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- Feb 26, 2014
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- 257
One rule for stainless. ABC - Always Be Cutting
Thanks for the write-up! I just got back from my metal supplier, looks like most aluminum is 6061, Steel is A-36, and stainless is 304. Looks like I need to slow way down.Danny, congrats on the new mill! Always cool to have a new machine.
There are a few things about milling stainless steel that you need to be aware of.
I am attaching a speed and feed chart from Niagara Cutter for stainless steel. Have a look and view it in light of what I said above. Hope it helps.
- The particular alloy series you're working with matters. There are Austenitic (200 and 300 series) and Martensitic (400 series) stainless steels and they have different machining characteristics, among many other differences. The most common SS used is the 300 series and of those, 303 has sulfur and is the easiest to machine. 304 and 316 and their variants are harder to machine and work harden much more readily. SO, you have to know what you're cutting.
- The kind of cut you're making matters - slotting or profiling. Speeds and feeds vary with each. Moreover, the number of flutes on your end mill will vary with which kind of operation you're doing. For slotting, a 2-3 flute end mill is preferred due to better chip clearance, while for profiling a 4 flute end mill will usually work better in most steels.
- There are two parameters you need to be concerned with to find the speeds and feeds you need with a MANUAL MILL: The axial depth of cut and the radial depth of cut. Axial depth of cut refers to how much of the flute length you're using and radial refers to how much of the diameter of the cutter you're using. Your speeds and feeds will vary with both of these parameters.
- Austenitic SS will work harden if you do not keep the cutter moving. The reason for this is because unlike most steels that get rid of heat in the chips that come off in a cut, SS tends to retain heat. Much of the heat remains in the cutter and most of the rest of the heat remains in the work piece. If the work piece gets too hot, it will work harden and you must cut under this hardened layer to machine it further. 303 tends not to work harden nearly as much as the other 300 series alloys, which is why it is preferred for manual machining. However, if you have sharp tools, use coolant or cutting fluid, take cuts that your machine can handle while it moves along in the cut at an adequate feed rate then all the SS types can be cut with a manual machine.
Oh, and no, you will not be running at 2500 rpm ...