How tight is the collet nut suposed to be fastened ? I am worried about damaging it and I am considering a torque wrench.
Has anyone a recommendation ? Thanks!
A standard ER-11 collet nut will be 20-22 ft-lb (27-30 N-m). Some discussion with links to backup documentation is at http://bbs.homeshopmachinist.net/threads/38649-ER-Collet-nut-torque .
Randy
Thanks a lot Randy! I did not think about that. 
So 20-22 ft-lb is a max value. Following the reference links (mostly broken) in that thread, I found that Vortex recommends a little less:
-8<–
*Recommended torque is 80-90% of max value.
-8<–
I have made a lot of research on a torque wrench open-ended or box-ended but I can only find massive wrenches (for engines) on common web sites. Would you have a recommendation for a proper wrench to go with the Nomad collets ?
Anyone with shop recommendations for Europe (Belgium or France) ?
P.S. I am actually willing to calibrate my fingers but I need to set reference points. I have no clue what 20 ft-lb feels like; even less so with palms up or using a short wrench in a tight space. 
I think the right answer would be “comfortably snug” but you don’t have to crank on it. You’ll start to feel where the stop is when the collet doesn’t want to tighten any further because it’s in full contact with the tool shank. You don’t need to push it much past that.
You’ll note when you go to take tools out that there is a tight/loose/tight/loose again torque response as you unscrew the nut, as the collet “sticks” a bit to the tool. The tool is still fairly tightly held until you pass that second sticking spot. Once you get past that, the tool will fall right out, so on expensive micro tools be ready to catch them!
Thanks! It is precisely this tight/loose/tight/loose torque response while unscrewing that got me worried. I thought I was going too far.
So I am taking that, in a reverse way, I need to apply just enough force so that when unscrewing, I get “tight/loose/tight/loose”, no less.
Also, I am using two wrenches. The black one provided with the Nomad to hold the nut and a #12 to hold the spindle. I am not suppose to hand-tighten it, am I ?
you’re spot-on with the two wrenches, you just don’t need to get out the elbow grease 
I don’t know how much torque exactly, but if you’re concerned you will strip the wrench or nut, you’re tightening it too much.
Hopefully someone else can chime in here with a more precise answer on what that feels like!
1 Like
I don’t have a Nomad (I’m just here for the MeshCAM ) but on ER-16 collets (next size up) I use wrenches that fit the flats, put them close enough together to grab with one hand, and squeeze as tight as I can out near the end of the wrenches. I have never had a tool come loose doing that. Wrench lengths vary pretty proportionately with the size, so it should work the same for ER-11. Same force, smaller lever arm.
The reason for tight-loose-tight-loose is that the ER taper is self-locking. The first tight is loosening the nut from being tight, then loose as it backs off until the ledge in the nut touches the other face of the groove in the collet, then tight as it pulls the collet loose from the taper.
Randy
1 Like
Thanks UnionNine and Randy.
In the light of your explanation, I think I did it right (not too hard, not too weak). In my ignorance, I felt the tight/lose/tight/lose was abnormal and that maybe I was still being too hard. Nothing to worry about then. It is good to understand the feeling of the mechanism.
Thanks again for your help. You spared me a torque wrench.