cutter slippage using ER series collets

It is very important for the cutter body, to have the full length of engagement in the collet itself. If the cutter is 3/4 of the way in the collet body, there is a high probability of it walking out on a big cut for sure . The thinner wall collets require the full length absolutely. It is for this reason that I have different collet sets, with the smaller series collets for holding the smaller cutters. Cutters with a 4mm shank or smaller I use the ER11 set. For 10mm to 5mm I use the ER16 set and for over 10mm use the ER32 set or ER40. Hanging onto a cutter with less than 1.5 diameters is never a good idea , so then you are better off buying a longer series cutter.

Using a pair of tools to tighten the collet nut is a zero torque arrangement and you can get a lot higher closing pressure instead of using just 1 tool and locking the spindle or 1 tool and a bench holder.

Neil

You'd need to explain that further for me.

Well, I hadn't heard of ball bearing nuts, so I did a google, and found an interesting video showing the difference.

**LINK**

So now I guess I will have to buy a new nut for my ER32 set!

John

+1.

Thank you, concur.

Threaded shank Clarkson tooling is not guaranteed foolproof. They can snap at the point where the thread meets the shank, it has never happened to me, but I know toolmakers and millers who know better.

So when you have a spanner holding the tool body, and a spanner holding the nut, as you bring the two tools together , there is no twisting moment on the spindle. As you bring both hands together, you can get them a lot tighter than just trying to pull on 1 lever. Mechanics do this all the time on fittings. The same in reverse, you an pull the two levers together to undo very tight fittings.

But what if you can use two hands on the one lever while the holder is in a bench fixture and get your weight behind it?

Yeah I would think that it would be tighter. But in the machine, using 2 levers I think is the better way to tighten the ER collets.

or better still both feet on the bench and both hands on the wrench (or was that wench) ;O)

Martin

Thanks for the help. I did not know you could get ball bearing nuts so i am going to order one from Arc Euro trade.

Also suggest buying the larger 4 point spaner from Arc euro. When using er40collets to hold large Whitworth taps,I admit that I do use a length of tube to get them really tight,I am well into retirement and so not as strong as I once was and if I damage a collet ,so what they are cheap and the customer pays for his Whit nuts. When working on full size thick wall copper steam pipe,the er40 collets grip the soft pipe without damage and allow threads to be cut with a die.

I believe the handle of my ER25 spanner is about 25 centimeters long. I don't really have to give it more than a good normal drag, and I can't remember having had a problem with the cutters going anywhere. (If more torque were needed I figure they would have made the spanners longer - just as the length of normal spanners standards are adjusted to the respective corresponding bolt/ nut torque requirements).

Ball nuts do increase the grip, but I never have a problem with the normal nuts either. I do have a bench holder and that helps of course.

I suspect the problem might be that the cutter is not perfectly centered in the collet. An indication of that might be that the gaps at the top are not evenly sized. Common causes of that is for instance putting the collet into the tool holder before putting on the nut, not tilting the collet over the lip inside the nut, overtorque or simply a cutter size outside of the collet range.

If it isn't any those I think I'll place my cents on a bad collet. Blame the tools

Edited By Vidar on 05/10/2019 20:02:02

Hi I bought the ball race nut, the spanner and an imperial set of collets from Arc Euro, all for £50 including the post. I got them the next day and am very pleased with them. It's much easier to tighten and loosen the nut now. So I hope that solves the problem.

All good then

The thread just seemed so focused on torque. The issues I've seen have typically been more about less than ideal assembly or simply swarf. So I thought I'd add those to the thread as ER can be finicky.

Edited By Vidar on 05/10/2019 20:52:21