[Ken_Shea]

I need to modify the end shaft diameter on a small servo and have heard that it can weaken the magnets if the armature is removed thus causing performance degradation .

Is this something I need to be concerned about ?

Thanks
Ken

[Al_The_Man]

It depends somewhat on the composition of the magnet, most types in recent years have used very high residual composition (samarium e.g.) and do not lose anything when dissasembly, with samarium though it is very brittle and call spall easily, The main problem I think was with the older ferrite etc materials.
Personally I have dissasembled both DC and AC servos for armature work, and have never yet had a problem, you could slide a 'keeper' bar behind the rotor in the case of DC for e.g.
I also have several large stator magnets from scrapped motors I use in the shop for various temporary holding devices and these magnets still require heck of a force to remove when done.
Al.

[Ken_Shea]

Thanks,
Sounds as though there is little risk, I will give it a go.

Ken

[ESjaavik]

In my experience: yes be concerned.
I made a DC servo into junk taking out the armature. And the performance is not just degraded, it's more or less completely gone.

It is as Al write very dependant upon what kind of magnet is used, but do you know what it is in your case? Maybe I was just unlucky, so I tried it again on some steppers that were not suitable anyway, and guess what! More junk...

So, I just don't do it any more.