Handle Fit Calculator
Nobody sells a handle that fits. Blanks are cut oversized on purpose and the eye they have to fill was drifted to a pattern nobody publishes any more, so a rehang is four measurements and a rasp — eye length, eye width, eye depth, and the tongue that has to go into all three. Put your figures in for the stock to take off each face, the depth to saw the kerf and the wedge that closes it.
Units
The eye
Measure the opening at the top of the head — the wide end the tongue is drawn up into.
The long axis, poll to bit.
The short axis, cheek to cheek.
Top of the eye straight down to the bottom.
The tongue
Measure the blank across the point that will finish level with the top of the eye, not at the shoulder.
Same axis as the eye length.
Same axis as the eye width.