Hub cone nuts. Why do they crack?

is the frame actually 130 spaced or is it a little smaller and putting a lot of pressure on the nuts?

edit: they crack because they are a harder steel to actually grip. thus making them a little more brittle. if they were softer they wouldn't break as often (its pretty common), but at the same time they also wouldn't bite in to your dropouts to hold your wheel in place.

Good info. Thanks.

It's is a 130 spaced frame and not pinching much. Being an old road frame the dropouts don't have the large flat area of track ends. Perhaps this is focusing the pressure a bit.

because....
cheap metals
bad thread on axle
dirt on threads on axle
too much force
wrong tool
erm, a combo of the above?

I used a cone spanner and didn't go nuts (ehem) with it. Might have over done it tightening the track nuts though.

I have had this problem too, your lbs should stock spares.

I'll pay them a visit. Time off the bike though! Very frustrating at this time of year.

Cheers for the comments/help.