Just broke *TWO* 1/16" end mills...

[geneb]

The first one I broke at 12,000 RPM @ 1in/sec and the second was at 12,000 RPM @ .3in/sec.

I'm cutting .062 6061 plate. Can someone recommend the correct feed & speed before I break any more of them experimenting?

(I forgot to mention that the pass depth was 0.0156)

Thanks all!

g.

[mcphill]

How long is the .062 diameter length of the tool? How many flutes? How deep are you cutting per pass?

Originally Posted by geneb The first one I broke at 12,000 RPM @ 1in/sec and the second was at 12,000 RPM @ .3in/sec. I'm cutting .062 6061 plate. Can someone recommend the correct feed & speed before I break any more of them experimenting? Thanks all! g.

[geneb]

Pass depth is .0156, cutting length (was) .25, 2 flute upshear.

tnx!

g.

[HawkJET]

What kind of machine? Any coolant/lubricant? Do you mean in/sec or in/min?

[geneb]

Originally Posted by HawkJET What kind of machine? Any coolant/lubricant? Do you mean in/sec or in/min?

ShopBot PRT 96 Alpha. Air jet coolant and I do mean in/sec, just like I wrote.

tnx!

g.

[hoss2006]

Originally Posted by geneb ShopBot PRT 96 Alpha. Air jet coolant and I do mean in/sec, just like I wrote. tnx! g.

slow that feedrate down a ton, 5 IPM or less.
Hoss

[HimyKabibble]

Originally Posted by geneb The first one I broke at 12,000 RPM @ 1in/sec and the second was at 12,000 RPM @ .3in/sec. I'm cutting .062 6061 plate. Can someone recommend the correct feed & speed before I break any more of them experimenting? (I forgot to mention that the pass depth was 0.0156) Thanks all! g.

1 in/sec is CRAZY fast! Something like 3 in/min would be more like it. You'll need LOTS of air, and preferably some coolant. You MUST keep the chips away from the cutter. At those speeds, your runout must also be very low. Those little ones break real easy....

Regards,
Ray L.

[SScnc]

I've been running 1/16" em's at 3 IPM with a plunge of 2 IPM.

I run 3/64" em's at 1.2 IPM with a plunge of 1 IPM. Both are carbide 2 flute cutting 6061 on an X2 with flood coolant. I haven't broken a bit in a long time now and I've only got ~4600 RPM.

Takes quite a while to get the job done but the details look very good.

HTH

Oh yeah, DOC for the 1/16" is 0.02" and for the 3/64" is 0.01"

[geneb]

Thanks guys. I'm so used to doing things in wood with 1/4"+ bits, my brain defaults to "in/sec" when creating tool paths.

g.

[LeeWay]

I cut that same material on my mill. I was using a trim router mounted on it, but now that I have upped my spindle speed to 6600 RPM, I get good results with a 3/16" 4 flute EM. I go .025" depth at 30 IPM @ 6600 RPM.

I was using a 1/4" bit in my trim router. My mill is set up to run automatically though, so I prefer to use it now. Here is a video of the way did it with my trim router. Turn the sound down.

YouTube - Milling aluminum sheet

YouTube - Milling aluminum sheet

[geneb]

Very nice Lee. I just discovered that my 'bot has a "default" slowest speed of .5in/sec. I'll need to change that before I run the file again.

I needed to use the 1/16" bit because of some very small features on the part - it's the mounting plate for the IFF panel in my F-15C flight simulator (http://www.f15sim.com)

Now that I know what's going on, I won't snap any more tiny cutters.

I'm tempted to use the 1/32" cutter I have if I can get the 'bot slowed down enough.

g.

[LeeWay]

With the tiny cutters, you really have to go slow. I use 1/8" cutters on 6061 bar stock and it works great. I rarely ever break an EM. I do use a feedrate of 25 IPM on those @ 6600 RPM with .02 DOC. Coolant is a must going like this though.Otherwise the flutes will clog.

Using a router, you can get away with spraying WD40 on the part. Keep the DOC and feedrate down and you should have no breakage.