Speeds and Feeds

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Brento

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Hi all, so im sure this question is commonly asked by hobby machinist all around. When i started machining i did it by sound and feel (mainly bc i hand fed on a lagun mill). Now as i am getting more and more experince i am understanding the formulas on how to find your speed and your feed. However the one bit of information i am curious about is what is a good sfm and chipload to start out with. This question is also good to know for my job as well. I am cutting Aluminum and steel most of the time but sometimes stainless and titanium. Also same question but for drills and reamers would be great as well!

As a secondary question would you sfm change using carbide vs hss? Ive been told you can double your feed/speed when going from hss and carbide.

Thank you guys for your time in advance.
 
I try to aim at .001 per tooth, any cutting material. Aluminum or steel. (on a mill, lathes are different.) I was 'raised' on HSS, so carbide is a foreign land as far as speed is concerned. Your results may vary.
 
Depends do you have a cnc? On a 3/8 3fl carbide endmill in aluminum give it .15 stepover up to .625 depth of cut with 6000rpms at around 70ipm or about .004 feed per tooth.

1/4 3fl carbide in aluminum 6000rpm .1 stepover up to .5 depth of cut around 40ipm or .002 feed per tooth.

That’s on an older cnc I would not try those numbers on a manual. Of course also using high quality is made endmills.
 
A lot of it will depend on the tool and the machine. There are also other factors such as workholding and tool holding. There a cases where the workholding isn't as secure as it could be and speeds and feeds need to be adjusted. There are also factors such as finishing vs roughing, coolant, etc etc.

You can find a lot of information from the manufacturers of the tools. But carbide will be able to take a lot more SFM than HSS will. In most cases, the SFM for aluminum will not be obtainable on hobby mills, so I usually give it all the RPMs I have, take at least .001 IPT and see where that gets me. Sometimes I need to back it off a little bit on speed, but try to avoid going below .001 IPT. An example from Harvey tool, they recommend 800-1500 SFM for their tools in 6061 aluminum. With a 3/8" end mill, that is 8150 to 15280 RPM. You probably won't get that with most machines. With a 3 flute end mill, the lower SFM and .001 IPT, you need to feed 24.5 IPM. If you don't have CNC, or at least a power feed, that will be tough to get to.

But yes, you will probably want to change SFM between carbide and HSS. I hope everything I said made sense and at least some of it is helpful.
 
General rule I use is D/100 for the feed per tooth. So if I'm using a 3/8" end mill I start with .003-.004" ipt. The speed depends on the tool material and the work material.

I highly recommend that you try FSWizard. (https://fswizard.com/#) You input the material, your cutter properties, cut width and depth. It will tell you what the ideal feeds and speeds for your cut are. On my little G0704 CNC conversion I started out using 50-60% of his feeds. These days I use 80-90% of his recommended feed. On my machine 1.5 cubic inches per minute in aluminum is a the upper limit on MRR. So I try to keep my cuts below that mark.
 
Everything is making sense guys thanks. Does anyone have a suggest standard sfm to start with and then obviously massage it to the conditions in the work area?
 
My little PM25 has variable speed and feed. If I have enough cut to play with, I tweak both until it 'sounds' right. However, this comes with experience, so take it easy.

Edit: fix typos
 
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