View Full Version : Best size endmill
08-17-2001, 11:57 PM
If any of your slots are open at one end, drill and bandsaw might rough them out.
09-30-2004, 09:31 AM
I've got a bunch of slotting to do in roughing out some brackets in 3/16" hot-rolled angle and am wondering what the best size endmill is for just rough cutting in general? 1/4" mills don't have to remove much mtrl but you get a lot of deflection and are easier to break. 1/2" mill goes fast but is removing a lot of matl. Is 3/8" the best compromise? I haven't bought that size cause I don't like figuring odd size numbers on the DRO. How come endmills don't come in decimal sizes like .200, .300, .400 that are easy to figure tool offsets from? What's a good combination of tool, speed, and feed for this sort of thing on my old bridgy running flood coolant?
09-30-2004, 10:26 AM
The best size is the one best suited to the application. It sounds like you want to decide what size to make your slots. If that's the case, then you have to decide based on what the function of the part is, etc.
If you are using HSS tooling, and you can afford a carbide endmill, then you can get each slot done faster without increasing your slot size.
I apologize if I seem to be doing a Captain Obvious imitation--I'm just trying to cover the basics.
09-30-2004, 10:59 AM
I don't care what size the slot is as I'm just cutting out an irregular shape and is faster to do with slots than a bunch of peripheral cuts. I just seems to me that there must be a obtimum size to use for fast, reliable slot cutting. Not counting tool grade (HSS, carbide, etc) or type (roughing), what do you guys who have been doing this a long time use when needing to whack off excess material?
09-30-2004, 11:34 AM
If finish is not a big concern, try using a roughing end-mill, the fine pitch ones don't give that bad of a finish, and you get a better chip.
09-30-2004, 11:41 AM
I would use a roughing tool the size of the slot you require. Just crank down the gibs well and use a squirt bottle with coolant. Also perhaps going through the material in two cuts (Depth Wise ) might help the occasional tool wandering that I have encountered when Im milling slots. Remember its just a slot and washers were invented to cover up our hacks. Madman
09-30-2004, 12:09 PM
On the matter of size: I'm not a real machinist, but my son-in-law is, and he advised me that 1/2" is a good, optimum choice for just removing material, when no other factors dictate something else. I too like the roughing endmills.
09-30-2004, 01:07 PM
Sounds to me like you are just cutting out a shape, not needing a slot. Short of having a plasma cutter table, well- I would think that a 3/8 endmill might be a tad large, and maybe a 1/4 in would be about right, except for the tendency for it to break. Maybe there's a stronger version of the endmill that you could use. Do the cutting with the upper part of the cutter, as close to the body as possible, to minimize the chance of breakage. High speeds, coolant, etc. Just some thoughts.
09-30-2004, 01:10 PM
As to which size will remove the most material in the least time, I would suspect it will depend on a lot of factors. The size and HP of your mill, the material being machined, the speeds and feeds, etc.
I haven't been at this long enough to make any general suggestions. There are text books that will talk about the various factors but if you have a specific production situation that you are trying to optomize, you may have to experiment with the various factors to find the best combination.
In short, I don't think there is a single definitive answer.
As for decimal size mills, they do exist but the fractional sizes and even the metric sizes are a lot more common.
Besides, .375 is a decimal size. ;< ))
10-01-2004, 06:59 AM
3/16" thick ain't much,a good quality two flute will run smooth at 675rpm dry or 1125 with coolant assuming you can plunge it on through the material.
It will help if you have an air jet blowing the chips out of the cut.