ER 16 collet size range query.

[Sachakins]

Just got new spindle for my cnc with ER16 chuck.
All sets i have seen, including my own and charts are size range up to 10mm or their equivalent imperial sizes.

Just come across a couple of sellers recently offering 11mm and 12mm.
Anyone else seen these and used this 11 or 12mm collet successfully?

Wonder if there's going to be an 1/2" version? Would be great as quite a few 1/2" ones with my plunge router set.

Cheers

 

[ChaiLatte]

ER collets can be thought of as being invented by RegoFix (the Swiss relation to that fine Irishman Reg O' Fix). Whatever they state in their literature as the range for any particular collet series is how they were originally intended to be used.

Anything exceeding that range is known as an 'extended' or 'oversize' collet, and needs a little care in use as it was not part of the original design. Hence, if one is made, searching for "ER16 oversize collet" would find it.

In particular, you notice that as the collet gets bigger, the part between the tool and the inside of the nut gets very thin, to a point that it can become a razor edge. That greatly reduces the support the collet gives to the tool at that point (maximum bending of the cantilever). It also makes the collet itself delicate.

Hence, you should first measure the diameter of the hole in your ER16 collet nut and determine its difference from 1/2". Ponder on that number and assess the engineering implications. You could also arrive at the same place of enlightenment by looking at the D2 dimension here for an ER16 collet (https://www.arceurotrade.co.uk/Catalogue/Collets/ER-Collets). A third place to measure, if you are not already convinced, is the groove in the collet, that retains it in the nut. Measure its diameter, deduct 1/2" and divide the result by two to give a wall thickness. Assess whether that is reasonable on an item spinning at more than 10 000 rpm.

 

[ChaiLatte]

Should you wish to expand your inner hole, you could purchase one for £0.80 here:

https://www.aliexpress.com/item/1005003775471924.html

 

[Sachakins]

Thanks for this, does make one pause for thought, sounds like having my inner hole expanded is unwise
That Ali link also have a 12.75, so half inch?

 

[ChaiLatte]

That Ali link also have a 12.75, so half inch?

Yes. As you know, 1/2" is 12.7mm so maybe they have made it a smidge larger so the tool goes in easily. If the nose is thin and the collet is exactly on size, you might damage it inserting the tool.

For the price, it is worth a gamble, but use with caution. My general view on oversize collets is that they should be thought of and used in the same way as a space saver spare wheel. Round where I live, that means one on each diagonal corner for six months at a time.