Accuracy of ER32 Collets

[Maurice Cox 1Participant @mauricecox1]

At the recent exhibition at Alexander Palace, I purchased a set of ER32 collets, and a No2 morse taper collet holder. I have just tested five of the collets with a D.T.I. holding ground material. They all run out by about 4thou. I have clocked the internal cone in the holder, and this is out by 4 tenths of a thou, anywhere along the taper. Everything was carefully cleaned before use, including the internal morse taper of the lathe mandrel. Is this an acceptable degree of run out ? I have a limited number of Myford morse taper collets, and these have no run out that I am able to measure. Have I wasted my money? Should I return them as substandard?

Maurice

[Maurice Cox 1Participant @mauricecox1]

[Neil WyattModerator @neilwyatt]

My understanding is that standard (i.e. non-precision) ER25/32 collets should have a runout of no more than about 0.015mm or about 0.0005".

Often when people find their collets are badly out, they aren't properly inserting them into the collet nut. Make sure you 'click' them into the eccentric ring inside the nut and that the front of the collet is more or less level with he front of the nut before tightening them up.

Neil

[Bodgit Fixit and RunParticipant @bodgitfixitandrun]

Have you clocked the lathe internal morse taper to check for runout there? Then work outwards assembling the parts as you go. This should identify if the holder etc is running true and any accumilated error as it is set up.

 

Edited By Bodgit Fixit and Run on 22/01/2015 16:54:28

[Brian WoodParticipant @brianwood45127]

Maurice,

There may be nothing wrong with the collets, in my view it is more likely the chuck is faulty. Do you have a friend who can test them independently for you, or lend you his collet chuck to try them again using that on your lathe? That will be quite revealing.

I had similar trouble with ER25 collets and I finally convinced myself after many tests with loaned gear that it was my own home made chuck at fault. I made another and that was correct.

As Neil pointed out, poor fitting into the collet nut will give 'errors' that big or even more and baffle you by being variable; but your runout test in the chuck bore sounds pretty conclusive, it should be at least as good as the MT taper on your lathe..

[John CParticipant @johnc47954]

Have you tightened them enough? The specified tightening load is quite high! There are tables on the internet. Is the 4 thou runout consistent at all distances from the collet nose?

John

[DustyParticipant @dusty]

Maurice, I go along with John. a simple test is; insert a 20mm collet in the chuck with a length of 20mm silver steel inserted (by about 4&quot and tightened. put your clock on top of the silver steel about 6" from the chuck, with your finger and thumb rock the silver steel in a vertical motion. If you have not tightened the collet enough you will get movement (you will get some movement anyway from bearings etc but that should be no more than a couple of thou) If you get movement try tightening the nut more. It is highly unlikely that you would get a set of collets all with roughly the same error. Remember you are trying to check movement not induce it.

[Maurice Cox 1Participant @mauricecox1]

Thanks gents, all ok now. I didn't appreciate just how tight the closing ring had to be! This purchase didn't get off to a good start, as the morse taper on the holder was so far out, that it would just fall out of the socket. The firm I bought it from changed it very promptly, but it made me doubt the whole set up. Never mind, all fine now, thanks again.

Regards Maurice

[John CParticipant @johnc47954]

Glad to hear it Maurice! I found using a ball bearing closing nut – obtainable from the usual suppliers on here – made tightening much easier.

Here is an example – make sure you get the correct size for your collets!

http://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collet-Nuts-Wrenches-and-Spanners

John

[NJHParticipant @njh]

Maurice

I second John's recommendation of the ball bearing closure nut – money well spent it makes a great difference.

Norman

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