Jicafold

So I have polished like 3 cranksets before with good results. This one I decided to do because there were 2 big marks worn through on the crankarm. However, after removing the anodized layer, and sanding with 150 dry and 320 wet, i still have multiple tiny scratches and pitting. I would need like a file to get them out, which seems drastic. So should I just live with it and continue wet sanding and finishing with Meguirs aluminum polish as I did in the past? What are my options?

HillRider

Some of those marks seem to be from shoe rubbing but others, particularly the small pits, make me think the bike was ridden on salt-treated winter roads.. You could grind and sand them out but I'd be worried that removing too much material will weaken the crank. I'd just live with them the way they are.

dsbrantjr

Live with them. Even MY OCD has limits.

Jicafold

That thought did cross my mind....removing too much material. I'll live with it and finish the process. Thank you.

FlMTNdude

Removing the anodising will make them tarnish easily. You may want to seal them up with a hardened clear seal coat once polished.

capnjonny 

You could also paint them silver or black or , be rad and paint them red. or day glow green!

tomtomtom123

You could try sand blasting the surface with fine grain grit. Then take it to an anodizing shop to get it anodized again, but it would probably be thin layered. Hard anodizing is rare, at least around here. Thin layer is around 20 microns and will easily scratch off. Hard anodizing goes up to 100 microns or more and more abrasion resistant. You're supposed to give it to them clean, so you could wash it in an ultrasonic cleaner first. I don't know if they can plug the spindle hole, maybe they have something that they normally use for plugs. Before anodizing, they will dip it in acid to remove the oxidized layer before dipping it into the anodizing bath. The amount of time in the acid will determine the final dimensions. For example, I've been told that a 20 micron anodizing layer is 10 microns inward and 10 microns outward. And to get a matt finish, I ask them to dip the part into acid for 20 minutes to remove around 40 microns of material. So -40+10 = -30 microns thinner surface. If it were a cylinder, the diameter would reduce by 60 microns, or 0.06mm. If they dip it in acid for only 5 minutes, the surface is semi-gloss/satin (if the part was polished or machine finished, and 1-2 minutes is glossy), and possibly only removes 10 microns, so -10+10 = 0, no change in surface thickness.

However, I've only sent 600 parts at a time for anodizing, which was like 50 cents a piece, for 20 micron anodizing. I've never sent 2 pieces except for a free test trial. So I don't know what they'd charge you for 2 crank arms. It would probably be cheaper to buy new cranks. I think Sugino cranks are around $50 on ebay. Spacycles cranks are even cheaper. I think a complete double crankset with bashguard was $60. The crank arms themselves were less. There are some cheap Shimano riveted cranksets for $30.

Actually, I have a pair of Spacycles 110/74 crank arms JIS 170mm black square tapered that I only used for a few kilometers, before I decided to switch to hollowtech. I kept them in a box thinking I might use them in the future, but I don't think I will. You can PM me if you're interested in them.