Stepper Motor Overheating

Hi Folks:

Having received great advice on simple stepper motor control software
I have been trying some out and definetly moving up on the learning
curve.

Recently I have noticed that of the two stepper motors I am currently
testing (Sherlines Shinano Kensi 100 oz holding torque jobbies) one
of them has significantly less cogging resistance than the other. The
one that has less cogging resistance is the one I have been primarily
testing - the other is still basically unused.

Now I understand that overheating a stepper motor will damage it and
I am curious if I have damaged this one. During tests it definetly
got plenty hot - but never so hot that it I couldn't still hold it in
my hand (for a few seconds anyway). Experience with judging
temperature of other devices has told me that if you can hold it in
your hand it is probably still 50 ~ 60 degrees celcius or less.

Is this too hot??
What is the general operating temp for steppers??

I am guessing that either I have caused the permanent magnets to loos
some of their magnetism due to the heat OR everything is ok and it is
normal for the stepper to "break in" a bit.

The motor otherwise still works fine.

Your advice is muchly appreciated.

Thanks

John