View Full Version : Question on ER32 collets

01-04-2005, 04:00 PM
I recently purchased a set of ER32 collets and a collet extension holder to use on my system. Things were working quite well until I pulled an end mill out of the "properly sized" collet :frown: and the question comes up:
What is the "proper" torque rating that should be applied when making this up?

In searching the net, I have found quite a range and wonder what is correct.
Any help will be appreciated.


01-04-2005, 04:08 PM
Damn tight is what I use. Most likely you cannot actually use a torque wrench on it unless you have a special socket to fit the nut. Maybe your collet nut will allow for that.

In such a case, it might also help to carefully degrease the inside of the collet and the tool shank. You can swab the inside of the collet with a Qtip moistened with alcohol or mineral spirits. I don't say that you want the outside of the collet to be that thoroughly degreased when assembling, it may damage (score) when tightened up. Just the natural grease off your hands is likely enough for the outside of the collet.

01-04-2005, 04:18 PM
That is kinda what I have figured. Right now, I "ain't goona tellya" what I am using to tighten the nut with as when I bought the set, the picture in the supplier catalogue showed a hex nut which is isn't(wedge) and I will be making my own cnc'd wrench to fit it and will include a "square" cut out to accept my torque wrench. Once I get a feel for the proper torque, I will put a permenant handle on it.
But, I have seen torque ranges from 40 to 95 ft lb for this series of collet and want to know "what is correct".
I don't want to screw up something like this as they are to darnd expensive!


01-04-2005, 04:18 PM
ER32's are prone to breaking either the cap, the seat or cracking the collet itself. Be careful how tight you make them. Over-tightening them WILL cause them to 1st, crack the seat, 2nd crack the cap-seat, and 3rd gouge/crack the collet.

My rule of thumb, (AFTER I've made sure I can snug the tool in the collet by hand, while not in the tool holder*), is to use a wrench with your hand as close to the nut as possible, and tighten as much as possible. (The further away from the nut, the more leverage, the more torque, the more likely to over-tighten).

I've scrapped thousands of dollars in holders/collets/caps because people use the gorilla-grip to tighten them.

* If you can insert the tool into the collet without force, and pinch it with your fingers enough to feel it 'grab', it's the right collet.

01-10-2005, 01:29 PM

Try using the style of collet nut that has a ball bearing collet race. I believe the Parlec part # is 32ERFN, other companies make them too. These give about 20-30% more clamping pressure at the same amount of tightening torque. It is the only way I would use an endmill in a ER32 collet.

01-10-2005, 05:49 PM
Thanks everyone for your input.

I have now cncd a proper spanner wrench that I put my torque wrench on and find that at about 40+Ft lb, the nut binds so I stop at about 40 and run it!

Right or wrong, that is what I am going to do.

Holand, I just might try one of the ball bearing nuts, but right now, we will see what happens. (Budgets and all that stuff:{(