View Full Version : 1" Shank endmill in R8 spindle ??

12-29-2012, 11:57 AM
Anyone done / doing it ?
My son works in a big CNC shop, brought me home a bucket of mostly used up end mills.
Searching through the bucket, some of these still look useable, for roughing anyway. Trouble is, they're mostly 1" shank, some Weldon, some threaded shanks.
Some nice 1" roughers, E/mills up to 1.750.
What's the best way to use these in an R8 spindle ??

12-29-2012, 12:04 PM
I have R8 collets up to 1 inch (maybe ittle more) , but I typically use EM holders with set screws for the large sizes.

12-29-2012, 12:09 PM
Use a 1" R8 end mill holder.
You can get R8 collets that size, but the walls
are awfully thin.

12-29-2012, 12:14 PM
Like has been said here, use a solid holder. 1" R8 collets are fairly flimsy.


uncle pete
12-29-2012, 12:45 PM
An ER-40 collet would do it, but if you had those then you wouldn't have posted the question. So the endmill holder would be the most cost effective.


12-29-2012, 12:54 PM
A 1" R8 collet is pretty much useless for anything. A 7/8" collet is usable but fragile. I've seen 2 or 3 with one segment broken off. For R8, 3/4 is the biggest collet you can go reliably.
I commonly use the setscrew style endmill holders of 1, 1-1/4, and 1-1/2 with good results, but you have to use some common sense along with them and not push the cut too much.

12-29-2012, 01:37 PM
Yep, my R8 collet set goes to 7/8" and that one is pretty thin, can't imagine a 1".
Guess I'm shopping for a 1" E/M holder. I was aware of E/M holders, just thought there might be another / better way (and don't have one yet).
Thanks guys.

12-29-2012, 01:42 PM
I was aware of E/M holders, just thought there might be another / better way (and don't have one yet).

they are the better way. :)

loose nut
12-29-2012, 03:27 PM
I have a 1" r8 collet that gets around the thinness problem by having the end stick out farther and is thicker. Solves one problem but is less ridge because of the overhang. Still works for light cuts.

12-29-2012, 06:03 PM
For plastics and wood, probably yes.

Metals, not so much. :p

Even aluminum would be questionable with anything but the shortest length of cut.


12-29-2012, 06:24 PM
We have a 1" and 1.25" R8 end mill holders. The R8 holder goes in normally and the endmills are held with 2 set screws.
There is a large barrel hanging out of the bottom of the R8 shape.
Jeff at Tools4Cheap has a set of them.
I am not affiliated with Jeff or his business, just identifying the product.

12-29-2012, 06:52 PM
I've also got the 1" and 1-1/4" Weldon shank style R-8 holders. You can see them in the lower left side of this drawer. As stated by mc_n_g, they do extend from the gauge line of the spindle quite a bit, but at leas tthey've got a significant grip on the end mills.


12-30-2012, 12:06 AM
I'd suggest that the large (1" up) roughing end mills are pretty much a waste for an R-8 sized mill. You simply won't have enough rigidity and power to run it properly through steel. With aluminum a properly sized end mill will last so long you won't really have that much need for free large roughers. The free end mills can end up with lousy finishes, no savings in time, and greater wear on your mill. The exception to all this might be for something like a 1" counterbore, with the center already cut out.

If you have sharp larger finish cutting endmills, particularly with 4 or more flutes, they should be fine for cutting aluminum and perhaps treated as a sort of fly cutter in mild steel -- cuts and feeds that avoid significant vibration.

12-30-2012, 03:41 AM
I'm not sure using large endmills in a machine with an R8 spindle is a good idea. That will be hard work for
a light machine like a turret knee mill.

12-30-2012, 05:18 AM
I routinely use 1" end mills on our Series 1 & Series II Bridgeports at work. I like the stability that a larger end mill offers when facing large cross-sectional workpieces and also for extrusions such as larger pieces of angle or C channel. Long end mills of smaller diameters necessary for such applications are prone to break when a snag occurs on extrusions. The 1" mills are beefy enough to take deeper cuts without risk of breaking. We have the type of adaptors shown in the lower left of PixMans photo above. They work fine.

12-30-2012, 07:58 AM
Of course there's little chance of fully engaging a 1" or larger cutter on a 1HP Bridgeport, and I'm fully aware of that.

I also use them primarily for tasks that DATo mentioned. I often have a tall workpiece in the vise and want to get the top surface and an end (or two ends if longer than the vise) square. With a large diameter tool I can take a light cut across the top then drop it down and get perfectly square ends. A 1" diameter end mill with 2-1/4" of cutting length is far more rigid than a 1/2" diameter end mill with the same cutting length.