Group buy request/Poll: master cylinder plating for rebuild

[raygreenwood]

As we have several threads going on that concern brake master cylinders:

1. About mods that can be done to use alternate Master cylinders
https://www.thesamba.com/vw/forum/viewtopic.php?t=668756

2. About refurbishing/rebuilding techniques for brake and clutch hydraulics....that this information will be a part of.
https://www.thesamba.com/vw/forum/viewtopic.php?t=674249

The gist of this post is....that the very simplest master cylinder replacement is the stock configuration. But its unique....no longer made, NOS are few and far between and not an acceptable long term alternative......and lastly.....though we can easily rebuild our stock cores by scavenging seals from kits for other cars.......our cores....are either in bad shape or now have been refurbed enough that they are oversized too much.

The master cylinder bore tolerance limit is .004" larger than the piston heads. While the pistons are generally pretty precise....they do have a little variation. I am finding MC and piston sets....where between the piston being about .001"-.0015" undersized...and the bore being close to the high end of its normal tolerance of 19.05mm....the combined tolerance after a very light hone is now above .004"

A good answer to this:

I am getting set up to hone cores out to make sure all rust is gone, acid and caustic treat to totally derust down to bare cast iron.....and then plate the bores with NICKEL.

Nickel is hard and very rust resistant. In fact it will not rust. I can bring the honed bore back up to NEW tolerance during the plating process...then give it a quick hone with 800 grit to put the fine tooth on it.

Then the stock pistons can be rebuilt with seals from cheap NEW kits for type 1 and 3 that are available on Rock auto for about $23. If you do not scratch up the bore....these master cylinders should be rebuildable easily for the rest of your life.

I will also probably put a flash plating (about 1/3 the thickness of the bore plating)...on the outside of the cylinder. So..yes...they will be pretty as well ...not have to be painted ....and will not rust.

It will cost me about $350 to get this set up for plating. So...I will put out a poll to see who is interested in having one or more stock master cylinder cores plated for a low cost to help defray the cost of setting up.

If I can get about 10 people to kick in a little $ and ship their cores to me (I have four of my own to start with)....I am thinking that cleaning, honing and plating for a cost of about $30 each (maybe less depending on interest).....would get it covered. If you have more than one core to plate....it would be something like $30 for the first core and maybe $5 for each additional core just to cover the cost of cleaning chemistry and nickel replenisher.

I am not looking to profit. I am looking to get set up....to do one for my car, a spare or two and to re-plate with nickel my caliper pistons. The caliper pistons were originally plated with either nickel or Zinc-nickel.

I cannot do zinc nickel. It is VERY involved in the control process. Its a combined electroplating and acid plating process.

Electroless nickel.....gives the most uniform plating thickness and surface of any plating. Its only involved in the cleaning and surface prep process (caustic derust, acid dip neutralization, di-ionized water rinse, surfactant/caustic dip, rinse....plate by time and temperature).

If enough people and enough cores get involved it can be made a little cheaper.

Let me know who is interested please. Ray

[titan3c]

Yes Ray, I would be interested. I just recently pulled my mc which has been in the car since new. I can ship it to you anytime. Bob

[raygreenwood]

Thanks Bob!......really hoping a few more want to get on board. I will give it a couple of weeks.


Just to be clear......even if other people don't want to take advantage.....I will at least do mine and yours.

The issue with nickel plating costs.....is batch size. If we get down to the point where its time to get to work and I only have your cylinder and my mine.....I buy a smaller cheaper chemical kit.
To be clear....I will be paying the same amount in for each of my cylinders and caliper pistons. The cost to each person .... is really the cost per unit/cylinder for its surface area of nickel in the process. No labor......no profit.....nothing left at the end.

I already have the heating units, peristaltic pumps, thermometer and glass and enamel vats.

The cost is chemical batch size. With electroless nickel.....a given batch size has only enough nickel to plate so many square inches to a known micron thickness. Replenishment is done by stop watch. If the plating solution drops below a specific percentage of alloy suspended in it.....the solution "crashes".....and must be discarded.....something to highly avoid.

The chemical batches come with a specific amount of replenisher metals and acids. And.....each starting batch can only be replenished a specific amount of times before it must be discarded.

So each kit size will plate X amount of surface area.

Every 30 minutes of immersion at proper temperature will plate between. 0004" and .0005" of nickel.
Most of the master cylinder bores will need a total surface growth of about .0025" to bring them back into spec. Thats about 75 minutes plating.....as each plating of .0005" adds .001" total to the bore.
The bore itself needs that much plating. The outside of the cylinder only needs 30 minutes and gets .0005".
So.....the outside gets masked while the bore gets plated for 45 minutes by itself. Then I unmask the outside.....reclean....and plate the whole cylinder an additional 30 minutes.

I am not starting this to get into the business. The cost covers only batch chemicals.

I plan to plate what I have for cylinders in hand.....two sets of caliper pistons and a small amount of hardware....screws....nuts if I have any batch capacity left.

I figured that once I set aside a day to plate......I may as well help as many people as I can.

When I am done.....I will have master cylinders that will last a lifetime to restore my car with and probably not be doing this again.
Ray