Axle plating

[Ickabod]

Since the BSA axles are zinc plated steel nails, after de-burring the nails and polishing with 2000/4000/8000/12000 grit paper, are you getting rid of the zinc and down to the steel? How thick is the zinc plating? Has anyone else wondered this or experimented with this? Has anyone done a cross-section analysis of an axle?

[FatSebastian]

How thick is the zinc plating?

This is an interesting question. The actual plating thickness would depend on the type of plating process employed for BSA axles (e.g., electroplating v. mechanical plating). ASTM International plating classifications start around 5 to 8 microns (0.2 to 0.3 mils), but very light-duty / indoor applications could be as thin as 1 micron, all of which is below the measurement precision of most calipers. One needs a pretty good micrometer to detect changes in material thicknesses at that level.

after de-burring the nails and polishing with 2000/4000/8000/12000 grit paper, are you getting rid of the zinc and down to the steel?

We've always presumed that deburring / ridge-removal exposes the steel underneath. Note that 12000 Micromesh cuts / polishes to 2 microns, and most steel is two- to three-times harder than pure zinc so the plating wears away faster. Not being sure what kind of sandpaper is being described here as "...12000 grit paper", this chart may help compare finish smoothness with any presumed plating thicknesses.

[FatSebastian]

I'll add that MaxV suggests that his zinc-plated speed axles can be polished out with the "the two finest papers" of his Axle Polishing Kit, advertised to be at 5 and 3 microns. So the zinc plating on those axles would presumably be thicker than that.

For someone with a precise micrometer, it might be an interesting experiment to measure a raw axle with a micrometer before and after the zinc coating has been removed. For example, might one heat quench the axle to remove the plating, and then remeasure? In principle, the difference in the micrometer readings should be twice the plating thickness.

Perhaps a vendor who supplies axles can comment on what plating thicknesses are typical. (Sporty also has some experience with respect to industrial plating.)

Some people think removing the zinc is advantageous.

[Ickabod]

Thanks Sabastian! Great information. This will help in my experimentation with different axle polishes. Now I can focus more on a steel polish vs one for zinc (if there is such a thing). I am hoping to find some obscure, little known polish that will work better than whats commonly available, but I am afraid that doesn't exist based upon all the great builders that are out there in the PWD world. At least it gives my sons and I something to explore and learn about the scientific method.

[sporty]

I have never ran into polishing into the stock bsa axles, past the plating.


I was actually a plating line operator back in 1997-1998. I did dull nickel and bright nickel, door hinges for lawernce brothers, now defunk.

I used dip tanks, however, for items like nails, they use a barrell line to plate them.

And here is somethings, that play into the coating thickness.

1-how clean the tanks car.

2-how clean the axles get, before being plated.

3-how well they tumble and get mixed up as they get plated. Meaning if they are over filled or under filled. even tho the plating time changes, it effects the thickness of the plating.

Then there is out variables, how consistent the steal is, ffrom the batch of rod they used, to make the nails.

Other weird variables, people running the show on the zinc balls, to the chemicals in the tank, and the cleaning tank.

Depending on what there flex ability is for quality, will determine how thick or how even and good of a coating you get.


often, due to cost. they dont put in new chemicals or zinc balls, until its pretty bad. And the cleaning tank. dont seem to get changed out as often as they should.

A cleaing tank, is a acid mix, that rinses and eats a light layer on the surface of the metal, oil and dirt come of and the surface now can provide a good electric contact surface for plating.
Id about bet, they never check it with a micrometer. we never did, but they were only hinges.
But I would bet, that the plating thickness ranges from 3 thousandths to 10 thousandths thick.


Sporty

[Kenny]

I played with copper/nickel and chromium electro-plating...the latter interesting because of hardness. However the chemical hazards were not worth it. Cost was high. And, like shorty points out imperfections were difficult to eliminate.

What I was REALLY interested in was a tungsten carbide axle set, but never was able to make that happen. Always thought the weight would be advantageous too for a couple reasons.

Truth is, good clean aftermarket axles, properly prepared, are really impressively smooth when viewed under an electron microscope.

If you are going to plate, then...
Nickel is nice. Chromium is nicer

K