Best End Mill for Side Milling Steel

EmilioG

EmilioG

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I’m milling O1 tool steel and some bronze and 4140 1/4” thk and would like to know what the best type of end mill to use in order to get a nice square finish. I can’t mill two ends because they’re already at dimension.

Carbide seems to work best with annealed O1 tool steel. Should I use 4 flutes? Minimum stick out of course.
One attempt came out with heavy scallop marks. Climb mill? Which side of the vise should I use?
 
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4 flutes should be fine.
"heavy scallop marks" rigidity? what is your mill?
 
Mill: Older BP J head. Definitely needs a new vise. 1/2" carbide end mill, 6 flutes. Maybe lighter cuts would help plus 4 flutes.
An end mill can sometimes start to flex and vibrate like a tuning fork or the part may need more support. Maybe a 1 2 3 block?
 
your problem is too much DOC for the rigidity of your machine...

I would disagree on carbide for this application. A really SHARP new HSS cutter running climb mill on a skin cut at a low RPM is likely to give a better finish..
 
I'll try lighter cuts. My carbide end mills have been working very well for steel and aluminum.
The 1/2" carbide is run at 5200 RPM's and usually leaves a nice finish. Guhring end mills. HSS tends to dull quickly on tool steel.
I may switch my project to 4140 for the other small parts. O1 is really tough. Most of my HSS cutters are cobalt, so I may try those.
 
When I side mill and want good finish I finish up with a 2 -3 thou depth of cut, crank up the speed a bit and feed quick enough than I get nice needle chips not dust. If I want good finish side milling I make sure I am using fresh or near fresh endmill, not one of my beaters
 
I think workholding also plays a role. If I clamp the work with enough metal in the middle of the vise plus use low parallels, with minimal stick out.,
I should get better results. Basic stuff. Thanks to all.
 
I usually use 4-flute end mills for profiling cuts and try to use the part up near the shank to do it if I can; it's stiffer up close to the collet. 4-flutes work well in profiling cuts like this because chip clearance is less of an issue and they finish better than 2 or 3-flute cutters.

I normally will conventional cut O-1 and leave 0.001-0.002" to climb cut in a finish pass. This leaves a very nice finish. Which direction to cut? If the cut is on the end and it is sticking out of the right side of the vise, take the cut on the left side of the end mill and feed away from you; this is a conventional cut. A climb cut is also on the left side but the feed is toward you. Does that clarify or confuse things?

Edit: in a conventional cut, the table will move toward you when the end mill contacts your work piece as above. In a climb cut the table moves away from you.

You can use HSS, cobalt or carbide to cut O-1; all work well but I usually reserve my carbide end mills for deeper cuts or where there is a lot of side contact. Carbide is stiffer and doesn't deflect as much but they're more expensive so I tend not to use them unless I need the stiffness.
 
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Makes sense. Very clear. I like that you use the top end of the EM near the shank. Haven't thought of that.
I suppose that if the part thickness is .250", that it would be better to use something like a 3/8" 4 flute end mill.
The larger EM has the flutes spaced wider apart. Better chip clearance? I have bright uncoated HSS and TiAin, TicN and Tialn coated EM's that I can use. Niagara Cutters and Guhring being two of my top 3 favorites. This is all good information that will live on as a great resource to other HM's.
It's very basic, but even simple operations can become frustrating to someone starting out or is new, like me. The Devil is in the details. :)
 
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