ER11 collets with 1mm range

I've just bought two sets of precision collets from SanTool in Germany - ER11 and ER20.

To my surprise, the ER11 set turned out to be 7 collets stepped 1mm, instead of 13 collets stepped 0.5mm.

The actual collets are marked 7-6, 6-5, ..., 2, 1 - suggesting their range is 1mm.

However, all the ER11 collet sets I've seen in other shops are 13 pieces, each piece having a 0.5 mm range.

I tried to find any info online about existence of ER11 collets with 1mm range, but couldn't.

So, is this really an incomplete set, with improperly marked collet sizes? Or did SanTool somehow manage to beat the competition and provide a superior clamping range in an ER11 collet?

Here's the product page

Edited By Gene Pavlovsky on 09/06/2020 15:17:23

My er11 set also have a 0.5mm range, and because of the small size, I would doubt whether 1mm would be viable. That may be an advantage if they are used to hold milling cutters, as their shanks are normally in 1mm increments, even for intermediate diameters. I would guess that the best fit would be the larger size marked on each collet.

Edited By old mart on 09/06/2020 15:35:48

Is this because the 'end slits' are reduced in number on the reduced collapse ER11 collets - but the German collets achieve the collapsing range of 1mm by maintaining a high number of slits. If so they probably achieve it by using a superior quality of steel in their manufacture.

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Looks like a classic case of a vendor using a generic image and the buyer not reading the description which says they are in 1mm steps 1mm to 7mm, Just look at the parent page and all the sets have the same image. If you want 0.5mm steps then this is the set but I would think lesser quality as price is not much more for almost twice as many collets

As said if you need the half sizes or are going to be closing them down a lot then buy the 0.5mm or imperial as you need them.

Edited By JasonB on 09/06/2020 17:14:36

I don't think they're made in Germany, at this price point.

I did notice the 1mm step in the description, and also the generic photos (really annoying), but ordered anyway. At the moment I don't think I would have any use for the X.5 mm sizes. Hopefully the set will be really extra precision. I've already separately ordered 1/4" and 1/8" collets from China, supposedly high precision ones.

These Fahrion collets look very fancy, for my needs I don't think I need that sort of accuracy, but nice to know they exist.

I will follow the advice and not close down the collets too much (not over 0.5 mm), and will buy intermediate sizes if a need arises. The ER11 and ER20 sets were cheap enough that I think it made sense to buy in sets, they are also small and won't take too much space in storage. I will likely also make an ER32 collet chuck and buy individual collets only for the sizes I need.

Thanks everyone!