Correct way to hold end mill?

[homebrewed]

I put 3 iGaging remote-reading DROs on my mini mill. The remote readout feature is nice because it gives you more options on how to install the scale and sensor on your mill. These can be found on a number of online retailers. You don't get all the nice features a true DRO system offers, but if you really want all the bells & whistles you can interface the things to a tablet via the TouchDRO system or similar. Google Yuriy's Toys for more info on his system. I haven't gone that far but many sing its praises.

 

[shooter123456]

I think the right answer is an endmill holder, but good collets work too. I use an ER32 collet chuck for my endmills.

The concern is having too much run out with a drill chuck / cheap collets which will damage your endmills.


I don't know your machine, but it looks like one of the common Sieg built mini mills sold by many vendors. You might look at Little Machine Shop for the DRO, they offer packages for many of these small mills.

https://littlemachineshop.com/products/product_category.php?category=-1536942993

The concern with holding an end mill in a drill chuck is actually one of safety, unrelated to run out. The drill chuck is held onto the arbor by a jacobs taper, which means there is no positive retention to prevent pull out (Like a drawbar holding a collet). It is designed to handle forces straight up into the spindle when drilling. When milling, there will be sideways force and downward pulling force. If the drill chuck is pulled out of the taper, it is now a spinning projectile with a sharp tool in it which is obviously dangerous for the user, as well as potentially damaging the workpiece, the machine, or other things nearby.

Collets are the way to go. I can't tell if you have the R8 or MT3 spindle, but the matching collet will hold the tool just fine. I had no issues with R8 collets on my mini mill, even when I had it CNCd and running a 1.5 HP treadmill motor. Just keep an eye on runout for the smaller tools as too much can cause them to break.

 

[Aaron_W]

The concern with holding an end mill in a drill chuck is actually one of safety, unrelated to run out. The drill chuck is held onto the arbor by a jacobs taper, which means there is no positive retention to prevent pull out (Like a drawbar holding a collet).

I think you are talking about using an endmill in a drill press. The drill chuck for my mill is threaded onto an MT arbor and held in place with a draw bar. I think an arbor and draw bar is a common method for holding drill chucks in a mill.

 

[shooter123456]

I think you are talking about using an endmill in a drill press. The drill chuck for my mill is threaded onto an MT arbor and held in place with a draw bar. I think an arbor and draw bar is a common method for holding drill chucks in a mill.

Ahh, I see. No, I was specifically referring to using the drill chuck in a milling machine with an end mill. The one that came with my mill, and all the drill chucks I have ever bought, are just chucks with a jacobs taper, pressed on an arbor like this one: https://www.mscdirect.com/product/details/92302413

Up until now, I did not know they made threaded drill chucks.

 

[GrayTech]

For Shure with that type of mount you can use your drill chuck to hold tools if runout is good enough, but a arbor with an ER32 collet chuck will reduce tool and chuck stick-out/flex, and increase your z axis capability.

Metric ER collects didn't work well for me on most inch size tools, especially a problem with fly cutters and face mills etc. I think they just lack good contact, my inch collects are a press fit on inch tools with low runout and work very well. I think the inch collects are the way to go for inch tool. You can find them on eBay for around $60 for arbour and collet set together.

Sent from my H3123 using Tapatalk

 

[P. Waller]

Yes the proper way to hold an end mill is with a collet.

The "proper" way to hold an endmill is the way that the machine spindle allows, many machines will not hold a collet in the spindle directly. Therefore a collet tool holder, setscrew tool holder or shrink fit holder is required.

The advantage of holding a tool in a tool holder in a collet spindle machine it that the Z axis zero remains relatively constant if the tool is removed and returned to the spindle. A collet spindle will not repeat nearly as well in Z as a Cat, BT or MTB spindle. If you do not do many tool changes then by all means hold them in a collet.

 

[wa5cab]

In fact, with ER collets, I've read it's actually a little nicer to get metric as they are usually 1mm range with 1mm spacing, no gaps.

With Inch marked ER collets, it depends upon which set you buy. Most manufacturers seem to make their sets two ways. And then some of them offer sets in 1/16" increments (fewer collets) which don't or won't cover the contiguous range from the smallest nominal diameter to the largest.

The inch size marked sets are easier to use if you are using inch size milling cutter shanks because they are direct reading. If you want to use a 1/8" shank cutter, you use the collet marked 1/8".

 

[38super]

Fully engage the end mill shank in the collet, ensure collet nut is tight. Have had end mills try to walk out when I needed stick out.

 

[ttabbal]

Look up the torque spec for whatever collets you use. They want to be surprisingly tight. ER40 is around 100ft/lbs. The only time I've had something slip was when I didn't tighten it properly.

 

[wa5cab]

I'll add that it also depends upon how much trouble it is to remove the drill chuck and install the collet or collet holder. I can't tell from the photos how the drill chuck is attached to the spindle. But in general, milling cutter shanks are harder than drill bit straight shanks. The drill chuck jaws are normally hardened, so make a poor way to hold a hardened cutter shank. Unless you very seldom need to hold a hardened cutter, you should use some sort of collet, all of which have the advantage over the drill chuck of having much more surface area in contact with the cutter shank.