Milling steel chip colar?

[Rich05]

Right now they are shiny on one side bluish grey other. Only running at 550 rpm with slow feed and .1-.05 depth cut, usinng carbide 1/2 endmill, mild steel.

If I turn down rpm it seems too slow. Am I still burning my tools up? Should the chips be shiny on both sides? I have lots of flood coolant on the part while cuttinng.

Thanks R.

[Gary55Ford]

Have you tried a 4 flute roughing end mill?

[Rich05]

I dont think have the horsepower for roughing tools 3hp

[Geof]

Originally Posted by Rich05 Right now they are shiny on one side bluish grey other. Only running at 550 rpm with slow feed and .1-.05 depth cut, usinng carbide 1/2 endmill, mild steel.... Thanks R.

Nothing wrong with blue chips, see the picture.

But you cannot do this with a half inch end mill; I was using a small face mill.

However your speed is much too low: Machining mild steel with carbide you can run at 400 feet per minute (that is the peripheral speed on the cutter; dia x pi divide by 12); this is about 3000 rpm for a half inch cutter. Some people might even suggest going higher but I am a bit conservative, I might even go down to 2500 rpm.

Using flood coolant when machining steel can be good or bad; if it is truly flood so the cutter is always thoroughly drenched in coolant that can be okay, but if the cutter is only covered intermittently with coolant it is not good because the cutting edge gets hot and then chilled with coolant and carbide does not like this. It can lead to thermal fracturing of the edge and early tool failure.

You need to try some experiments running dry, or preferably with an air blast on the tool. Start at something like 2000 rpm with a feed of 0.002" per tooth; this would be 16 ipm for a four flute cutter. Keep your depth at 0.1 or even more; sometimes when you go with a very small doc, especially with a slow feed, the very tip of the cutter overheats because the chip is too small to carry away the heat.

[Gary55Ford]

I have 4 3hp knee mills where I work and we use upto 3/4 roughing endmills on them with no drouble

[msomerville]

The fine tooth roughers require less horsepower than your conventional cutter. Like Geof said crank up your rpms and feed.

[KyleH2]

Just seconding that you're going way too slow.

A couple extra tips for coolantless manual machines and carbide:
-From working on manual lathes and mills with carbide, 2500 RPM, and no coolant my arms have quite a few spots where chips landed and made nasty little burns. The scars take a long time to fade too.
-When using face mills you will want to feed fast so the chips all head in one direction and you can stand away from them. If you get inclusions or chip dragging scratches, a spraybottle with coolant will improve your finish face milling as well.

This is all in my fairly limited experience. I am sure some of the old tymers can give better tips for improvement and how to stay safe. If I know I am going to really be cranking on a face mill I either put up some kind of air to blow the chips away or mill in just one direction so I know where the chips will go. I also wear a face shield because usually the chips will be brown.