@jwilo Divide your M92 steps per mm by 360, then one millimetre of movement will equal 1 degree of rotation; ie

M92 A2.222Rotational axes are effectively treated the same as linear axes, unless you make use the M584 S parameter to control the feedrate; see section 2.1.2.5 of the NIST GCode standard for how the feedrate is interpreted in this instance: https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=823374

2.1.2.5 Feed Rate

The rate at which the controlled point or the axes move is nominally a steady rate which may be

set by the user. In the Interpreter, the interpretation of the feed rate is as follows unless inverse

time feed rate mode is being used in the RS274/NGC view (see Section 3.5.19). The canonical

machining functions view of feed rate, as described in Section 4.3.5.1, has conditions under which

the set feed rate is applied differently, but none of these is used in the Interpreter.A. For motion involving one or more of the X, Y, and Z axes (with or without simultaneous

rotational axis motion), the feed rate means length units per minute along the

programmed XYZ path, as if the rotational axes were not moving.B. For motion of one rotational axis with X, Y, and Z axes not moving, the feed rate means

degrees per minute rotation of the rotational axis.C. For motion of two or three rotational axes with X, Y, and Z axes not moving, the rate is

applied as follows. Let dA, dB, and dC be the angles in degrees through which the A, B,

and C axes, respectively, must move. Let D = . Conceptually, D is a

measure of total angular motion, using the usual Euclidean metric. Let T be the amount

of time required to move through D degrees at the current feed rate in degrees per

minute. The rotational axes should be moved in coordinated linear motion so that the

elapsed time from the start to the end of the motion is T plus any time required for

acceleration or deceleration.

Ian