How much can I take out?

[ericc]

Weak mill and wrong inserts. A bandsaw, even a small one, is more appropriate.

 

[homebrewed]

For my own education, I've got a question about the use of a roughing end mill in this situation. The end of the mill doesn't appear to be shaped any differently than a standard end mill. So I wouldn't expect it to be any faster than a standard mill (with the same number of flutes) if doing facing work. Am I wrong? If so, why?

Thanks

-Mark

 

[Pcmaker]

I think roughing end mills are meant to attack from the side

 

[JimDawson]

End mills in general are designed to cut both on the end and side. Roughers due to their design reduce the power requirement and machine/chip loading. The chips come off of them as small chunks rather than a long spiral chip as with a normal end mill. You can many times use a rougher to make a full depth cut, but you may have to slow down the feed rate a bit depending on the material and your machine.

Many times when I wear out the first 1/4 inch or so of the end of any end mill, I'll use the upper part of the end mill for side cutting.

 

[Pcmaker]

Broke my 1/2" HSS 4 flute regular end mill trying to use it as a roughing end mill. The mill kept on "jumping," too.

 

[P. Waller]

The grooves on the cutting edges are chip breakers, as mentioned they produce very small manageable chips but will not provide a hobby shop friendly finish. This greatly reduces the cutting power needed.

They will bang out some heavy roughing however so are invaluable.

They are often available in coarse and fine grinds, choose what works best for the job at hand.

 

[JimDawson]

Broke my 1/2" HSS 4 flute regular end mill trying to use it as a roughing end mill. The mill kept on "jumping," too.

Might be time to head to Harbor Freight and pick up their end mill set. https://www.harborfreight.com/20-piece-titanium-nitrade-coated-end-mill-set-5947.html I use them around here for utility work, and they're cheap so when you break one or burn it up you're not out much. It really sucks when you take a new $35 end mill out of the package and instantly break it. I have quite a collection of really expensive end mill shanks.

''Jumping'' might indicate that you were making a climb cut rather than conventional cut, is this possible? Did you lock the axis that you were not using? On your machine with a 1/2 inch standard end mill, I might start out at about 0.200 DOC and not more than 30% cut width (about 0.150), and around 600 RPM. Your machine is capable of doing very nice work, but it's just not heavy enough to really hog off material.

 

[Mitch Alsup]

Broke my 1/2" HSS 4 flute regular end mill trying to use it as a roughing end mill. The mill kept on "jumping," too.

Too much DoC (depth of Cut) and probably too high a feed rate.

 

[tcarrington]

Having a PM25 also, I will attest that in most situations you won't be able to climb cut to remove a lot of material. (I usually limit climb cutting to aluminum and then with 0.010 max DOC and less than standard feed. Climb cutting on my machine is used for finish, the last cut and mostly either a spring cut or 0.002.

With conventional milling, correct RPM and feed, you can be limited by the spindle horsepower. All the advise given above should lead you to a good solution. I tend to use 4 flute more often than the folks on larger and stiffer machines. As long as the chips clear, keeping more flute contact helps, IMHO. The mild steel I have cut stays lubricated with regular cutting oil (I like the way it smells, too). I use the smoke as an indicator in regard to how fast to hand feed. Slow, no smoke and you can speed up the feed. Go too fast and you drive all the lubricant off. If you hear your spindle slowing down, slow the feed. That might help with such a mill as you have.

The only thing I will add is check your jibs and make sure they are as tight as can be allowed. Lock the axis you are NOT feeding. Our machines are light and will not just stay in place.

 

[Downunder Bob]

Broke my 1/2" HSS 4 flute regular end mill trying to use it as a roughing end mill. The mill kept on "jumping," too.

If the mill kept jumping, were you by chance climb milling? NEVER climb mill when roughing, only ever for a light finishing cut, especially with lightweight hobby machines