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raygreenwood
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Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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 Posted: Wed Mar 29, 2023 6:47 am Post subject: Re: Prototype head stud coatings |
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| Ohio Tom wrote: |
I'm on board with high temp paints. I do it often to Raceware studs that come back showing signs of surface rust.
I polish and paint. The come back looking fine.
Also, I have some really expensive race axles on my drag car. They came bare and polished. I just painted them and added stripes so that if they start to twist, I can see it clearly. Easy to touch up if they get dinged..
Nothing wrong with paint... |
Agree.
See, my original suggestion that I have used.....the heavy cold galvanize zinc spray paint....works fantastic if you are trying to protect an expensive, exotic ferrous metal item (that cannot be plated) from rusting. With 30%+ zinc in it.....it protects as well as zinc plating.
However it's not durable. Not because it does not stick or adhere....but because it's very soft and easily scratched. This can be fixed with a fairly hard top coat.
In this application we are speaking of.....where once its assembled and the through holes in the cylinders are clearanced to not rub/chafe on the studs.....you will likely find little or no scratching over time because these are not out in the engine compartment where you are working afound them or removing them all the time.
Any of the gloss or semi-gloss, good quality high temp spray paints should do well as a protective top coat.
Even the Matt paints would be fine but gloss paints are produced using a larger percentage of clear base and had higher pencil hardness.
Yes....an outer hex would be nice for these but flat square would be fine. Ray |
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raygreenwood
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Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Wed Mar 29, 2023 6:58 am Post subject: Re: Prototype head stud coatings |
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| Vanapplebomb wrote: |
I have had decent results with paint on my engine I built a number of years ago. It’s blistering off a little where it meats the threads that I masked off.
Perhaps I should explain my goals for this technical exercise a little bit further.
1) A practical project, as I need shorter studs for my future build.
2) A technical exercise in my spare time at designing something that could be considered a commercial product.
If it were just a simple project just for myself, I would paint them like I have in the past.
But, for the sake of what it is, this will be a step above what I would do for myself.
Hope that makes sense. |
As a design project....at a commercial level.....typically one "might" think about having these professionally zinc plated.....but I do not think this is possible....safely.....or they probably would have come this way from the factory.
Cylinder head studs are similar to CV axles. They are specially hardened and designed to operate with a certain amount of spring tension. Axles operate with a lot of twisting/torsion.
I have read numerous warnings over the eons in various places that scratching/ grinding/ abrading the surface of components like these should be avoided as it creates variations in the surface hardening that propagate cracks. Rust does the same.....Similar to the issues you can get with rust spots on valve springs.
The commercial process for zinc plating high tensile fasteners like grade 8 and class 12.9....is very exacting. The fasteners come from the plating bath and must be rinsed/neutralized in a very short amount of time and go directly into a very controlled, post plating bake to counteract hydrogen embrittlement.
I cannot remember if they get passivated (chromated) before the bake or afterwards.
But the gist is that even with very tight process control there is still some very slight risk of hydrogen embrittlement.
Items that operate under high tension or torque are not risked with plating very often so you see powder coats and paints being used. Ray |
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Vanapplebomb
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Joined: November 03, 2010
Posts: 5418
Location: Holland, MI
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| Posted: Wed Mar 29, 2023 8:03 am Post subject: Re: Prototype head studs |
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Well said Ray! That is exactly why I have eliminated the option of electroplating zinc. Too much risk for me to feel comfortable. Nor do I think it would hold up on the two studs adjacent to the exhaust ports. That is just a hunch, I really don’t know.
As far as spraying goes, I talked to DECC, and they will spray them, as you suggest.
They also offer dip spin, which they say is cheaper because it doesn’t require individual handling of parts. It isn’t as uniform looking, but I guess I don’t really care what it looks like as long as it works.
DECC is a local coater to me. They have a couple products they are licensed to apply, which are similar to the “cold galvanizing” spray paints. I think the biggest difference is the shape of the zinc. It is more flat platelets than powder used in the over the counter spray paints. But, pretty much the same idea.
They recommended using either
-Magni Coatings: Magni 565, which is just a raw zinc flake.
-Doerken MKS coating: Delta-Protekt k120 base coat, top coated with Delta Seal. 2000Hr salt spray rated.
If I were to do a good sized batch, it would likely be cheaper to farm out the coating than use off the shelf cold galvanizing.
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Vanapplebomb
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Joined: November 03, 2010
Posts: 5418
Location: Holland, MI
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| Posted: Wed Mar 29, 2023 8:38 am Post subject: Re: Prototype head studs |
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Now the fun part of milling a hex on the end. Probably try mounting a lathe chuck on the rotary table, and just end milling it. Not very efficient, but it’s all I have to work with.
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Brian_e
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Joined: July 28, 2009
Posts: 3295
Location: Rapid City, SD
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| Posted: Wed Mar 29, 2023 9:01 am Post subject: Re: Prototype head studs |
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| Vanapplebomb wrote: |
| Now the fun part of milling a hex on the end. Probably try mounting a lathe chuck on the rotary table, and just end milling it. Not very efficient, but it’s all I have to work with. |
Use one of these 5c hex blocks. Chuck it in the mill vice, run your flat, spin it, do it again. Super quick and easy.
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Vanapplebomb
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Joined: November 03, 2010
Posts: 5418
Location: Holland, MI
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| Posted: Wed Mar 29, 2023 9:22 am Post subject: Re: Prototype head studs |
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| Brian_e wrote: |
| Vanapplebomb wrote: |
| Now the fun part of milling a hex on the end. Probably try mounting a lathe chuck on the rotary table, and just end milling it. Not very efficient, but it’s all I have to work with. |
Use one of these 5c hex blocks. Chuck it in the mill vice, run your flat, spin it, do it again. Super quick and easy.
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That’s a good idea. I need to get a set of 5C collets anyways for the lathe.
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jimmyhoffa
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Joined: February 16, 2014
Posts: 1059
Location: St. Louis
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| Posted: Wed Mar 29, 2023 9:44 am Post subject: Re: Prototype head studs |
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Take it from me- here's the recipe for buying cheap collet blocks. DO NOT buy the cheapest ones. The way they make those is by taking a piece of bar stock and machining the features on one end for the taper and threads. The reference faces on the outside aren't ground.
The mid-grade Amazon Special ones DO have ground side faces, ground fairly parallel to the axis of the taper. Those are the ones to go for, they're usually about $20 more expensive than the base model ones.
As with most Amazon machine tool accessories: Anti-seize the threads. They aren't very good at alloy decisions/hardness decision making and they tend to self-ruin. ESPECIALLY the ER collet accessories I used to use for CNC stuff. I buy all American/Japanese/German now, or make it myself, whatever it may be. Not interested in giving them money for what I get in return.
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chrisflstf
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Joined: February 10, 2004
Posts: 3446
Location: San Diego
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| Posted: Fri Mar 31, 2023 10:52 am Post subject: Re: Prototype head studs |
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| Have you looked at Raceware studs? They are supposed to be high end parts and at $400 to $500 should be . They use an anti corrosion coating on them, but i dont know what kind. Maybe check it out. |
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Vanapplebomb
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Joined: November 03, 2010
Posts: 5418
Location: Holland, MI
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| Posted: Sat Apr 01, 2023 6:25 am Post subject: Re: Prototype head studs |
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I will probably be using Raceware rod bolts on my next build. Good stuff. Seems they keep their coating pretty close to their chest.
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Vanapplebomb
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Joined: November 03, 2010
Posts: 5418
Location: Holland, MI
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| Posted: Sat Apr 01, 2023 6:26 am Post subject: Re: Prototype head studs |
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| jimmyhoffa wrote: |
Take it from me- here's the recipe for buying cheap collet blocks. DO NOT buy the cheapest ones. The way they make those is by taking a piece of bar stock and machining the features on one end for the taper and threads. The reference faces on the outside aren't ground.
The mid-grade Amazon Special ones DO have ground side faces, ground fairly parallel to the axis of the taper. Those are the ones to go for, they're usually about $20 more expensive than the base model ones.
As with most Amazon machine tool accessories: Anti-seize the threads. They aren't very good at alloy decisions/hardness decision making and they tend to self-ruin. ESPECIALLY the ER collet accessories I used to use for CNC stuff. I buy all American/Japanese/German now, or make it myself, whatever it may be. Not interested in giving them money for what I get in return. |
This is really good info. Thank you!
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