Choosing Length of Cut for Endmills?

[markba633csi]

Bruce your dad was pretty generous- I think even two diameters is pushin' it
Depends on the size of the chuck tho and the stock

 

[Michael303]

Thanks, everyone, for the replies. This feedback has clarified things for me quite a bit.

So, practically speaking, I would buy end mills in 1/4" increments. Buy centercutting when possible, sharp corner radius unless a radius is called out and have 2 or 3 flute end mills for pockets and slots and 4-6 flute end mills for profiling. Buy high helix 3 flute end mills for aluminum if you can afford them and please, please buy roughing end mills. Get coarse pitch roughers for slotting and fine pitch for profiling - they run 20% faster on both feeds and speeds and will help your finishing end mills last much longer. Buy HSS or cobalt for most jobs and get carbide for deeper cuts or when you have to hold really tight tolerances.

Why are 2-3 flutes preferred for slots and does it apply to steel and aluminum? I hadn't thought about roughing endmills. Thanks. What advantages can HSS and cobalt have over carbide?

If I could have just one endmill it would be a HSS 3/8", 2-flute, double ended endmill made in USA with about 1" flutes
Of all the ones I have I reach for that one the most
-M

Thanks for the insight. Do you have any go to brands for HSS?

 

[markba633csi]

Cutting clean slots is difficult because the chips tend to bind up in the slot and give a rough, choppy finish. So fewer flutes works better, gives the chips someplace to go
Good question about USA endmills. I think Cleveland and Niagara are still making them here. Brubaker, Morse, SGS are some others. I'd do a search
Most of mine are old brands that are out of business now like Putnam and Do-all, I purchased an estate sale lot with new and nearly new ones but they are quite old. They don't have a "use by" date tho

 

[Michael303]

Cutting clean slots is difficult because the chips tend to bind up in the slot and give a rough, choppy finish. So fewer flutes works better, gives the chips someplace to go
Good question about USA endmills. I think Cleveland and Niagara are still making them here. Brubaker, Morse, SGS are some others. I'd do a search
Most of mine are old brands that are out of business now like Putnam and Do-all, I purchased an estate sale lot with new and nearly new ones but they are quite old. They don't have a "use by" date tho

That makes sense. I would have guessed more flutes would clear the chips better. Thanks for the info.

 

[mikey]

Why are 2-3 flutes preferred for slots and does it apply to steel and aluminum? I hadn't thought about roughing endmills. Thanks. What advantages can HSS and cobalt have over carbide?

As Mark said, fewer teeth for better chip clearance primarily but you are also able to feed faster given that feed rates are rated by inch per tooth. Edit: I meant that 2 flutes clear faster but 3 flutes can be fed faster while still clearing well.

HSS and HSS-cobalt end mills are cheaper, very sharp, less brittle and work for most materials. Carbide is much stiffer than HSS so it deflects less ,which helps accuracy. It can also go deeper so for deep cuts or where there is a lot of edge contact, carbide end mills work better. You can also run them at higher speeds and feeds so they are more efficient. However, they are more expensive and brittle - push too hard and you'll hear a "tink" and the end mill is gone. Hobby guys tend to think that throwing money at a process is the way to go but HSS-cobalt end mills are far and away the most useful in the hobby shop.

 

[Janderso]

In my experience, an aluminum 2 flute extended end mill did a beautiful job milling out 80%ers. (deep channel)
I'd blow the Kool mist to help evacuate the mountain of chips.
I would finish with a 3 flute finishing end mill high speed.