Choosing Length of Cut for Endmills?

[Michael303]

I'm looking to buy some endmills in 1/16" increments from 1/8" to 1/2" for an upcoming machine shop class and just for general use, not a specific job.

Is there a consensus or theory on whether it's better to spend a little more to get end mills with a longer length of cut or would it be beneficial to buy more stubby length tooling because (I'm assuming?) it's probably a little less likely to break?

Any feedback is appreciated.

 

[benmychree]

You got it nailed! The longer they are, the easier to break. Use the shortest tooling that will do the job.

 

[mikey]

Best practice is to use the shortest flute length possible to reduce deflection. This improves accuracy and finishes. However, given that each work piece is different, it will be insanely expensive to have an end mill that just fits the bill every time. 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.

 

[RJSakowski]

Longer end mills also flex more and are more prone to chatter. You can only choke up so much before the you hit the flutes.
sometimes you need a longer reach and it's nice to have it available but longer end mills wouldn't be my first choice in building an inventory.

 

[markba633csi]

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
Oh and I forgot to say centercutting

 

[Winegrower]

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

That’s an interesting thought. For me, it’s a 1/2” 4 flute carbide from YG1. There was some special awhile ago, and I got a half dozen for around $10 each. These guys are terrific. Yes, I keep them in their tubes.

 

[markba633csi]

Carbides are nice too, I have a few
I have an embarassingly small endmill collection, but I make the most of it
I did snap a 3/16" chinese one yesterday, no big loss (2$) they are brittle as glass

 

[rabler]

That’s an interesting thought. For me, it’s a 1/2” 4 flute carbide from YG1. There was some special awhile ago, and I got a half dozen for around $10 each. These guys are terrific. Yes, I keep them in their tubes.

1/2" 4 flute carbide would be my goto endmill if I don't have a specific size need. It tends to be a good price point, big enough to be sturdy. I don't keep 'em in their tubes, I have a board with blind holes drilled to keep them out where I can see them easily, same board that keeps the drill chuck, collets, and toolholders for the mill. Tubes for the infrequently used or where I have multiples.

 

[BGHansen]

My go to in my Tormach 1100 is a 1/4" 4-flute carbide. Go with 4-flute 3/8" or 1/2" on the Bridgeport. Not adding anything but the shorter the stick-out, the more rigid the set up.

I think of it much like turning on a lathe. My dad was a shop teacher and told kids to not run stock more than 3 diameters outside of the chuck unless they were turning between centers. I violate it all of the time, but manage it by depth of cut and feed rates. Imagine sticking a 1/2" steel round out of a lathe chuck 10" and trying to take 0.040" off a side. You'd be taking a trip to "Chatter City, USA" or "Buckle Town, USA". Same principles hold true for tool stick out. You can get away with a deep end mill but need to be careful with the feed rates, width of cut and depth.

Bruce

 

[Aukai]

I have been adding to my inventory by looking on ebay for endmills new. I will not buy pre owned now, but if you keep looking at the new, and keep the brand names in mind, very good deals pop up.