View Full Version : Hard Chroming and tight tolerances

July 4, 2011, 01:26 PM

I have a 1911 Gold Cup with minor rust pitting on the slide. I would like to have it hard chromed but am wondering if the already-tight tolerances would allow the extractor, firing pin stop and other parts will still fit as they should afterward.

Does anyone know how thick a hard chrome plating will be and whether that will affect the fit of tight parts?


James K
July 4, 2011, 01:35 PM
Plating will add metal, but the tolerances in the areas you mention are likely enough that the parts can be re-installed without a problem. If they don't fit, you can always take a bit off the parts. If the gun is really tight, you could run into problems with the frame rails, MSH, grip safety, bushing, and interior parts.


July 4, 2011, 01:42 PM
I asked Bob Cogan of Accurate Plating the same question years ago and he told me that the hard chrome layer is typically .001" thick which is not enough to cause any fitting problems on any Gold Cup that I have ever seen. What I have observed is that moving parts with a bead blast finish under the hard chrome can tend to drag when you first assemble them but will smooth themselves out quickly after cycling for a bit. It's kind of like the surface has some "teeth" after chroming which will get knocked down. It will feel a little gritty at first but will smooth out and be slicker than you know what. Don't worry.

Bill DeShivs
July 4, 2011, 02:00 PM
Chrome doesn't plate in holes. It also doesn't plate well in recesses.
Regardless, the buildup should not cause any problems. Tight parts can be stoned if necessary.

July 4, 2011, 02:21 PM
Many thanks. Shall I have the extractor and other small parts plated as well?

Happy Independence Day to all.

Bill DeShivs
July 4, 2011, 03:18 PM
Yes, have the parts plated.

July 4, 2011, 04:02 PM
Thanks, Bill. One last question: Do I have to remove the staked-on plunger tube and/or front sight?

Bill DeShivs
July 4, 2011, 04:57 PM
No, you shouldn't have to.

July 7, 2011, 07:32 PM
I liked reading through this, as yesterday my father and I were discussing some machining projects that we're planning, and he mentioned on certain precision cuts, the anodization was factored into his measurements.

Bill DeShivs
July 7, 2011, 10:28 PM
Anodizing is done on aluminum parts. It does not change dimensions.

July 8, 2011, 07:21 AM
My father is a physicist, and retired with the Dept. of Energy. He built reactors and much of the BNL Accelerator Test Facility. If he says they factored anodizing into their measurements, I'm prone to believing him.

...Not that such a level of precision would be applicable in 99% of machining.

July 8, 2011, 11:26 AM
Anodizing is done by electrically building up a layer of aluminum oxide .Yes it does increase dimensions .

Bill DeShivs
July 8, 2011, 11:46 AM
Anodizing CONVERTS the top layer of aluminum to aluminum oxide. TMK, it produces no significant dimensional changes.

July 8, 2011, 11:54 AM
Aluminum anodizing is an electrochemical process in which an oxide (anodic) layer is chemically built on the surface of the metal. This oxide layer acts as an insulator and can be dyed in a wide variety of colors. Half the coating thickness is build-up and half is penetration into the base metal. Unlike most protective coatings, anodizing permanently changes the outer structure of the metal. When aluminum is exposed to air it naturally develops a thin aluminum oxide film that seals the aluminum from further oxidation. The anodizing process makes the oxidized surface much thicker, up to several thousandths of an inch thick. The hardness of the anodized aluminum oxide coating rivals that of a diamond, enhancing the abrasion resistance of the aluminum. The added depth of the oxide layer improves the corrosion resistance of the aluminum, while making cleaning of the surface easier.

Bill DeShivs
July 8, 2011, 11:56 AM
The dimensional changes should be of no consequence on a gun.
How's that?

July 8, 2011, 11:58 AM
We got wayyyy off topic here. :)