Spindle speeds question

SBranson

SBranson

Joined
Oct 29, 2006
Messages
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I recently picked up a Grizzly MiniMill used and am starting to have some fun with it.


Is there a good site with recommendations on spindle speeds for different materials?
I got the minimill because of the cost and for now I mostly need it for cutting slots in guard/spacer/ferrule type applications. I am using 416SS, copper, bronze, mild steel and wrought iron. I basically run the thing in the slow half and then turn the dial to about 500-800. I am doing light passes and pretty slow feed rate but I'm cranking by hand so I'm not sure how slow or fast I am going.

I accidentally posted this in the Custom section but got some responses saying to crank up the speed.

Btw, the speed settings on the mill has a slow range from 0-1100 and a fast range from 0-2500.
 
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Thanks John. I have some HSS and Cobalt bits but a supplier comes by work weekly so I'll get some carbide ones off of him.

Don't really understand Ochs' chart. :confused:

The one you provided has speed per tooth so does that mean multiply by 4 if I have a 4 flute end mill? I really am new to this.. I'm a woodworker.:p
 
Stuart,

Hopefully, Nathan will chime in, but the speeds per tooth in the first chart are for feed.

A rule of thumb for RPM is: cutting speed(SFM)x 4, divided by end mill diameter.

Using the SFM speeds for carbide end mills from the first chart, the speeds are going to be higher than your mill runs.

That's what folks are meaning by running up the speeds.

I have a micro-mill that runs up to 10,000, and i'm cutting damascus and 416 SS at 4300 with 1/8 inch carbide 4-flutes, and not even burning the chips.

( However, I'm a woodworker, too)

John
 
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For a point of reference, 1/4 inch HSS cutting mild steel spindle speed can be up to about 1600 rpm. For carbide endmills you can double it. If you are cutting SS or alloy steel cut your speeds in half. These are just estimated speeds since all steel is different. I normally start about 1200 rpm for the 1/4 and turn it up if it sounds good. You can extrapolate the 1600rpm for other size endmills, 1/2=800rpm 1/8=3200rpm. Like John mentioned most mills do not go that high so you cut at whatever speed works best.

One thing about cutting with the different type of endmills, HSS and cobalt, you do not want any color in your chips at all and use a really good cutting oil. For carbide, they like to be run hard brown and even blue color in the chip is ok. If it glows red its too fast. I normally do not run them at that high of a speed but they do work well running hard. Be prepared to burn up a few. Good luck
 
if you use carbide, when you are milling use air on the end mill as you are cutting, it reduces heat and clears out the shavings. plus you don't have the thermal shock you get with coolant, and the horrible smell of cutting oil. should work well with 416, coolant is always best with 300 series
 
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