How to make a simple folding knife

[LRB]

These penny knives are relatively easy to make, with the exception of the blade slot in the grip. I designed and made a simple jig to hand saw the slot in mine, but most of the originals I've seen are not all that neatly sawed. Some are pretty crude with the slots being off center. They were pretty much considered cheap throw aways. These were originally made by hand, but in a fast production mode, with the workers being paid by the piece, and not on a daily wage.

 

[loki04]

Hence the name 'Penny Knife'?

 

[Vaino]

That "antler knife" sure is beautiful in it's simplicity and unique shape. Have a question....did you anneal the entire file or just the tang? Might want to attempt something like that....Fred

 

[LRB]

I did a simple anneal on the whole file. Heated bright red and just let it air cool. Just doing that will allow you to drill or file it. If you use a cobalt drill bit anyhow. Nicholson files are a hypereutectoid steel, meaning they contain more carbon than the .85% that iron will absorb. The remaining carbon is evenly dispersed as free carbides. If given a standard anneal all the carbon will form layers between the iron, and when you drill, will resist. By heating red hot once and air cooling, you are doing an inbetween anneal, to a full spheroid anneal, which is what is really best. Basicly, if you do a standard anneal, it will be no better than a quick anneal in the case of hypereutectoid steel. Without a heat treat oven, you cannot do the correct anneal anyway. When I made that one, I did not have an oven, but it performs superbly with the quick anneal, and subsequent proper heat treat.

 

[LRB]

I would add to the above, that if you will bring the heat up to a dull red in very dim light, without going non-magnetic, and air cool, about three times, it will be a better anneal. I did not know this when I made that stag folder, but between 900° and around 1350°, the carbon will form tiny spheres instead of layers, or plates, and when air cooled or quenched they will be locked into that condition. These carbon spheres allow cutting tools to pass through much easier than having to go through a series of carbon plates as you would have with a standard anneal. The only negative to this is very minor in that the carbon spheres take a little more time to go back into solution when you do the hardening heat, requireing a couple more minutes in soak time before quench.

 

[paulvallandigham]

Wick: years ago, now, I bought some of those 'Laminated" steel blades to make patch knives. I could not drill the tangs with an ordinary drill bit. I went to the hardware store, and consulted the guy in charge of the Commercial division- who supplied tools and parts to Contractors, and Skilled trades people. He sold me a couple of bits- a replacement bit for the one I burned up the night before trying, a new High Carbon Steel bit, and a bit with an edge made of carbide, which was very expensive. On my way home from work that evening, I remembered watching a Wheelwright putting a 1/4" thick Tire onto a wooden wagon wheel, during an open house at the Lincoln Log Cabin home, South of Charleston, Il. a year before. He heated the steel tire up to red hot and then punched out the 1/4" diameter holes for his rivets using a hoadie punch on his anvil. One blow on one side, turn the strap over, with the help of an assistant, and a second whack with his heavy hammer on the other side, and the plug of steel popped out of the strap.

I decided to try heating the tang up to red hot with my propane torch and see if it would not let my drill cut through then. It works. The drill cut through that tough tang like I was drilling soft pine. Huge chips, that are long and curly, like you would get drilling soft woods. The drill went through the tang so fast I almost lost my balance.

The best part was that the jaws of my bench vise acted as a HEAT SINK, protecting the polished blade from even getting WARM, much less hot, when the tang above the jaws, was RED HOT.

I did not bother to quench that tang after drilling the hole for my cross pin. There was no purpose to doing so.

I do appreciate the information you gave about a salt water quench. I have a former client who learned to use Molten SALT to heat treat, and temper knife blades- this passed down to another friend by his grandfather, who was an old knifemaker. I have NO knowledge of this technique, and have not found any information about it. If you know about it, let me know, Please.

 

[LRB]

Salt baths are now common, and the best heat treat there is, in general, for most steels. Pure salt melts at 1474°, giving the perfect temp for carbon steels to solutionize their carbon. That is also a good way to eliminate guess work for quench temp. There are many smiths who still mistakenly believe steel needs to be quenched at non-magnetic, which is 1414°. That is not enough heat to bring any steel to a full solution condition, but at the point pure salt melts is near perfect. There are different salts used for different temps, and most can be controled for various ranges of heat. Steels that require soak times, can be soaked for shorter periods than if in an oven, because of the heat transfer being much faster in a liquid. There is also no decarb in using salts, because there is no oxygen contact. For some types of heat treating, the steel can go from one salt pot into another, for the quench and temper. The only drawback is the maintenance, and corrosive nature of the salts in the area of use, and for most heat treating, the steel still needs to be oil quenched.

 

[paulvallandigham]

Thank you for the information. Know of any written source of information on salt choice vs. type of steel that I could use as a reference?

 

[LRB]

I checked a supply site, and it offers two heat ranges but does not say exactly what the salts are. They offer high temp, 1300° to 1650°. that would cover all the common carbon steels for the austenitizing heats, but would not austenitize the stainless grades, or the air cooling grades, both requiring higher temps. Then a low temp salt for temper heats from 300° to 1000°. That would cover all the temper ranges for most all steels, whether carbon, high carbon stainless, or air cooling. I would have to think that there are other salts that can be used for HT other than just these two. As I recall, common table salt, in pure form, will not burn, only melt, but perhaps at some point beyond it might vaporize?

 

[paulvallandigham]

I was concerned about using table salt( with iodine, usually added to it) vs. using Sea Salt, or some other "pure" salt- Sodium Chloride( NaCl). I know there are other kinds of salts of all kinds of elements. I don't know the vapor point of salt, but it might be interesting to know. I need to get in touch with one of the blacksmiths I know, and chase down more details on what this mutual acquaintance is using as "salt". I do recall he told me that cooled down, all he had in steel box was a block of salt, which was too heavy to lift out in one piece!

Thanks for the Help, Wick. :hatsoff:

 

[44-henry]

Wick, thanks for the info. I've cobbled together a lot of knives over the years but I never realized that bit of trivia concerning annealing files. I generally have a fair number of students who make knives out of old files in one of my manufacturing classes and our standard treatment is to wrap them in heat treat foil, bring them up to critical temperature range in the furnace, shut it down and let them cool inside overnight. This does work, but every now and than we get ones that are still to hard to work easily and they are terrible on milling cutters if we try to remove stock that way. I'll definitely pass this info down the line. Thanks again.