Fire-bluing screw heads

[Larry Pletcher]

I fire-blued lock retaining screws and a top jar screw last night.  I got the first one pretty well, but must have over heated the second one.  I buffed it out and tried again.  Apparently the change from straw to blue goes pretty fast.  Maybe I need to move the heat farther away.  Any suggestions to help out?  

Another question:  Do you do anything to protect the bluing, like a coating of wax

Thanks.
Regards,
Pletch

[Long John]

Fire bluing should be done slowly.  If you heat the object too quickly you are likely to over-shoot the deep blue and end up with a frosty gray-blue.  Re-polish and try again.

I usually quench my parts in bear grease once I have gotten to the color I want.

Fire bluing will wear off and age with time.  It is one of the least durable finishes in my limited experience.

Best Regards,

JMC

[Acer Saccharum]

Asan alternative, Pletch, you can heat the parts in a tuna can in a deep charcoal fire for about a half an hour at a red heat. Dump out in clean warm water. Can't tell you what color exactly you will get, tho'.

Pack the parts in crushed charcoal in the can, drop the cut off tin lid to keep out oxygen. Cook for 1/2 hr at 1500 deg.

This will case harden the parts, and also provide a skin of HARD surface steel, great for screws and screw slots!

Tom

[40Haines]

Should be one of the easiest things we do.

I'll be darned if I  can get the deep rich blue CONSISTENTLY that others do.

I have even turned the lights out to better see the straw color.

Maybe heating slowly is the trick.

Jim seems to have no problem with it.

[Don Getz]

I will hold the shank of the screw with a needle nose pliers and heat the shank, using a propane torch.   I move the screw
in and out of the flame and at a certain point you will see the color start to rise up thru the head.   When it starts to do
this, take it out of the flame and watch for the color that you want, when it hits that brilliant blue, quench it quickly......Don

[Acer Saccharum]

You need good light to watch the colors rise. Once you see straw , then you have a few degrees til it turns blue, so at this point, back off the torch, and tease the heat until you reach your desired color. Teasing the heat allows the colors to even out from thick to thin sections. Quench in oil. I like boiled linseed, as it leaves a protective film.

By teasing I mean pull the torch back, and play on and off the part, giving the heat only to the sections that have least color. This allows the colors to change slowly, which gives you time to react when you reach the color you like.

Heat small parts on a steel or aluminum plate, playing the heat from under the plate.

tom

[Dphariss]

I fire-blued lock retaining screws and a top jar screw last night.  I got the first one pretty well, but must have over heated the second one.  I buffed it out and tried again.  Apparently the change from straw to blue goes pretty fast.  Maybe I need to move the heat farther away.  Any suggestions to help out? 

Another question:  Do you do anything to protect the bluing, like a coating of wax

Thanks.
Regards,
Pletch

Propane torch, heat the shank of the screw and let the heat flow to the head. As the color comes right quench.
If it needs blue on each end heat the middle.
It takes practice.
If you want to get really high tech make a small tank, I used a piece of conduit with the zinc burnt or pickled off, welded ends on it and holes for heavy wire to hang it from for longer pieces like mainsprings and a stainless soup ladle for smaller parts, fill with potassium nitrate and heat till it melts, 700 degrees or so. Immerse the part to be blued. As the coating melts off the color will start to come. Its often necessary to immerse the big end first since it heats slower. This is the best way to do larger parts.
According to the Madis book Winchester blued barrels with PN with some manganese dioxide in it. When the proper color is reached to part is removed and when clean and cool it is coated with oil and the oil baked off.
I have tried this and it does make a darker blue that is a little more durable. But the color is not the fire blue anymore. Heavier oil makes darker color. It can be used to blue parts that need to match the typical blue found on modern guns to "fix" a screw etc that needs color to match.
The Manganese makes the molten PN darker and its harder to judge the color. I tend to use straight PN though my one "tank" still has the oxide in it.
PN should be available on the WWW and Brownells sells it in buckets.
The PN "evaporates" into oxygen so it goes away in use and needs a refill now and then. When using this process it is best to get all the parts to be blued ready and do them in a batch.
Some PN will adhere to the part but it dissolves in water.
I don't know of anything other than the lacquer used to coat color casehardening that will protect the color.

This process is good for tempering springs BTW. Residue washes right off leaving a nice blue, clean spring. I let these air cool and wash the spring later to remove the remaining PN.
I think this process make a *somewhat* more durable coating.

Dan

[northmn]

I will hold the shank of the screw with a needle nose pliers and heat the shank, using a propane torch.   I move the screw
in and out of the flame and at a certain point you will see the color start to rise up thru the head.   When it starts to do
this, take it out of the flame and watch for the color that you want, when it hits that brilliant blue, quench it quickly......Don

I have done many small parts that way including buttplates.  Use motor oil or as Acer suggested, Linseed oil.  Its pretty durable.  Hardware store screws have a zinc coating that I remove with a wire brush wheel.

DP

[Larry Pletcher]

Thank you for all the advice.  I just finished the cock screw; turned out well.  Since it was so short, I wondered how I'd heat the shank of the screw.  I started it on a ramrod end and played it in the torch flame.  I could see the color come in and went slow when I saw the straw.  When quenched and cool I replaced it.  I guess a fire blued top jar screw and a cock screw are a little out of place on an unpolished lock.  Guess polishing the lock will be the next thing to try.

Thanks again for your thoughts.
Regards,
Pletch

[flintriflesmith]

For fire bluing screws, top jaws, and other small parts I find a candle (or alcohol lamp) and blowpipe better than a propane torch. The heat is plenty but the control much more precise. Jeweler supply places sell them.

Larry, think back to your teaching days. Remember borax bead tests in chem class.

Also instead of holding the part with pliers, which suck away the heat, place it on a block of charcoal. The charcoal heats right up along with the part. A small amount burns off during each use.

Gary

[jerrywh]

 The secret is SLOW.

[Waksupi]

I like using nitre for such projects.  Easier to watch the colors, than using flame. Another way to do it, is a pot of melted lead, and dip the pieces until the color is reached.

[J. Talbert]

I found a while back that I get better control by placing the part on very thin sheet of copper with the edges bent up to make a shallow tray, and then play the flame from a propane torch beneath it.  I can get slow even heat and more consistent color.
For screws that only the head shows, such as the cock retaining screw, I drill a small hole in the copper and let the shaft hang out the bottom.

This method has worked well for me.

Jeff

[B Shipman]

Not to change the subject, but I could never understand the point in softening a screw head. It is pretty. But I'd rather case harden the heads to avoid the slots getting buggered with hard use. Shanks soft to avoid beakage.

[Dphariss]

Not to change the subject, but I could never understand the point in softening a screw head. It is pretty. But I'd rather case harden the heads to avoid the slots getting buggered with hard use. Shanks soft to avoid beakage.

I have had  casehardened screws chip at the edges of the slot. Bluing them just brings the case to a spring temper, still pretty tough and its worked well for me a quite a few screws.

Dan

[jmforge]

Remember that to get most steel blue, you don't need to go much hotter than 500F.  Depending on the steel, you can do it in your kitchen oven in a pinch. A cheapo toaster oven is also supposed to work fairly well.   With that said, since most screws are made out of pretty crappy mild steel these days, perhaps the case hardening suggestion is a good one.

[rick landes]

If I have a series of small items, e.g. screws to do. I like to make a quick holding jig from annealed black wire. The stuff is easy to finger shape and strong enough to lock into a vise, hold its shape and support the part.

Make sure to clean and degrease your parts prior to heating. I use an extra small head on a propane torch for a very slow heat. I give a bit of heat by waving the flame across the part, and then let in cool so the heat can fully sink into the metal. If color is not right, wave the heat past it again. I think many begin by heating the part to the desired color and then removing the heat, however they soon learn the heat continues to sink in and move the color past the desired hue.

I am faster at doing it slow and right the first try versus polishing that grey out and redoing everything. Don't ask me how I know.

I remember one time doing a hammer forged candle stand for a friend and fire bluing it to that nice sapphire color. I was able to find just the right temp to push the color up the material length akin to using a spray bomb on it. I wish it were that easy every time!

[NSBrown]

Rick - I have learned the same lesson. The way I say it is: "The slower I go, the sooner I get done."

[B Shipman]

When's the last time anyone has seen a chipped screw slot as opposed to a buggered and worn one. About one to 10 thousand.

[Acer Saccharum]

When's the last time anyone has seen a chipped screw slot as opposed to a buggered and worn one. About one to 10 thousand.

COme to think of it, Bill, I have seen about nine thousand buggered slots, still have yet to see my first chipped one.

Actually, I have seen some on original shotgouns, where I thought the screws were cased all the way through, and the screwheads were delicate to begin with.

[Long John]

You guys have me convinced!  I just might even take all the screws off the Bucks County squirrel rifle and case-harden them, too! 

Once you have built the set-up for case hardening the actual act of doing it is not such a big deal.  It seems that you could case harden small parts with a back-yard charcoal grill and a bellows.

JMC

[Larry Pletcher]

Gentlemen,
Thank you all for your advice.  Slow does indeed help.  The idea of heating the shank of the screw and watching color was  helpful , as were all the rest.  I hunted up a number of screws, polished and blued them for practice.  The old golfer's saying, "The more I practice the luckier I get."  Also I now have a fairly  plain Lancaster with fire-blued screws that would be more correctly browned, but I learned something new and had to try it.

Thanks again -- the only thing more fun than teaching is learning.

Regards,
Pletch

[Acer Saccharum]

Just to add some options, you can caseharden the screws first, which will make them tough and wear resistant. THEN you can polish them up and fire blue them. Now You must be careful not to exceed the blue, because you are in essence drawing the temper on a carbon steel case. Warning: If you go too high with your temp, you will draw the hardness from the case, voiding much of the benefit of the case.

Acer

[Larry Pletcher]

One additional thing I learned is that a good polishing is called for.  The best job of blue was  when the screws were polished so that it looked like you could see facets in the shine.  If they looked like that before bluing, they had the same faceted look in the blue.

Regards,
Pletch

[Acer Saccharum]

One additional thing I learned is that a good polishing is called for. 
Regards,
Pletch

Yep, Pletch, the higher the polish, the richer and brighter the blue.