MY END MILL IS COLD- HOW IS THIS POSSBLE??!

[danaman]

Hey guys, I was milling some hot rolled steel on my diy cnc, my feed rate was 59 inches per minutes, 0.039 inch depth of cut, 0.60 inch radial cut, at 15,000 rpm on a 5/8" single carbide insert cutter. I am not using any water coolant, there were many sparks, many blue chips, I was expecting my insert to be destroyed... when I stopped the spindle, I felt my end mill & insert, it was cold, not even warm, it was flat out cold. How is this possible? The blue chips were extremely really hot & my work piece was warm. Is this some kind of anomaly?

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[Superman]

Is this some kind of anomaly?

No....... but that is how you would want carbide inserts to run, you may have hit the sweet spot, for that particular setup
- the idea is... that the cutting area is where the heat is generated ( this slightly softens the material at the cutting edge ).... the heat generated is in the chip, and is ejected away from the cutter body before that heat is transferred onto the insert and body...or into the stock material you are cutting
You'll have noticed that the chip will continue changing colour as the heat continues along the chip

If you altered feed or speed, you'll probably find that the heat does get transferred


Hint...... the colour coding on the insert packet is related to the colour the chip turns to after it has been cut ...... the blue being a low carbon steel, yellow for stainless steels, red for the cast irons.......
( so if the packet cutting guide shows only a yellow colour with a recommend S & F...it's not suitable for steels ) ( some makers use a letter instead of a colour ie P,M,K,N,S & H )

[ERUS]

+1

The heat is leaving with the chips. That is what you want to happen.

They have some pretty good specific coatings for running dry now. We are doing a 21" x 19" x 8.5" piece of 4140 heat treated to rC36. On all the roughing operations we are running it dry. If we try to run coolant the inserts fail very quickly.

[danaman]

Here it is cutting steel at 24,000 rpm on a 6mm end mill at 1100mm/min feed rate I felt the end mill after wards it was cool to the touch & it was just as sharp as if it had never cut anything. Isn't 24,000rpm way way faster what any feeds & speeds calculators would recommend for a 1/4" end mill? How is this possible? And why is it working?

here it is cutting some cold rolled steel

here it is cutting with a laser temp monitor on it.

[danaman]

Hmm well i guess according to this website I could be going faster
Speeds & Feeds

[ERUS]

I know a few people from Haas and Mastercam. They were playing around with feeds and speeds on dynamic toolpaths, which always cut at the same stepover and don't allow the tool to go into a corner. From what I was told, there really isn't a upper limit to the softer materials. It will cut as fast as the spindle can turn and the axes can feed it, as long as you can clear out the chips.

Were doing some aluminum with a 1/2" high helix 2 flute carbide endmill at 12,000 rpm and 6,000 mm\min (240 in\min).

[alan_3301]

I wanna see the videos. Why'd you remove them?

[danaman]

I wanna see the videos. Why'd you remove them?

Did some roughing passes with my 16mm indexable end mill (5/8inch) 5mm depth of cut axial, 4mm depth of cut radial, 560mm/min, at 15,000 rpm. This is on a 2.2kw chinese cnc 6040 router. Cutting some cold rolled steel. Dry Milling.

[danaman]

I wanna see the videos. Why'd you remove them?

Here it is milling some hardened steel, I touched it right afterwards cool to the touch wasn't even warm.,