Help with speedds and feeds for aluminum

I'm pretty new to milling and I'm trying to double check my feeds and speeds calculations.

Can someone tell me if the following speeds and feeds are within acceptable ranges with regards to load and safety for a 1 1/2 hp 2J varispeed head bridgeport?

I looked it up in Machinery's handbook and as far as I can tell the feed rate might be slow but the RPMs look fine. But I'm worried I might be missing something.

Cutter = shell mill plain carbide inserts Cutter diameter = 3 inches Number of teeth = 6 Material = 7075 aluminum 1.5 inch wide Width of cut = 1.5 inches centered on cutter Depth of cut = .1 SFPM = 942 RPM = 1200 Feed per tooth = 0.0021 Feedrate = 15 ipm Thanks, Paul

Reply to
randomchaos
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for garden variety non-coated aluminum, I tend to keep from 400 to 600 fpm

I know that the charts show that carbide can far exceed that range, but practical experience has shown that much beyond 600fpm, you can experience fusing of the alum to the cutter.

Play with it and see what works for you.

Reply to
Jon

So you don't think that 1200 RPM is too much for the mill or safety wise? I'm a beginner and want to make sure I don't ruin the machine. Thanks, paul

Reply to
randomchaos

Normally, I'd use a much higher feed per tooth, and maybe half the depth of cut. That may be personal preference, and also may be based on how securely you can hold the work. You don't want it thrown across the shop at 1000 FPM!

You want to avoid having ALL the cutter teeth out of the work at the same time. This will cause horrible vibration. If you have to put the work a bit to one side of the cutter, this may help in that situation. (I'm not sure you'd have that problem on this setup, though.)

Jon

Reply to
Jon Elson

Do you have flood coolant? I'd think that would be a big help in keeping the work cool. If the workpiece gets hot, you can have a great big mess all over the carbide inserts! If you don't have flood, you can try mist, or even spraying something from a pump-type spray bottle. When the chips are sizzling as they come off, you know you are really removing heat from the work.

Jon

Reply to
Jon Elson

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