Common endmill shanks & roughing endmills

[chris.trotter]

This is probably a highly relative question, but here goes...

For aluminum and mild steel hogging work, and to save endmill life, I'm looking to get a roughing endmill (thinking 3/4" shank size), like this: KBC M-42 8% Cobalt Roughing / Hog Mills - Coarse Tooth

My reasoning for picking that size is:
- my mill type (SX2P/LMS 3960) can deal with 1/2" endmills at most (in steel, very light cuts, without blowing up w. chatter - I only know this from forum posts, not experience)
- a roughing endmill allows you to cut more with less (at the cost of surface finish)
- therefore 3/4" should be the max effectiveness for roughing endmills (?)

That means I need an R8 endmill adapter/arbor thingy. (I have an ER16 collet set, don't want to jump into an ER32 set quite yet)

Questions:
- is 3/4" shank "uncommon"? (will another size provide a wider scope)
- is 3/4" roughing too enthusiastic a size for my size mill?
- should I be pointed in another direction?

 

[Groundhog]

I think the end mill type is just right - cobalt is not as brittle as carbide and does not need the faster speeds of carbide. I run HSS and cobalt end mills on my small CNC mill almost exclusively.
However, I think that 3/4" is probably a little large. If I were you I would stick with 1/2" (or whatever is the largest ER16 collet you have). I only use roughing end mills up as large as I can mill with a finishing end mill. I just run them faster (usually about the same RPM, but faster travel - depending on the mfgr's recommendations).
As you get more experience you can try larger if you want, but if you start with something already wrong (too much end mill for the HP or rigidity) it can be very hard to figure out what is wrong - because nothing you can do will fix it.

 

[chris.trotter]

Unfortunately I only have up to 10mm ER16 (which is just tiny), so I need to get another holder regardless of 1/2 or 3/4. Will do some more looking to see what others have encountered. I'm fine with dropping the $100 on a holder/endmill, but would like to only do that once.

Thinking more, 1/2 would probably be wisest for compatibility with different endmill types - 1/2 finishing IS probably the maximum, 3/4 finishing would def not work.

Well there we go then - thanks!

 

[mattthemuppet2]

with that size mill just stick with 3/8 shank tools. You can remove plenty of metal quickly with a 3/8 rougher. Get a 3 flute for alu and a 4 flute for steel. Cobalt won't hurt, but standard HSS will be just fine.

 

[Ken from ontario]

Chris, when I first got my mill (CX612, similar to LM S3960)just over a year ago, I asked a lot of questions here about sizes/types of end mills etc. the best advice I got was to stick with smaller diameter end mills , I now have a few 1/4" , 3/8" and 1/2" in both stub and regular lengths. 3 flute(center cutting) end mills worked the best (4 fl,is also fine) ,the better the quality of the end mills , the longer they seem to last(Niagara, WIDIA,YG-1,OSG USA).
HSS and cobalt are what I always search for, here are a few examples:
https://www.amazon.ca/gp/product/B0080D80M4/ref=oh_aui_detailpage_o02_s00?ie=UTF8&th=1
https://www.amazon.com/dp/B003CYKLKA/_encoding=UTF8?coliid=I2L5RHKOVWIHST&colid=T6FVA71OODYI&psc=1
https://www.amazon.ca/gp/product/B0080CV8ZG/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

 

[chris.trotter]

I now have a few 1/4" , 3/8" and 1/2" in both stub and regular lengths.

Ken, do you have any roughing endmills? Experience with them on that mill?

The operation I have in mind with this line of questioning is purely roughing/hogging material off. Ideally I can re-use the endmill holder for other operations (ball-end, finishing, dovetail), but not world-ending if I have to buy another. They are only $35, so if I have to buy another later on, so be it. At that point I'd probably just move to an ER32 collet system anyways.

For finishing operations I definitely plan to only use smaller endmills for exactly the same reasons you got, but for roughing, should be less of a concern.

 

[Groundhog]

I agree with M - 3/8 is my go-to end mill size whether in roughing or finish. I probably have 2-3 times more 3/8 than any other size (and I have quite a few)!

 

[woodchucker]

I use both 3/8 and 1/2 shank roughing endmills. I don't use larger. Both fit in my endmill holders. I have a few 3/4 " shank s, and 5/8 but no way to hold them now. And don't think I'll be upsizing my holders soon.

 

[chris.trotter]

I agree with M - 3/8 is my go-to end mill size whether in roughing or finish. I probably have 2-3 times more 3/8 than any other size (and I have quite a few)!

And are you running a mill about this size?

I use both 3/8 and 1/2 shank roughing endmills. I don't have larger. Both fit in my endmill holders. I have a few 3/4 " shank s, and 5/8 but no way to hold them now. And don't think I'll be upsizing my holders soon.

Thanks woodchucker, but your mill is comparatively enormous.

The 3/8 seems to be the averaged choice here, will go with that.

 

[Ken from ontario]

Ken, do you have any roughing endmills? Experience with them on that mill?

The operation I have in mind with this line of questioning is purely roughing/hogging material off. Ideally I can re-use the endmill holder for other operations (ball-end, finishing, dovetail), but not world-ending if I have to buy another. They are only $35, so if I have to buy another later on, so be it. At that point I'd probably just move to an ER32 collet system anyways.
.

As I mentioned I asked /learned a lot from the more experienced members here and saved a bundle by not buying the types/sizes of end mills that were just wrong for my small mill,you and many others with small milling machines (including myself), we always need to be aware of the the depth of cut, speed/feed, and the lack of rigidity of these machines.
For me 1/4" (3/8" shank) roughing end mill, preferably stub length ( or even regular cutting length for deeper DOC. ) has been the most used end mill for hogging material off,but also 3/8"x3/8" x2.5" or 5/16" (all roughing ) end mills has worked just as well, I try to read the description of the end mill care fully nowadays for example, some end mills are recommended for cutting Aluminum so if I'm cutting mild steel I often use the ones that are for MS applications .