cyclotoine

Martin Trautmann posted on rec.bicycles.tech:

L_right = 18 +0.5/-0 mm
L_left = 16 +0.5/-0 mm
Dimension across flat 1.5 mm from end: 12.6 mm +0.02-0.05
Spindle end to bolt seat: Loose: 3 mm
Tightened: 1.5 mm min.

Yet another source claimed that the squares of Campa, Mavic and
Stronglight (ISO) are smaller than Shimano and Suntour (J.I.S.) with the
result that J.I.S. cranks will move about 4.5 mm further in.

This may conflict with the end of the square and result in a loose fit
or braking stress. for ISO cranks on J.I.S. squares there's less contact
area between crank and spindle, since the crank does not slip perfectly
on the spindle. The result again is a higher risk of braking the crank.

But assuming those 4.5 mm and 2 deg, ISO is about 0.3 mm smaller than
J.I.S. (2 * sin 2 * 4.5 = 0.3)?

ISO cranks (Campagnolo, Stronglight, others) won't go as far onto J.I.S. spindles as they ideally should.

J.I.S. cranks (most Japanese models) may bottom out if installed on ISO spindles.

In practice, you can very often get away with mixing these sizes, as long as you select an axle length that gives the desired chainline.