Powder Coat Backing Plates?

[John R]

I decided to splurge and have my nice 46-48 backing plates powder coated. However, the powder coater says the adjusters will become frozen and unmovable afterwards. Can anyone verify or refute this statement (based on actual experience) or provide other relevant refinishing info?

[flatheadfan]

Yup, I agree with your powder coater. I had a similar experience and the part became useless.

Tom

[Kurt in NJ]

At the least it will chip when enough force is used to break them loose ---I have had to work on other things that were powdercoated and threads needed tapped so bolts would go in, and moving linkages were siezed up

I have seen powdercoated wheels make a freshly trued brake drum more than .005 out of round ---and then go back to true after the powdercoating was sanded off where the rim contacts the drum.

When I painted my Citroen backing plates I first primed with epoxy , then moved the adjuster to prime the areas un-covered ---even the epoxy primer tried to stick the adjusters in place

At least he is telling you what will happen, much better than finding out later that they are stuck and won't move

[Pete Fl/Wi]

My new backing plates came with instructions "fitting problems have occured with powder coating" painting was recommended.

[Kube]

Okay, I have restored five cars in the past six years... each one has powder coated backing plates. NOT one single plate (20 plates) has had any issues with the adjusting bolts.
It took very little force to loosen them. Once loose, they work just fine.
A good powder finisher should work with you to understand which holes should be covered (not powder finished) as well as threaded studs, holes, etc. Any surface can be taped off.
Drums? Yep, I've done a lot of those as well. NEVER a problem.

[Fe26]

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As far as potential warping is concerned, particularly on thinner parts, if a part has an area of in-built or acquired stress which is stable within the part ie: present but not apparent, then the Powdercoating process (heat) is above the temperature required to release those stresses.

Obviously if the part is not stressed then there won't be a problem, and the opposite is also true. As far as threads etc. are concerned, they can be shielded by Allfoil.

[John R]

Thanks for your replies. Although there isn't a consensus on backing plates, it's clear that some caution and forethought is needed when powder coating.

[itsa52]

They can mask areas and plug holes before spraying the powder, which will eliminate any of these problems..If you put a bolt in a threaded hole they need to remove it before the powder cools, but it is done all the time.. Wooden plugs or dowels sanded to fit work great.

[John R]

Originally Posted by itsa52

They can mask areas and plug holes before spraying the powder, which will eliminate any of these problems..If you put a bolt in a threaded hole they need to remove it before the powder cools, but it is done all the time.. Wooden plugs or dowels sanded to fit work great.

Yes, my powder coater (a large industrial company) always goes over each item with me regarding any areas needing masking, such as holes, gasket surfaces, studs, etc. (They use very special masking tapes that will survive media blasting and powder curing temperatures.)
The adjusters in a backing plate are a little different. Would be nice to have those parts coated, but at least the part on the outside (spring and hex-headed stud) could be easily masked and painted afterwards. The inside part (cam) is a little more problematical.

[hotcoupe]

i went with option #2, stripped backing plates of all hardware. powdercoated the plates, machined new adjusting bolts, cadmium plated all hardware and then re- assembled the backing plates. i think the hardest part was finding the 11/16" wrenching head bolts with a thick head. i am re-furbishing and up-grading a `37 1/2 ton.
tom