Wristpin finish?

[McRat]

Somebody is pitching wristpins with a fairly high surface finish (16?), and claims that the finish is to retain the oil film.

All the ones I've seen are polished (4, 2?) finish.  I'm thinking poor quality control on the rough pins, not a "feature".

Anyone hear of rough pins being used successfully?

[Dynoroom]

I think you are calling this one right Pat. I wouldn't want serface flaws in my wrist pins.
As for the "oil film" issue, that's why we hone the pin bore of the rods & pistons I thought..... 

[Dean Los Angeles]

A minimum roughness is required on the cylinder wall to retain oil.

The wrist pin is supplied with oil pressure and doesn't need it. Better surface finish means more surface area for the wrist pin to contact with the rod. 

16 is too rough if you are asking me. That's a high end lathe finish.

Lapping gets you down to the 2-4 range, and that's what I would be looking for.

[McRat]

The shop in question claims to be an "innovator", and has "twenty sets" in field with excellent results.  Tastes like snake oil to me.

"No, those tires aren't bald.  That is my new high-traction, low-profile, tread design.  They just look used because I left the door open to the shop and dirt blew inside."

I'm not saying that GM, Ford, Dodge, Honda, Toyota, Kawasaki, Yamaha, etc, know everything, but wristpin surface finish seems to something they all agree on.

[manta22]

In marketing, we used to say "If you can't fix it, feature it"

Regards, Neil  Tucson, AZ

[John Burk]

This is not what you asked but NASCAR cup engines have pins DLC (diamond like carbon) coated and polished by some process . With 6 stage pumps they have no pin galling .

[RichFox]

Back in the good old days when big airplanes had wrist pins we used to chrome plate the pins and then run them through a centerless grinder looking for a 2 finish. I think. It was a while ago.

[Bootleggerjim]

The Nitro bends them, no matter what the finish.....