Im unsure why your cut depth is that. All our Hobs we use to cut L is .083" depth so the 2.13mm. IP-24 is the standard for this pitch and it shows the 2.13 if you need a reference to that dimension Yours could be to some euro standard maybe DIN? Or another thing it could be a non-topping style...
there is a standard available for taper locks MPTA-B9i-2013. heres a link to it. http://mpta.org/wp-content/uploads/2016/05/MPTA-B9i-2013-TL-Bushing-Standard.pdf
