case hardening question

[Long John]

If I brown a lock now and later decide that I want to case harden it will I be able to case harden the lock in the browned state or will I have to remove the brown finish first?

thanks for your input.

Best Regards,

JMC

[Michael]

My guess is that at the temperatures needed to case harden the steel/iron would assorb the carbon right through the brown (rust) finish.

Interesting question! Sure would make any polishing of the lock in the future a PITA.

Michael

[JCKelly]

Clean off te rust first. It will just slow down the case-hardening process (the carbon will first have to reduce that iron oxide to metallic iron, before it can begin diffusing in to the metal).
Also I suspect you would get an unatractive rough surface.

[smart dog]

Hi John,
I would clean the finish off.  If you just want the plate to be hardened, it probably won't matter too much if the old finish is still there and you don't need to polish the surface very much.  However,  if you want nice colors you must clean off the finish and polish the plate.  The higher the polish, the more vivid the colors.

dave

[Dphariss]

If I brown a lock now and later decide that I want to case harden it will I be able to case harden the lock in the browned state or will I have to remove the brown finish first?

thanks for your input.

Best Regards,

JMC

I would case and then brown if  I wanted a brown lock.
I would not case a browned part would repolish first.
Dan

[westbj2]

The consensus among those who do commercial color hardening is that a 400 finish on the metal results in the best colors.  I have had color hardening done over a 600 finish and found that the colors are somewhat more subdued than over 400.  Best to check with who ever is going to do the work for you as to their recommendations for surface finish.  This "black magic" of color hardening varies by the specific process used.
Jim Westberg

[Dphariss]

I generally do 600 then 0000 steel wool with chrome polish to even the finish, this just removes the odd "scratches" and brightens it somewhat. I would never do less than 400 for color hardening. Better polish give better, brighter colors and sharper definition of the colors.
But as Westbj2 mentions it can vary from batch to batch, who does the hardening and the steel alloy can change the colors as well at times.

If polishing for an engraver 400 may be enough some engravers do not like a really high polish. It makes the surface too bright and makes it harder to draw on etc.

Dan

[keweenaw]

Doug Turnbull recommends polishing to a worn 400 finish.  If you plan on color hardening later don't do a brown that pits the surface.

Tom

[JCKelly]

Part of the "magic" of color case hardening is to pack it in bone charcoal, or some mix of bone and wood charcoal. It is the calcium phosphate in the bone that does the magic coloring.  One might also get some calcium phosphate (somewhere) and dissolve it in the quench water.
Detailed information is given in the two-part article by Oscar L. Gaddy, The Color Case-hardening of Firearms  Winter 1996 and Spring 1997, The Double Gun Journal
I have these articles scanned in pdf form, can email to anyone who wants one but damnifino how to post them on this site. 

[twhrider2]

JC I would love to have the articles by Gaddy, as I plan to try some color hardening this winter. Still gathering info and equipment.
                                                                                                                       Thanks, Ken