ER Collets

[Garry Coles]

Hi everyone
I have a MT3 collet holder with various ER metric collet sizes, and what I want do is buy some ER imperial collets. The problem I have is not knowing if I have ER 11, 16, 20, 25, 32, 40 or 50 size. Are these numbers related in some way to the dimensions of the collets.
Thanks

[SteveW]

Garry,

I just looked at my two ER32 collet holders the ER32/R8 kit from Chronos and the ER32 face plate collet from Warco. The easy answer is that the open end of the taper is 32mm as best I can measure. I guess it follows the others follow a similar rule.

I was attracted to buying the ER range over the more 'normal' type because each can cope with a range of one millimeter. This I interpreted as meaning that providing the collet is no more that 1mm larger than my imperial stock it'll close securely on to it.

The kit gives me collets starting from 3-4 through 4-5, 5-6 up to 18-19, 19-20. I've just noticed that some are dual marked imperial/metric.

Hope this helps.

[3405jimmy]

Sticking ER collets sizes in Google came up with a forest of answers. Take a look at this link and page down it gives the OD and length of the various ER system collet sizes. I expect you should be able to identify which ER set you have from this

www.usshoptools.com/current_year/all_products/2005_06_pdf/PGS_491_493.pdf

Jim

[Tim Bayliss]

As Steve correctly noted ER collets, regardless of their size, are (or should be) marked in both metric and imperial, there are no dedicated metric or imperial ones, they do both.
Axminster.co.uk seem to be about the cheapest I've seen to get a few extra collets but their fitting size range is limited (ER20, 25 & 32 only I think).
Regards,
Tim