Stop in for a cup of coffee

toolmanmike said
Those look good. Metal will last forever. Nylon not so much.

I have a few nos nylon ones and they are also brittle as hell, I try not to use them at all any more, would really suck having one break in a motor, and I am sure they did. Prob 1/4 of the cores I have do not have them anymore, some have half.