ER32 MT2 Collet Holder

I recently purchased a metal working lathe and am quite new to the world of metal lathes.

I've just bought an ER32 MT2 collet holder and ER32 collets from various sources.

My problem is that the clamping nut seems to have an off-centre bearing surface inside it, this I assume is the part of the claming nut that clamps the collets tight. This doesn't seem correct to me as it means that when it is clamped up tight, the top of the collet is well below the top of the clamping nut.

I have bought a collet holder from a Chinese company, a collet nut also from a Chinese company and a collet holder from a well known UK company and the clamping nut has the off-centre hole exactly the same in all 3 cases.

Is this correct or have I been unlucky.

Any comments/advice would be more than welcome.

Thanks, Keith

That is the correct shape for the nut. It allows you to snap the collet into the nut as shown here which will also allow the nut to pull the collet out of the taper in the holder. When snapped into position the end of the collet will be flush with the nut at it's largest size and protrude a little when squashed down.

Thanks, already proving to be a good forum.

Keith

I did exactly the same thing, overtightened and snapped a collet.

The next surprise was finding that collets came in two flavours, accurate and wobbly. Guess which I had

The eccentric flange inside the nut engages the external groove on the collet, and when the nut is slackened, extracts the collet from the 8 (half angle) major taper.

ER collets are very useful, as most have a range of 1mm (0.5mm in the smaller sizes, but not ER32) This allows them to be used for Imperial and metric tools /material without damaging the collet.

If you have a full set of collets, you should be able to cover from 3mm up to 20mm diameter

Unfortunately, unlike 5C, ER collets do not seem to be available for square or hexagon material.

Nevertheless, very useful for work or tool holding.

In Robin's case, I would wonder if the internal retraction flange had been distorted, and was causing the wobble?

Howard