The Blue Screw

[Zonie]

I'll get to the blue screw in a minute but first I would like to talk about tang screws.

Recently a post asked about the shape of the head for a tang screw. You know, "Are they usually flat head screws or some other shape?"

The answer from most of the folks who have handled a lot of original rifles is that they are countersunk screws with a slightly rounded head.
Not a full "round head" screw, more of an "oval domed" or "button head" shape.

Folks who choose to buy a slotted flat head screw have two choices. They can either leave it as it is or they can modify it a bit.

I recently bought some #8-32 slotted flat head screws at my local hardware store. As they come, they have a head diameter of .310.
If I choose to leave them as they come and use them with a straight tanged breech plug I can see a problem ahead.
Many straight breech plug tangs are only about 3/8 of an inch wide. That is .375 of an inch.
If I leave the head on my new flat head screws alone, and I countersink the hole for the tang screw for a .310 diameter head, that only leaves about .033 of flat on either side of the head.
With this small amount of material, the slightest error in locating the hole right in the middle of the tang will make a very noticable "error" causing the viewer of the gun to instantly notice that one side of the head of the screw and the side of the tang and the other are very different.

Leaving only 1/32 of an inch of tang material (or less) on each side of the screw head also greatly weakens the tang so it can easily become damaged.

If the "land" is wider than 1/32 of an inch the mis-location will not be as obvious and the tang will be much stronger.

The solution? Kill two birds with one stone by modifying the heads shape into a "oval domed" screw.
This can easily be done with a portable electric drill and a small flat file.

First, chuck the screw lightly in the drill and lay it on a table with the chuck pointing to the right.
Now, with the drill held in your left hand and running, place the file on the flat face of the upper side of the screw head and push the file forward working mainly on the side nearest to the conical surface.
By removing material from this area the shape of the screw will become "domed".
Not only will this create a more correct looking screw but it also reduces the outside diameter of the head.

Because some of the material is removed, it is a good idea to use a hack saw to increase the depth of the screwdriver slot a bit.
Don't get carried away and go too far. Just a little increase is all that is needed.
For the perfectionists, cleaning up the bottom of the slot with a knife shaped file should be considered.

After reforming the head you might want to sand it to remove any file marks. A good wet/dry silicone carbide (black) sandpaper will work nicely.
I go one step further and polish the head to a mirror bright finish with my "stainless" polishing compound applied to my buffing wheel.

After doing this to one of my screws, the finished head diameter is now about .265.
A .265 diameter head will leave almost 1/16 of an inch of flat on either side of the head when it is installed into the tang. With this much tang surface showing on either side of the screw head, a little error in the centrality of the screw will not be noticable to the bare eye and the tang will be much stronger.

Now, with that out of the way, I'll move towards the blue screw.

Some of us really hate to see a screw head "buggered up". Even the smallest ding or nick in the slot stands out like a sore thumb.
For this reason, many of us harden the screw heads surface. A hard surface on a screw head is hard to nick even if the wrong screw driver is used.

Because the steel most commercial screws from the hardware store are made out of low carbon steel, they won't harden with thermal heat treatments without a little help.
The only way to harden these screws is by using a carburizing compound like Kasenit.
This stuff puts carbon into the steels surface raising it into a high carbon steel that can be hardened.
Although this high carbon layer is very thin, after it is hardened it will serve nicely to protect the screw head and slot from nicks and burrs.
Kasenit by the way doesn't give off any poisonous gases and it is very easy to use.

You will need a small bowl of water, some Kasenit, some plyers and a propane torch.

Hold the screw by the shank and heat the head to a bright red hot color. Plunge it into the dry Kasenit and hold it there to form a large blob that is stuck to the screw head.

Now, reheat the blob to a bright red/orange color and keep it this color for at least a minute. Five or ten works better but it may require re dipping to replace the material that has been burned off.
When your tired of watching the blob glow, drop the screw directly from it's red hot condition directly into the water.
When it hits the water, the liquid Kasenit will "Pop" and break off of the metal surface.
This will also harden the newly created high carbon steel. :grin:
Wipe or rub off any Kasenit that sticks to the surface. You may want to re polish the surface but don't use sandpaper. The hard coating is very thin and you don't want to remove much if any of it.

Now to the Blue Screw:

I think a heat blued steel is a beautiful thing indeed. It adds a touch of "class" to any gun.
It also "tempers" the newly hardened steel to remove some of its brittle condition leaving is hard but strong.
You will need your propane torch, some pliers, a small bowl of motor oil (or transmission fluid) and the screw.

Holding your screw in the pliers and adjusting your propane torch down to its lowest flame, gently direct the flame at the screws shank under the head (not at the head). You want to heat it very slowly.

As it gets hotter, the color of the head will first turn a light straw color, then a darker yellow, then brown, then purple and then blue.

When the last of the purple color turns blue, instantly drop the screw into the bowl of oil and let it cool down.

If you waited too long, the blue will start to turn a gray color. If this happens, all is not lost.
Simply re sand and re polish it to remove the gray and try again.
Properly done, the screw head will be a rich dark beautiful blue. The kind that the old Colts were famous for.

Yes, one can also use a pot of molten lead to color steel blue but why fart around with a pot of hot lead when this simple propane torch method works so well?

Oh, for you folks who just want to color your screw heads blue, you don't have to go thru the carburizing process if you don't mind having a soft steel part. Just go back to the last paragraph where I described the heating and oil quenching and your finished screw will be a buautiful dark blue color.

This "heat bluing" can be done to any steel part. In fact, rightly or wrongly I used this method for bluing the polished cock on the flintlock that is going on my next rifle.
I think the blue cock against the browned lockplate is quite attractive.

Have fun.

 

[faw3]

Seeing the blue screw and by you I thought he's gone out of his mind. Safe Again , thanks "Z" Fred :hatsoff:

 

[mazo kid]

Zonie, thanks for the "walk-through" about screws. One thing I do for "buggered" screws is drill a hole through a piece of steel that will allow the screw threads to pass through. Put the steel with the screw in your vise and use a light hammer and tap the edges of the slot that are raised. This will sometimes dress the slot up nicely enough to reuse; you may also have to file the slot even as it can make the slot thinner in places. I also use your oval head screw forming technique for making wood screws as the oval straight slotted screws are getting hard to find, especially in several different sizes. I sometimes wind a piece of wire around the screw when fire bluing just to make holding it a bit easier. Emery

 

[pichou]

I don't want to sound contradictory, cause you got more experience than me for sure, but...

I have looked at and taken apart a bunch of Brit guns, and they almost always have wood screws that are lopsided, slots off center, etc. On the surface though they are perfectly flush with the metal. I think they were filed to profile in the final finish. If you take one out you will know. When you put it back, you have to keep turning until it lies flush again. If you don't it will stick up with a sharp edge. You also can't switch the screws around.
:v

 

[LRB]

Like you said. Brit guns. What time period on these?

 

[pichou]

Mostly 1800-1850. Birmingham guns.

:surrender:

Brass is low oval or flat. Mostly flat. Steel is flat. Lock screws are a whole different topic of course. And the screws are usually engraved.

So what about American guns? Low oval on brass, but what on iron/steel mounts?

I would love to get my paws on some early American guns but it hasn't happened yet.

I wonder what the story is on French and German(ic) guns?

 

[LRB]

18th c. American, early 19th c. American, low oval iron screws. Whether brass, or iron mounts. Of course, it is risky to say 100%, but relatively safe. French, and German about the same, as far as I know. Stophel is pretty sharp on those, and American guns too for that matter. I just build them as best I can, and as historically accurate as I know. At least as far as what you see. :wink: :grin:

 

[paulvallandigham]

If I recall something I read once, correctly?, The European system of apprenticeship required new apprentices to spend years perfecting their technique in using files. Screws were therefore made by hand filing them to shape, long after other methods were being employed in some countries. I know the screw plates were a common item fairly early in the colonies, and were used to thread rod stock to make screws, rather than file them to shape. The Master/apprentice system did not fair well in the colonies, because you could not keep an indentured apprentice for the many years that occurred in Europe. Apprentices could easily run away, to the west, and open their own businesses where they could make a living wage without all the abuse that many masters felt was their right to dish out. ( Do unto others as was done unto me!) We need to remember that even Ben Franklin ran away from an abusive relative to start his own printing business in Philadephia.

 

[pichou]

I thought Ben ran away cause he couldn't stand the smell of rendering tallow.

The wood screws I see are lathe cut with hand cut slots. I haven't seen anything that looked like hand cut machine screw threads. Screw plates were pretty standard.

I have seen non gun stuff like brass candlesticks that had hand filed threads, but that is to clean up the casting, not from scratch.

 

[Tinker2]

Thanks Zonie

Very well done, you are a good asset.


Tinker2

 

[flashpanner]

I am with you on this one. I case hardened all of my screw heads. I then polished them afterwards. They stay nice and pretty and do not distort when tightening them.

 

[paulvallandigham]

The first hand made screw I ever saw came from a late 18th century rifle a friend of the family was trying to restore. I was only a kid of 11-12, and it inspired me to become interested in old guns. I did not know it was possible to make a screw from a piece of iron, using a file, but there it was.

I believe he thought it was American, only because he thought it was made in Pennsylvania, by german smiths. The Barrel was about 3 inches across the flats, however, and made from a butter soft iron I have never seen since.

I believe now it was a Jaeger rifle, possibly restocked. The Action was missing, and I did not know enough then about the difference between flintlocks and Percussion locks to tell whether it had been converted to percussion sometime in its life. I remember the gun weighed more than 30 lbs, and had a very small bore that was out of round at the muzzle. I believe the screw he showed us came from the trigger guard, which looked much more like a Jaeger guard, than the later pieces made here in America. Everything was rusted, unfortunately, as the piece had been badly neglected before he got it. It was years before I had any ideas about the value of such pieces, and the owner died while I was in College. I have no idea what happened to that rifle. The next time I saw a hand made screw was in a museum display.

 

[ricklandes]

Paul...is that a typo..."3 inches across the flats" ?? Sounds like some early rendition of a punt gun if that is a correct (guesstimate) measurement.

 

[paulvallandigham]

The gun stood only chest high on me at age 11, so the barrel was about 36 inches long. You figure out how much metal would be required to make the gun weigh over 30 lbs.

No, it was no typo. That is what made the gun so unusual, and why I still remember it. It was too heavy for me to pick the gun up and mount it to my shoulder then. I suppose I could do so today, but how long I could hold it, and then fire it accurately would still be a question. We assumed it was used as a squirrel rifle, always used with a rest. I just don't know who they got to carry it into the woods each time! :rotf:

 

[Allan Gray]

Good stuff Zonie!

May I add; I was taught to polish the screw head to a mirror finish before the heating/oil quench.
Have you found that this is not needed?

Also, I've seen some pretty nice looking colors between the blue and grey phase.
If you're timing is right you can catch them, but you've got to be fast!

Thanks!

 

[Zonie]

Mr. Gray:
I first file form the head, dress up the slot, then sand it, then polish it, then carburize it and quench it.
Then I repolish it, fire blue and oil quench it in that order.

Although these metal colors are very thin, with the proper oil protection they can last for years.

My 1906 Luger for instance still has the original light yellow color on its extractor and it was made 102 years ago. (It was also well kept so it is still 98% condition.)

 

[barebackjack]

Whats the molten lead method you mentioned zonie? Hows that work?

 

[ricklandes]

Now that the brain is (more) fully functioning...I re-read the 3" across the flats...I was thinking of each flat of the octogon as being 3" (which would make a 6" wide barrel!!! :shocked2: )rather than the side to side measure of 3"...or a barrel with 1 1/2 flats...


I had seen one of similar size at a local rendevous, .50 cal target for long range bench shoots...about the same weight as a 1964 VW bug!

 

[paulvallandigham]

Isn't it funny how we always remember the odd ones we run across in life, out of all the hundreds or thousands of guns we have seen. I can remember hardly being able to lift that rifle I saw up of the floor, because it weighed so much. I was, of course, more concerned about dropping it, or doing anything with it that might damage this obvious antique gun, but WOW! Was it heavy for a little kid! Several years later Gun Digest published a story by Hal Hartley, and noted Gunstocker, telling about how he found, and then restored a famous MLer that his grandfather used to win shooting matches when he was a boy. That is the next time I thought of that monsterous gun, and wondered what happened to it after the owner died.

 

[Zonie]

Whats the molten lead method you mentioned zonie? Hows that work?

Pure lead melts at 618 degrees F, and most folks who cast it into bullets/balls increase this temperature to about 700 degrees F.

To check on the leads temperature many use a high temperature thermometer that easily determines it.

According to one of my metal working books, the "blue" color on carbon steel occurs at about 570 degrees F. although temperatures up into the mid 600's will not push the color into the gray areas so, if you have a setup for casting bullets/balls you can heat the lead up and measure its temperature to see if it is in the 630-650 degree range and then insert your part into it.

Some say that holding the part in the melted lead will increase the thickness of the bluing making it wear better. I don't know if this is true or not.