cleaning up springs

[Davethepainter]

Hi all.  A beginner's question. I polished my springs to get a nice finish, but of course, after I finish forming them, they have a coating of oxide. How do people clean the inside bit, which can't easily be reached? Or does the case hardening take care of that?

[JPK]

Case hardening isn’t generally done to springs.

[rich pierce]

Hi all.  A beginner's question. I polished my springs to get a nice finish, but of course, after I finish forming them, they have a coating of oxide. How do people clean the inside bit, which can't easily be reached? Or does the case hardening take care of that?

Most of us just suffer our way through these things. We can polish a part, harden and temper it, and have to start all over again with the polishing. There are some anti-scale compounds out there and there are furnaces that can reduce oxidation. But most of us just polish twice. In the sharp V bend, I use a file that has a knife edge profile as backing for abrasive paper or cloth.

[Davethepainter]

thanks, btw, I mis-spoke when I said case hardening, I meant the heat treatment for springs.

[Bob Roller]

My springs are fully formed and opened to the configuration needed and after cooling they were polished and inspected and then heated to an orange color and dropped into an old motor oil drained from a diesel bus engine 50 years ago.After cooling it is removed with  magnet,washed with lacquer thinner,polished and then drawn to a dark blue and allowed to cool at ambient air temperature in the shop.
Using a consistent quality spring steel is a must.I have used 1075 for over 50 years and so far no reported problems and I have locks all over the world.
Bob Roller

[kutter]

You can remove the Heat Scale from the hardening process by letting the part soak in a weak soln of
Muriatic Acid. (which is a less than pure form of hydrochloric acid and can be bought OTC at places like Home Depot)

I use it often for that reason in removing heat scale from parts that have been welded or hard soldered, or have been annealed by just heating them in the open air and they have the heat scale on them.

A couple tablespoons to a pint of water,,or even a quart of water will work.
It's slow but that's OK. It won't pit the bare steel that way but will leave it with a dull gray color, much like the French Grey color finish some parts are finished up with after engraving (hint).

The heat scale will turn a jet black color on the surface and much or if will fall off on it's own. Tha which remains will be very thin and can be wiped free of the surface with just your finger tips.
No, the soln won't burn your skin. It will sting it you have an open cut on t though and it gets in there.

Rinse with some dish soap and water, then clean water.
Remember that when handling the hardened Spring that they are BRITTLE hard and can be easily broken or snapped if you
compress it or bend it.
But at this point you can easily polish the surfaces once again and START with 600 or higher grit to bring back the shine it orig had.
Saves lots of work.

If you are drawing the spring back in a molten lead bath and want to keep the lead from sticking to the spring, cover the spring with a coating of soot from a candle ,,(I use the acet flame on the OA torch).
The soot coating keeps the lead from sticking
k

[bluenoser]

I have read that a layer of soot will also eliminate or significantly reduce heat scale when hardening.  Haven't tried it, but think I might in place of anti scale compound on the next heat treat job.
Anyone else have any experience with it?

[Habu]

Soot shouldn't be too hard to test. 

As a kid I was taught to use a mix of 9 parts boric acid and 1 part iron oxide (my job was to scrape the rust off the scrap pile, and shake the bottle once it was mixed).  Heat the metal up to ~350-400 degrees F and sprinkle the powder on from a salt shaker.  It turns glass-like, and when you quench almost all of it breaks off.  This does work, I saw several well-known bladesmiths use similar mixes.

On more than one occasion though I saw Old Man K use welding flux (50-50 mix of borax and powdered brown glass).  I think this works a bit better on springs, but it is harder to clean off. 

These days, for lock springs etc I just paint the spring with White-Out.  It works as well as the stuff above or the commercial mixes, and I'm such a lousy typist I have a lifetime supply.  When it dries up in the bottle, thin it with alcohol.

[davec2]

https://www.brownells.com/tools-cleaning/paint-metal-prep/metal-bluing/non-scaling-compound/

Works great.....

[kutter]

Boric Acid does work nicely. But don't go cheap and use the ant &roach killer stuff from the home improvement store that is 90%+ Boric Acid.
What ever that last % is in that stuff, some sort of vegetable matter I suspect, will puff up like a bread dough when you spread it onto the part and heat it up red hot. Those areas that show this will not come clean of the substance when you quench the spring(part) like the real Boric Acid 'shell' will.
The real Boric Acid will crack and break away from the part and leave it  nice and clean. No scale on it at all. That scummy burnt bread like stuff will still be clinging to the parts and have to be polished off and even then it leaves an etched pattern around the perimeter in the steel of where it was on the part.

When I was first shown to use Boric Acid back in the early 70's it was for making engraving punches and stamps and HT them to avoid scale on them.
The Boric Acid was bought off the shelf in a regular drug store in small cardboard boxes w/a pry off metal top.
It's used for a lot of medicinal stuff like eye wash in weak soln, etc.
Thats the pure stuff that works very nicely.

Take the steel part/spring/punch tied to a wire,, and roll it in the boric acid powder/crystals which you have mixed with common alcohol. You want a paste of the stuff so it can stick to the part, the alcohol quickly start to evaporate and then add more to it to build it up.
Acetone works well too.
Build the surface up with a layer of the boric acid to form a 'shell' around the part to seal it inside of the Boric acid.

Once the shell is built up sufficiently, light off the alcohol from the Boric acid with a lighter or match. This will leave the shell hard but very brittle.
Handle it with care.
From here the encased part can be heated with torch or in an oven to the required temp.
Then carefully lowered into the quench.

The Boric Acid shell will crack and spatter and release itself from around the part completely.
Pull the part back out on the wire and it will be a very hard but clean steel part ready for drawing back or if you want to,, a little extra polish before hand.

Save the Home Depot Ant& Roach Killer Boric Acid stuff for the insects.. I learned that the hard way so you don't have to.