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hello guys,
can anyone help me in getting the best or recommende speed and feed rate for our shell mill. we normally use it on mild steel material 1.375 thickness.
is it ok not to put a pre-hole prior to shell milling? sorry about that i am new in this kind of process.
OK, What kinda machine
Brand of shellmill
Size of shellmill
coolant/ no coolant
NEVER PLUNGE with a facemill/shellmill, you can ramp or helix with a large radius.
our sheel mills are from sandvik 2" diameter with 3 teeth and 3" diameter shell mill with 5 teeth. we usually use coolant on everything that we do. and i am using shell mill on helical milling.
I would run a carbide tipped shell mill in mild steel at about 300-400 sfpm to start off. Feedrate of about .004 ipf. Hss or cobalt at about 100 sfpm
Speed effects insert life more than feed. If your inserts or hss are lasting you can bump up the speed and increase the feed by same percentage so that the feedrate is kept at .004 ipf. If you have the available horsepower you can increase the feed rate until you get scared.
Always use coolant with HSS. There are pros and cons to using coolant on carbide shell or face mills. Some people claim the coolant causes the hot carbide to fracture as it cools to quickly and the steel chips are weaker if they are allowed to get hot. I usually run carbide face mills dry with air blast.
These cutters usually don't plunge very well or very far, depending on the insert and body geometry, you can ramp but be careful that you don't hit the center inside of the cutter.
If you are doing face milling of steel, its usually recommended that you overlap the cutter on the material by 60% of the diameter. That means 40% of the cutter is hanging out of the material. Always climb mill whenever possible, use an airblast to remove chips.
My G-Wizard feeds and speeds calculator is pretty close to what Chrliev recommends. For your 3" x 5 insert face mill, carbide inserts, I get:
420 SFM
500 rpm
0.006" IPT
16 IPM feedrate
I've run my face mills at these speeds with an air blast (no coolant), and they've worked fine even with more than 60% stepover.
Cheers,
BW