Hi All:
Just for curiosity's sake I grabbed a couple of DME and National pins I have in stock and checked them under the microscope.
The DME pins are centerless ground and the grind marks are clearly visible.
The National pins are old old stock, and they show centerless grind marks too, but they look to have been electropolished as Paul says.
Super premium pins such as are used for very tight clearance applications like molding nylon Santoprene or LIM rubbers may well be lapped; I don't have any around right now, but I know the Royals we used to use in a toolroom I worked in many moons ago were dead nuts accurate within a tenth over their whole length.
Even then, there were applications where we had to wire the holes, then lap them and then select the best fit pin for each hole and mark it to only run in that hole.
The running clearances were microns, and everything had to be just right or the ejection system would pick up and jam and it would be an expensive mess to fix.
LIM molds were the worst...fussy as hell because you had to be able to pull a vacuum in the cavity, but I digress...
Back to the OP's inquiry, if you are seeing evidence of draw polishing on the pins you're referencing, they could either be lapping marks or wear marks.
I've never looked at a high accuracy pin under the scope so I don't know.
Cheers
Marcus
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