HArdening screw heads?

[Bigmon]

Another sort of finishing up question for you all?  Between finish coats on this rifle I am finishing up my metal work.
I have read on here that some of you harden your screw and bolt heads?  This seems like a good idea if not too complicated, as usually my screw and bolt heads get a little messed up during the build.
Can this be done by just heating and quenching, or do I need a hardening product?

[L. Akers]

Unless your screws are made from high carbon steel ( I very much doubt they are) you will have to use a hardening product.

[E.vonAschwege]

You can buy a carburizing compound for hardening screw heads and other small parts.  Kasenit used to be great, but is no longer made.  A product called "Cherry Red" works very well too.  Use a torch to heat up the screw head to a dull red, dip it in the powder which will stick to the part, then reheat and hold for several minutes.  Quench in warm water and you'll have a nicely hardened surface.  It's not like deep case hardening/carburizing, but it'll keep the head from getting dinged up as much with a turnscrew. 
-Eric

[Hungry Horse]

This sounds like more busy work at the sanitarium, to me. After assembly how often do you disassemble your guns? I could maybe see some wear, and dings, on the lock bolts, but everything else pretty much stays as assembled, at least mine do. Besides hardening can make bolts, and screws brittle. I’d rather have a dinged screw, or bolt, than a sheared off one.

  Hungry Horse

[Eric Kettenburg]

I like to caseharden screws but at the same time I would very much heed the warning about shearing.  I found with smaller screws (#4 or #6 size) that kasenit or an old-style crucible case can very easily through-harden them to the point that they are indeed brittle and will shear quite easily if you are one of those Hercules screw-turning types.  I don't think it's that important with wood screws throughout the rifle (as noted above, there's really no reason to be regularly turning them anyway) but historically lock part screws would certainly be casehardened and also - most likely - the lock bolts.  So harden away, especially if they're a soft non-carbon steel, but be sure to draw them back a bit just to avoid future headaches.

[45-110]

i harden every screw on my guns after a thorough polish, kasenit for the mild steel ones and heat treating for the tool steel  screws.
nothing says "cheap" more than buggered screws.
kw

[smart dog]

Hi,
It is a very smart and good idea to harden your lock and tang bolt heads as well as the top jaw screw and tumbler screw.  I also do the screws in the butt plate.  Hardened screws not only resist wear but also rust.  However, after hardening with Cherry Red or Kasenit, temper them to blue.  On an original fowler I own, those temper colors still show a little on the tumbler screw.  I leave the blue color because it is very attractive while it lasts.  The photos below can give you an idea how nice blued screw heads look in various contexts. The color eventually fades but the wear and rust resistance remains. 

dave

[Mikeh]

What is the best way to tell the screws apart, tool steel from mild steel? Thanks!  Mikeh

[Lzymtlsmth]

i harden every screw on my guns after a thorough polish, kasenit for the mild steel ones and heat treating for the tool steel  screws.
nothing says "cheap" more than buggered screws.
kw

Never have seen tool steel screws except for cap head screws or hardened bolts on machinery. The common screws at hardware or you buy at ml suppliers are mild steel I would guess. Stainless another category altogether.
I heat blue my screws till they turn purplish blue then dip in motor oil or beeswax use before final
assembly.seem to hold up pretty well.

[David R. Pennington]

Probably the surest method to determine if the screw is carbon steel or mild steel is to try hardening without any compound. Heated to bright red and quenched in oil should give a hardened surface if it is carbon steel. If it hardens this way you will then need to heat it again in controlled manner to soften (temper) it some or it will be brittle and likely to break.
If this has no affect then you have mild steel and will need to use the compound to produce a case hardened surface.
Once you learn what to look for you can get a pretty good idea of what material you have by watching the sparks from high speed grinder but this is not a good idea for screws unless you have spares.

[Dave Marsh]

I have been hardening my screw heads by heating them to red and then dunking them in Cherry Red and then heating them to red again and dunking them in warm water as Eric described.  I guess I am missing the tempering process.  Is that heating them up again to blue and not red and then quenching them in water again??  Thanks.

Dave

[jerrywh]

 Most of the time I case harden the whole lock screws included and then draw all of the parts back. I draw the screws to 600°F.  However if I only have a couple of screws to do I use potassium Ferro Cyanide.  Potassium Ferro Cyanide was the main ingredient or Kasinite. I have been using this for over 50 years.  You can by it on Ebay in the form of  Potassium Ferro Cyanide trihydrate. It is used exactly the same as kasenite was.  Before kasenite was invented this is what was used by blacksmiths.
https://www.ebay.com/itm/Potassium-Ferrocyanide-Trihydrate-500-Grams/183719831149?hash=item2ac68e266d:g:BUwAAOSwXIFcgYei

[Eric Kettenburg]

BTW, for anyone interested, I recently got a pretty big load of various unplated wood screws from Blacksmith bolt/rivet, which is where I believe a lot of us here get them.  I don't know what they're made of but they are SOFT and brittle at the same time.  Probably junk Chinese steel.  I've already sheared off a couple in maple which I haven't done in probably 20 years, and I'm not going overboard with the tightening.  These will need casehardening for sure as I'm buggering the heads just looking at them! 

[Bigmon]

Thanks to all.  Quite an education.

[jerrywh]

 In the old days potassium ferro cyanide was called prussiate of potash. It is safe to use as long as you don't eat it or put acid in it. If you look up the safety data sheet on Kasenite you will see that it is the same thing.  Cherry red is nothing but potassium nitrate and chromium oxide. It hardens iron by infusing nitrogen into the iron.. Chicken manuer will do the same thing if you use it in a pack hardening process.

[D. Taylor Sapergia]

Many many years ago, in the last century, I was given a steel tub of a product called "Hard 'n Tuff"  It came from a saw-filer at a mill and I've used it successfully since then for case hardening lots of things.  It is green in colour and is a powder.  The instructions on the can say to heat the steel red, dip the part into the pwder, heat to red again and hold at that temp for several minutes.  This produces a glass hard skin on soft steel screws, such as tang and lock attachment screws.  I also do the wood screws that hold the buttplate on.  I often engrave screw heads, and I cannot bear to see these buggered by the ham-fisted clients who bring back a rifle for service...they usually don't even notice the damage.  Hardening the screw's heads makes all the difference.  After hardening, I use a soft wire wheel at 2500 rpm to burnish the screws, which further polishes them and removes the scale left during the process of hardening.  Here's an example, from the pistol I recently posted...




As long as the screws are free machining leaded screw stock, drawing the temper has not been necessary.  I caution you though about flint cock screws.  I would definitely draw the temper to at least purple - blue is better - because many are tool steel.

[Craig Wilcox]

Well, Jerry - you taught me something AND gave me a use for some of my son's chicken s**t!  Something had gotten after his hens - and killed the rooster - so he berthed them for a time in the garage - where I live in one bay!
Took some getting used to the chickens waking up in the morning, but I refused to get used to them doing their business on the cast iron top of my table and bandsaws!  Their excrement is slightly acid, and can erode the polished CI surface.
So, he has a new rooster, and has re-secured the coop - and now I have a use for the manure left behind - many thanks for the idea!
For quite some time, I have merely heated the screws to about 600-700 deg, turning them a dark blue.  Kind of coloring them - they are not much harder that way, but they do look nice.

[flinchrocket]

I use Cherry Red and it is my understanding that you don't need to temper. It is only a thin layer of hard coating,not all the way through.

[Bob Roller]

I use Cherry Red and it is my understanding that you don't need to temper. It is only a thin layer of hard coating,not all the way through.

Chet Shoults once told me that case hardening was so thin there was only ONE side to it.
That being said,unless the gun or lock is being dismantled after every shooting event,
is there any real need for hardened screw heads? I have NEVER hardened lock screws
even those I made from drill rod. I buy screw material the diameter needed for the screw heads
which in my locks is 5/32" or .157. I use 12L14 and bought a very long time supply for very
little money years ago and am still using it.Same for hammer screws.3/8" usually.
Learn to file a screw driver to fit the screw slots and that should work well with or without
a hardened screw.

Bob Roller

[Eric Kettenburg]

One reason I still believe it to be a good idea to harden and temper internal lock screws is because most new locks are not made in the same manner as old locks.  For example, many old locks made use of not merely a forward bridle screw but also a peg which fit a hole in the lockplate.  When the tumbler whacks against the internal bridle stop, the peg was taking the brunt of the force and the forward screw was simply reinforcement, holding it in place.  Now most locks do not feature such a peg, and so that forward bridge screw is absorbing all of the force of tumbler (or the force of the tumbler not absorbed by the frizzen).  Better locks - mostly English but I've seen some continental as well - also used a peg or leg at the bottom of the bridle to further lock the bridle immovably into place.  Then you have screws like a sear screw or a frizzen screw which are providing a bearing surface to components which are themselves hardened and tempered to various extent.  I think it best for longevity and wear resistance that the bearing surface (the shaft of the screw) be possessive of at least a comparable wear resistance to the part rotating around it.

[flinchrocket]

When you make a gun for someone you have no idea what kind of abuse it will encounter. Some people don't know how to use a screwdriver or how tight is to much?

[rick/pa]

^^^  What Flinchrocket said.  Some guys go by the axiom, "Tight as she'll go, then 1/4 turn more."

[Daryl]

Turn it until it strips, then back off 1/4 turn.

[Lzymtlsmth]

BTW, for anyone interested, I recently got a pretty big load of various unplated wood screws from Blacksmith bolt/rivet, which is where I believe a lot of us here get them.  I don't know what they're made of but they are SOFT and brittle at the same time.  Probably junk Chinese steel.  I've already sheared off a couple in maple which I haven't done in probably 20 years, and I'm not going overboard with the tightening.  These will need casehardening for sure as I'm buggering the heads just looking at them!

What they need is sent back for a refund imho. Using inferior product no deal in my book.
“ once the sweetness of a cheap price is gone, the bitterness of poor quality remains.”
Kent

[Bob Roller]

IF the tumbler strikes the bridle during the shot cycle the a wee bit of filing
should solve that problem.If it's a hard strike a hardened steel screw might break
and as far as the rotation of the sear is concerned that should never be a problem.

Bob Roller