Are Tiny End Mills Impossible to Use in Steel?

[Chips O'Toole]

A few years back, I found a mysterious piece of steel in a warehouse a tenant had abandoned, and I eventually decided to turn it into a bench block. Today I put a v-groove in it, using a drill mill. I did not want to stress the tip of the drill mill, so I cut a slot deeper than the groove. I used a 1/8" end mill. It was Chinese HSS from Enco.

I ran the mill at around 3200 RPM, and I took cuts 0.050" deep. I moved it as slowly as I could to avoid putting pressure on it. I used a blow gun to keep chips from accumulating in front of it. It eventually snapped anyway. I tried a 1/16" mill, but it also snapped. I finished the job with a 3/16" mill.

I'm starting to wonder if there is any point in buying end mills under 3/16". So far, I have snapped two 1/8" mills and one 1/16" mill. Are these things just too weak for manual milling in steel?

 

[JimDawson]

Small end mills require a steady hand and a rigid machine. But it can be done, I have used endmills down to 1mm (0.039'') in stainless steel. But I have never tried slotting with a full width cut with a small endmill, might be OK with a 1/2 dia DOC. It could be that you were feeding too slow and dulled the endmill due to rubbing rather than cutting.

 

[tq60]

They need to spin real fast.

The tooth being real tiny takes tiny chip so the feed by hand needs to be such to feed not as fast as the cutter can clear the material.

Flood coolant to insure heat removed and as fast as the machine can go.

These are dremmel bit sized tools...

With a dremmel your hand pressure limits tool and the tool does its job.

The mill has more pressure than tool can stand so tool snaps.

Feed rate is critical as to much and bad things happen.
Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[mmcmdl]

Could you have used a saw cutter on an arbor ?

 

[Mitch Alsup]

I try not to use end mills smaller than 3/8"

 

[darkzero]

The smallest end mill I own is 1/16". I have only ever used that small once. My mill doesn't spin fast enough, about 2000 rpm max. I tried it anyway & only tried it cause I didn't have any good slitting saws at the time.

CR1018, I took baby DOCs cause I was afraid it was going to snap & because it was a 4-flute (all I had) but it got the job done. It's a Niagara end mill. I'll never try that again now that I have more slitting saws. I do use 1/16" ball end mills from time to time but only for making shallow grooves.

 

[pdentrem]

Rigidity of the machine, coolant, lots of rpm and proper feed rate to get the right tooth load. Also when cutting slots, a 2 flute is better than 4 flute. I regularly use 0.020” and 0.012” end mills. 60k rpm and between 30-40 ipm most of the time.
Pierre

 

[mmcmdl]

If you ever need to run these smaller end mills and don't have the rpms available , clamp up a die grinder on your quill . That's an old trick .

 

[darkzero]

If you ever need to run these smaller end mills and don't have the rpms available , clamp up a die grinder on your quill . That's an old trick .

I knew a machinist on another forum who made a bracket to attach to the quill on his RF-31 to mount a high speed spindle motor. I always like that idea and wanted to do something similar but I rarely have a need to use tiny endmills.

 

[mmcmdl]

I made a few , one for a Precise 80,000 rpm electric die grinder and one for my little Dotco air grinder . Worked quite well . I had an attachment for the Dotco that I used on the cnc lathe as a 4rth axis . We were developing heart pump impellers for Johns Hopkins .