School me on ER collets...

[1HobbyMachinist]

I'm new to ER collets, I'm well versed in R8 collets. I just bought a couple ER40 collet holders from Glacern for a good price, and a set of collets from Shars.

So, how do they compare to r8 collets in real life? Do they grip harder or is tool slippage a problem? Realistically, on a rf45 machine, will I even notice the loss in rigidity? What can I do with them? What can't I do with them? Please share all your ER collet wisdom with me

Mike

[txcncman]

They are almost totally different animals. I have never noticed rigidity difference, except maybe the effective length of the tool tip to the spindle will be more. You can do more because you have a larger size range to work with now. Hopefully you have the horsepower to match.

[awerby]

They work a bit differently from R8 collets. You have to slip the collet into the closer nut until it snaps into place. Then you can insert the tool and tighten it, using 2 wrenches. If you neglect the snap-into-place step, then it will never seat correctly. But at least there's no drawbar that you have to break loose...

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[1HobbyMachinist]

They work a bit differently from R8 collets. You have to slip the collet into the closer nut until it snaps into place. Then you can insert the tool and tighten it, using 2 wrenches. If you neglect the snap-into-place step, then it will never seat correctly. But at least there's no drawbar that you have to break loose...

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

So THAT'S why the nut is machined with that weird off center groove in it...
I already made a few cuts without doing that, but I will do it correctly from now on. Thanks a lot for the tip!

[BobWarfield]

ER collets are great--they perform better than either R8 or set screw end mill holders. Some complain they're experiencing collet pullout. ER's take a lot more torque than you might imagine. Here are a couple of articles to help along those lines:

Getting the Best Performance from ER Collet Chucks « « CNCCookbook CNC Blog CNCCookbook CNC Blog

Toolholding in Collets: How to Avoid Tool Pullout « « CNCCookbook CNC Blog CNCCookbook CNC Blog

I say they perform better for a variety of reasons. Consider this article, for example, which compares ER collets against much more expensive tool holders:

What Are the Best Toolholders? « « CNCCookbook CNC Blog CNCCookbook CNC Blog

Here's a tip--look for ball bearing caps for the collet chucks. I've bought some from Arc Eurotrade on the cheap. They make it easier to torque down the collet and increase their gripping power quite a lot.

TechniksUSA says it increases the grip 75%:

ER Bearing Nut

I use ER collets exclusively for cutters 1/2" or less.

Best,

BW

[1HobbyMachinist]

ER collets are great--they perform better than either R8 or set screw end mill holders. Some complain they're experiencing collet pullout. ER's take a lot more torque than you might imagine. Here are a couple of articles to help along those lines:

Getting the Best Performance from ER Collet Chucks « « CNCCookbook CNC Blog CNCCookbook CNC Blog

Toolholding in Collets: How to Avoid Tool Pullout « « CNCCookbook CNC Blog CNCCookbook CNC Blog

I say they perform better for a variety of reasons. Consider this article, for example, which compares ER collets against much more expensive tool holders:

What Are the Best Toolholders? « « CNCCookbook CNC Blog CNCCookbook CNC Blog

Here's a tip--look for ball bearing caps for the collet chucks. I've bought some from Arc Eurotrade on the cheap. They make it easier to torque down the collet and increase their gripping power quite a lot.

TechniksUSA says it increases the grip 75%:

ER Bearing Nut

I use ER collets exclusively for cutters 1/2" or less.

Best,

BW

Thanks for the info Bob. I'll look into one of those bearing nuts. I really need to be able to hold a 1/2 end mill securely for a project I'm working on, and so far my luck with r8 hasn't been that great. It's good to know I can put a good bit of torque on the er40 chuck. Now I'm off to youtube to see if I can find some vids of the bench setup people use to tighten them...

[SCzEngrgGroup]

"so far my luck with r8 hasn't been that great." - You're doing something very wrong.... An R8 collet can hold a 1/2" endmill quite securely through cuts far tougher than an RF45 can handle. How are you torquing the drawbar? For R8, you need on the order of 25 foot-pounds torque on the drawbar. You want the tool shank, and the inside of the collet to be VERY clean, and bone dry. You want a light coat of oil or light grease on the taper on the outside of the collet. If that doesn't give you secure holding, then there is something wrong with the taper in your spindle, or you have a set of cr@ppy collets. Keep in mind too that each R8 collet works for only ONE specific size of shank. You cannot put a 12mm tool in a 1/2" R8 collet, and expect it to hold.

Regards,
Ray L.

[BobWarfield]

The bench setup part is a bit disappointing as most of the world don't use R8 or straight shank TTS-style holders for CNC. It's easy to get a CAT40 tightening fixture, but R8 is harder.

For the time being, I prefer collet chucks that have wrench flats. I can lock them up in a vise with soft jaws and put some serious torque on one.

Down the road, I was recently over at a friend's shop who has a Romi CNC toolroom lathe. We took some 4140 round and put an R8 taper in it (so easy to do with a CNC lathe). It will eventually become both a tightening fixture and a tool setting fixture as the top and bottom are ground parallel so it can sit on a surface plate while I use a height gage to measure tool height.

Cheers,

BW

[1HobbyMachinist]

"so far my luck with r8 hasn't been that great." - You're doing something very wrong.... An R8 collet can hold a 1/2" endmill quite securely through cuts far tougher than an RF45 can handle. How are you torquing the drawbar? For R8, you need on the order of 25 foot-pounds torque on the drawbar. You want the tool shank, and the inside of the collet to be VERY clean, and bone dry. You want a light coat of oil or light grease on the taper on the outside of the collet. If that doesn't give you secure holding, then there is something wrong with the taper in your spindle, or you have a set of cr@ppy collets. Keep in mind too that each R8 collet works for only ONE specific size of shank. You cannot put a 12mm tool in a 1/2" R8 collet, and expect it to hold.

Regards,
Ray L.

Yeah I tried cleaning the collet and tool and applying lube only at the threads, outside surface and under the drawbar nut. Turns out it was just a ruined r8 collet - my fault. I was turning some 1/2" stock a while back and I got too close and nicked the bottom of the collet. I guess I raised a burr in there or something. I was pretty dissapointed, my endmill kept pulling down in what I consider to be pretty light cuts in 4140
I have since ordered a set of Crawford collets, but I haven't had a chance to test them.

I think my primary problem is my method for tightening; drop the mill in the lowest gear, and tighten the drawbar with a quick motion until it spins. I usually do this a couple times. What I really need is a spindle lock or a wrench that can grab the splines of the spindle. I'm not opposed to using a torque wrench to tighten, but right now it would be useless without one of the spindle locking tools.

[1HobbyMachinist]

The bench setup part is a bit disappointing as most of the world don't use R8 or straight shank TTS-style holders for CNC. It's easy to get a CAT40 tightening fixture, but R8 is harder.

For the time being, I prefer collet chucks that have wrench flats. I can lock them up in a vise with soft jaws and put some serious torque on one.

Down the road, I was recently over at a friend's shop who has a Romi CNC toolroom lathe. We took some 4140 round and put an R8 taper in it (so easy to do with a CNC lathe). It will eventually become both a tightening fixture and a tool setting fixture as the top and bottom are ground parallel so it can sit on a surface plate while I use a height gage to measure tool height.

Cheers,

BW

Well, no wonder I can't find one... I guess I'm going to have to buy a couple wrenches for my collet chucks. My biggest crescent wrench is still to small for the flats on the er40 chuck, and I don't have a proper wrench for the nut. I though it would have come with the collet chuck, but I guess at $40 each, I can't complain
Isn't it funny how quickly one tool purchase can cascade into a LOT of tool purchases?

[Dennis Rech]

Well, no wonder I can't find one... I guess I'm going to have to buy a couple wrenches for my collet chucks. My biggest crescent wrench is still to small for the flats on the er40 chuck, and I don't have a proper wrench for the nut. I though it would have come with the collet chuck, but I guess at $40 each, I can't complain
Isn't it funny how quickly one tool purchase can cascade into a LOT of tool purchases?

If you have a milling machine, you shouldn't have to ever buy flat wrenches again.

It took about an hour to design, fixture, mill, file, and give a touch of the belt sander to make a TG 100 collet wrench out of a piece of 3/16 inch 6061 flatbar.
The best reason to buy a milling machine is so you can make tools for your milling machine.
If you are going to make a ER-40 collet wrench make the handle about a foot long. ER-40 collets need about 80 foot pounds of torque.
store bought wrenches are only about 8 inches at best.

[1HobbyMachinist]

If you have a milling machine, you shouldn't have to ever buy flat wrenches again.

It took about an hour to design, fixture, mill, file, and give a touch of the belt sander to make a TG 100 collet wrench out of a piece of 3/16 inch 6061 flatbar.
The best reason to buy a milling machine is so you can make tools for your milling machine.
If you are going to make a ER-40 collet wrench make the handle about a foot long. ER-40 collets need about 80 foot pounds of torque.
store bought wrenches are only about 8 inches at best.

I guess I could do that. I could make a wrench to tighten my ER collet chuck, which I bought to hold endmills better so I could make tslot nuts and toe clamps for my 3 sine vises so I can make straight edges so I can hand scrape them into master surfaces so I can rebuild my mills so I can begin converting them to cnc. What's one more project right?

Hell, I just started working on a spindle lock since I just can't see paying $120 for one when I've got all the materials just lying around.

Sooner or later I'm going to get to the root of this project...