Model A lock washers

[glenn in camino]

I just had a bunch of stuff cad plated. While sorting everything out I got to looking at my lock washers. Most are serated on the outside edge similar to a dime. many others are serated with various patterns mostly on the outside edge but sometimes on the inside edge and sometimes on the face. Are they all Model A or are some from different cars? Also, are lockwashers judged in the blue ribbon class?

[BRENT in 10-uh-C]

I think the different patterns were different suppliers. Yes lock washers are judged in fine-point although most were unfinished on the undercarriage.

[Marco Tahtaras]

As Brent said, it was a matter of supplier. That isn't to say all you have are originals without seeing them. The straight serrations were the most common for SOME sizes and uses.

Now that you've had them cad plated let's hope the plater did the full process and properly baked them or they will be prone to failure from hydrogen embrittlement (ruined). The same issue applies to acid dipping them to strip off the cad plate.

[RockHillWill]

Hey Marco, explain that some more. I was under the impression that hydrogen embrittlement was only associated with the process required for chrome plating. In my previous endeavers we could not use chrome plated items, but was not aware of any issues with cad plating. can you elaborate?

I am working on a project where this might be an issue .

[Tom Wesenberg]

Originally Posted by RockHillWill

Hey Marco, explain that some more. I was under the impression that hydrogen embrittlement was only associated with the process required for chrome plating. In my previous endeavers we could not use chrome plated items, but was not aware of any issues with cad plating. can you elaborate?

I am working on a project where this might be an issue .

I've had a problem with some bicycle spokes breaking, and was told to try to find spokes that are NOT cad plated, for the reason Marco mentioned.

[Marco Tahtaras]

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Originally Posted by RockHillWill

Hey Marco, explain that some more. I was under the impression that hydrogen embrittlement was only associated with the process required for chrome plating. In my previous endeavers we could not use chrome plated items, but was not aware of any issues with cad plating. can you elaborate?

I am working on a project where this might be an issue .

I don't know what acid is used in the process but that is basically the cause. That is why lock washers are rarely cadmium plated. Have you ever seen replated spark and throttle control links at a swap meet only to find the internal end springs weak or broken? This is an example. Maybe someone here with a background in plating can explain the process including the proper timing and temperature they need to bake the items to circumvent the problem when plating tempered steel.

[RockHillWill]

Thanks for the heads up Marco. I will look more into it before I get to far into this project.

I sure did remember that you do not want chrome plated suspension parts on a high performance 'ride' but thought that it was a combination of the temperature and chemicals process for chrome plating that brought about the hydrogen embrittlement problem.

Thanks

[RockHillWill]

Called the guy that does my plating and asked him to elaborate.

He said that the concern about hydrogen embrittlement is aplicable to all/most forms of plating including both chrome and cadmium as well as nickel and copper. When water is given an electrical 'stimulus' it provides VERY small hydrigen bubbles that seek to attach themselves to the anode (part). It is generally counteracted either by bubbling the solution, vibrating the tank or cycling the rack that holds the parts being plated.

It is not applicable to aluminum parts, but seems to be more of a concern as the quality of the metal increases, so that it might be a concern on VERY high speed / stress vehicles, but is almost a non-issue with components used on cars that we work with.

Apparantly all platers have addrerssed this for a long time.

[peters180a/170b]

For over 35 years i never had a lock washers snap[break] because of Cad, plating. I did however lost some when i used Metal Prep. and soaked them over nite. Now i wire brush the washers clean until mint and then quickly run them thru Metal prep and then run them thru paint thinner. Then blacken or Cad. plate after.

[Terry, NJ]

Marco, Aren't lock washers hardened and tempered? When you "bake" them doesn't this affect the temper or the hardness? Just wonderin"
Terry

Originally Posted by Marco Tahtaras

I don't know what acid is used in the process but that is basically the cause. That is why lock washers are rarely cadmium plated. Have you ever seen replated spark and throttle control links at a swap meet only to find the internal end springs weak or broken? This is an example. Maybe someone here with a background in plating can explain the process including the proper timing and temperature they need to bake the items to circumvent the problem when plating tempered steel.

[BILL WILLIAMSON]

Years ago, workin' on Jaguars, lots of chromed wheel spokes broke at the big end. Then they stopped chroming the last 1" of the big end & just painted the end with aluminum paint, NO MORE BREAKAGE! Bill W.

[glenn in camino]

I've been working on Model As for over 40 years and have never broken a cad plated lock washer, although I do believe the experts. I know they're not correct in many places but they sure look nice and I don't think I'll loose very many points. Besides I'm usually in the touring class.

[Marco Tahtaras]

Originally Posted by Terry, NJ

Marco, Aren't lock washers hardened and tempered? When you "bake" them doesn't this affect the temper or the hardness? Just wonderin"
Terry

It's a relatively low temperature. It turns out to be 375 degrees Fahrenheit on average.

Originally Posted by RockHillWill

Apparantly all platers have addrerssed this for a long time.

My experience conflicts with that statement. Platers typically talk a good story however. I'll tell you up front that what little I know came from Doug as he's had to deal with this stuff for years for aircraft engines. Here is an excerpt from a document I found:

Even when hydrogen pick-up is minimised during surface finishing, removing hydrogen that has diffused into steels by subsequent baking at low temperatures (< 205ºC) is generally specified. Recommended baking times and temperatures depend on the finishing process and, for electroplated components, also on:

1) The type, thickness, and porosity of the plate.
2) The strength of the steel.
3) Whether components are sharply notched (or threaded), notably bolts and other fasteners.

Examples of recommended times and temperatures are:
1) For porous cadmium-plated high strength steels: from 23 up to 40 hours at 190ºC.
2) For nickel- and chromium-plated steels: from 3 up to 12 hours at 190ºC.
3) For pickled and cathodically cleaned steels: 3 to 4 hours at 175 – 205ºC.

Baking specifications also indicate that it should be done as soon as possible after plating (typically 4 hours), since excessive delays (> 16 hours) between plating and baking can cause irreversible embrittlement (cracking), e.g., in ultrahigh strength 4340 steel with a tensile strength range of 260 – 280 ksi (1790 – 1930 MPa). Note also that baking at low temperatures can remove hydrogen only from interstitial sites and weak traps such as dislocations and grain boundaries. Hydrogen remaining in deep trap sites such as voids at inclusion-matrix interfaces and between steel surfaces and plating, see Figure 20-1, can diffuse into the steel when sustained tensile stresses are applied, thereby causing some embrittlement.

Now I suspect the biggest problem with cad plated OLD parts is that to achieve a good clean finish the parts are pickled which is an issue all it's own as noted above.