Taking the key way measurement in SolidWorks draw
Hold the shift key while you select roughly the mid point of each radius and it will give you the dimension you are looking for (80mm). As you have probably already found out, selecting the radius without holding the shift key will give you the dimension between the centres of the radius.
Dimension; Condition control.
Answered with a tutorial: https://grabcad.com/tutorials/taking-the-key-way-measurement-in-solidworks-draw
aqui paso a paso
Answered with a tutorial: https://grabcad.com/tutorials/taking-the-key-way-measurement-in-solidworks-draw--1
It looks like you want the center to center distance, say for an endmill, correct?
In any case, the total slot dimension is 80, the radii are 7. There are 2 radii, one on each end, so 80-(2*7), or 80-14=66. If you draw this in Solidworks using a straight slot, the center line is this dimension.
As a dimension in a drawing. Add the dimension as normal - select the two arcs ( it must be the arc and NOT the centre points); then select the dimension so you can see the dimension properties, find the dimension leader position property (second tab I think) and change it from centre to maximum.