Too fast or too slow?

Agree with others about using a rougher and feed being too slow. If it were me, I would run that carbide cutter around 1300 rpm and .250 DOC. Feed would be whatever felt comfortable and produced good chips. In general, I run carbide at about twice the speed of HSS. I'm not on the clock and the cutters come out of my pocket. It's fun to see how far you can push it, less so when it's your dime.
 
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33 ipm is not practical at 3/8 doc... ever watch cnc, they go fast, but with much lighter cuts, and keep repeating.
1/16 to 1/8" cuts at 33ipm ... doable
 
walterwoj said:
I don't think I understand the whole feed per tooth deal. It's prolly just me but while I think my power feed could do closer to 30 ipm I would never dare go that fast, the table would be flying! I can't help but think that if anything went wrong I would have something embedded in my face!

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You want a certain amount of chip per tooth to maintain a proper cut. Your feed is limited by available rigidity. If you cannot run 33 ipm then slow down your feed to a comfortable pace and rework the rpm so you maintain your chip load. Run your calculator with 1000 rpm or your closest speed to that and watch your feed speed drop proportionately.

Slotting is hard so go a bit less depth
 
If it were me, I would rough drill out the majority of the stock, Using flood coolant. Then I would use a T-15 or M-42 grade end mill to rough out at .100” depth of cut per pass down to .03” off final depth. Finish off the sides, (conventional cut), and bottom. .002 chip per tooth, not knowing the hardness I would probably say 80 sfpm, (factory heat treat / RC 28).
 
So I checked my power feed with a stopwatch and the DRO. It WILL do 30 ipm so the question is would anyone here run their mill table at that speed at any DOC? Am I just wussing out?

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walterwoj said:
So I checked my power feed with a stopwatch and the DRO. It WILL do 30 ipm so the question is would anyone here run their mill table at that speed at any DOC? Am I just wussing out?

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Your mill will let you know. I would never consider 3/8 deep slotting in steel at 33 ipm. Too much flex in my light knee mill.

I would happily take a side climb cut 1/2 the cutter diameter and 3/8" deep at 21 ipm with 1750 rpm.

At 1/2 the cutter diameter your primary forces are no longer pulling the material into the cut. The forces are perpendicular to the feed and tapering off to nothing as the edge moves through the cut.
 
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Walter,

I don’t know if I have all the parameters of your setup correct for sure, but I ran the LMS speed and feed calculator and got different results than you did.

Alloy steel (4140) work piece
1/2” carbide endmill
DOC was not an input parameter

Recommended spindle speed 1720 rpm
Chip load 0.003 in/flute
Feed rate 21 ipm for 4 flute endmill, 10 ipm for 2 flute endmill

Did I get some inputs wrong?

Tom
 
Inferno said:
Were you using any lubricant?
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Why would you want a lubricant?

OP, your spindle speed was insanely fast, like by a factor of 8-10 and that depth of cut..... :oops:

There is no reason to turn your cutter that fast as you will NEVER achieve the setup, rigidity or horsepower needed for the chart speeds.

Chuck the chart, it gives "examples" (Read suggestions) of proper practices under ideal conditions. Its meant for production shop with ideal conditions and unlimited tooling budgets.

.030 depth of cut along with 350-400 spindle speed with a HSS endmill would have done ten times the amount of "finished" work before getting slightly dull. And your slot would clean up very well taking .005 per side as a clean up pass.

That.....Slot? you made will not clean up anywhere near the cutter diameter, if its even straight to begin with.
 
For any close slotting I use 3 flutes mills . No overcut .
 
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