are graphite; they have to be considering the only other carbon alternative with adequate stiffness is diamond.

You would be amazed at just how fragile those vanes are. I had a couple of very small pieces of metal shavings get into the vacuum system in my airplane - the pump went "poof", all the vanes shattered. I don't know if they are the same type as you are talking about, but I think they are.

G

[Geof]

Originally Posted by LaserImage You would be amazed at just how fragile those vanes are....G

I know how vulnerable they are to mechanical contaminants, they need good filters on the intake side. It is the claimed vulnerability to fluids or vapors that I don't fully understand. Of course a large volume would probably shatter the vanes because it is not compressible but that can be avoided with a trap.