SK40 collet holders - purpose of V-notch

Can anyone please enlighten me as to the purpose of the V-notch next to the drive dog slot on SK40 collet holders (DIN 69871)? And while we are on the subject of SK40, what is the benefit of having one dog slot being 2.2mm further from the centre of rotation than the other opposite? Thanks

Edited By Adam Harris on 20/02/2023 23:56:18

That style of holder is generally used with an auto tool changer, so the features you see probably relate to that part of its operation.

The tool changer arm needs to grip the holder and possibly orient (clock) it. On something with 360 or 180 degree rotational symmetry, that would be difficult.

Just to follow up, Haimer, who should know a little about these things suggest that DIN 69871 is now superceeded by DIN ISO 7388-1 and call it "SK40 form AD/AF DIN ISO 7388-1".

https://www.haimer.biz/products/tool-holders/din-iso-7388-1-sk304050-formerly-din-69871.html

Thus, some information on the function of the notches might be found in that Standard.

There is a legitimate preview of the Standard (i.e. not some dodgy copyright infringement) here:

https://cdn.standards.iteh.ai/samples/44098/5e966b98c6c64a15ab24719cc9f3dc47/ISO-7388-1-2007.pdf

Many thanks DC31k - I have just contacted Haimer via online chat and they were fast and very helpful. The V-groove is called a German Slot and is for alignment in the magazine of CNC machines, and the thick part inside of that dog slot that is further from the axis of rotation (and which prevents the SK tool holder from fitting the dogs on a spindle set up for ISO or BT holders (requiring dog or slot modification) is to hold an RFID. Standard production of these holders do not have an RFID inserted but machine manufacturers can have them inserted to allow the machine to recognise attributes of the tool such as type, height etc.. Interesting. Adam

Edited By Adam Harris on 21/02/2023 11:18:02