ER20 collets on 1/2" and 1/4" bits

**woodPixel** · 13th March 2017, 01:29 PM

I've been thinking about a CNC motor in a lifter for a while. Dale has a thread about it now.

With the CNC it uses ER20 collet sets. They are in metric from places like Hare Forbes.

Does anyone know if they hold 1/2", 1/4" etc imperial bits in the "appropriate sized" metric collet?

I ask as all references say, for instance, 12-13mm or 6-7mm. It is claimed they have a 1mm variance capacity.

Does this mean the 13mm sized collect can hold a 1/2" 12.7mm router bit with confidence?

**Chief Tiff** · 13th March 2017, 01:47 PM

From my previous experience in turning and milling machinery I used ER collets to hold both metric and imperial sized items with no problems. I don't think they make specific imperial sizes; I only ever saw metric and would grab the nearest equivalent. In my last workshop I used ER20 collets in my mill to hole tooling and ER30 collets in my lathe to hold the workpiece.

You could post this question in the metalwork forums if you wanted a definitive answer from someone with lots of ER system experience.

**Big Shed** · 13th March 2017, 02:13 PM

To hold a 1/2"/12.7mm bit you need a 12-13mm collet, to hold a 1/4"/6.35mm you need a 6-7mm collet, and yes they hold these bits very firmly

I have an ER25 set at both my metal lathe and my wood lathe.

Whatever you do don't buy your collets in Oz, they are made in China and much cheaper from Ebay or AliExpress.

**elanjacobs** · 13th March 2017, 07:50 PM

Yes they do work, I do it all the time at work with ER32

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