Make Your Own "Hallmark" Stamp

By suggestion of my nephew, I decided to make my own hallmark stamp. I think anybody that makes things should have a mark of some sort, to identify them as the maker. I have used a derivation of my initials to mark some items I've made in the past using ink (most items bear no mark); time to try something permanent and carve it from steel, in stamp form! I wanted it to be hard and durable, so I selected a rarely used tool for the job, a hex key socket fit the bill nicely (Tool steel is best, I think). First I needed a pattern, so I printed a honeycomb pattern I found on line, that I then scaled to fit my 1/2" hex key. I then made my mark a number of times to find a pattern that I found suitable, and would use five of the six points available on the key. I then cut it out, applied some super-glue and clamped it tightly in the vise to dry. While it was drying I heated the end of the key to beyond its' magnetic point (transformation temperature), with a propane torch supported inside a sort of furnace made from fiberglass insulation that had the paper stripped from the outside (be very careful doing things like this at home, though the fiberglass does not burn it will melt if the flame is impinging on it and there are noxious fumes released as well!) This was done with an exhaust fan taking fumes outdoors. The steel needs to be heated until a magnet will not stick to it (around 1600 Deg F depending on the alloy used), then the piece was wrapped in the fiberglass enclosure to ensure it cooled very slowly to effectively anneal it. After annealing it was checked with a file, to see if it was soft enough to cut with the file. Later pictures of re-hardening the piece are the same as picture would be of annealing. (The pictures don't show much, in this case the words will tell you more about what is taking place).

Here, I started by simply knocking off one point almost entirely with the belt sander, and hogging out metal with a dremel tool, hacksaw blade and files. While carving it out I tried very hard to leave as much and as wide a base support under the small lines of the punch to ensure that it would withstand strong hammer blows, without breaking. In the pictures you will see the small files I used. I also used a drill with several small bits for rough shaping. As i went along I had to sand the entire face off a few times to recover from mistakes, the original pattern didn't last very long at all; and that said, the pattern "evolved" as I continued (good thing it wasn't someone else's pattern LOL). It took about 6 Hrs to carve out, along with several small wounds to my hands. Small, round holes became teardrops and ones with curves and square corners. After enough intrigue and pain in my hands I thought enough was enough. I took my stamp and pounded it first, into the end grain of a small piece of hickory and then into the side grain of it until the wood split into three pieces. This was to check the pattern it left and to remove small burrs from it. I then brushed it with a steel brush, thinking now is time for some more heat treatment, this time to re-harden it. 

Re- hardening of the stamp involved re-heating the metal to transition temperature (non-magnetic) and then quenching it in water (I would have preferred using waste oil, but didn't think it would be a good idea indoors). After quenching I tested the stamp using a file for hardness to make sure the file would no longer cut the stamp, it did not cut, but rather slid over the surface removing only a small amount of scale; which put the hardness of my stamp somewhere around RC-60 or harder (hard as a transmission or rear end gear in a truck, or a metal file). Water quenching is very fast, but also puts a lot of stress in the metal, so I tempered the stamp at 400 Deg F in the kitchen oven for 1-1/2 Hrs to help relax stress in the metal or "Temper" it. I shined the stamp up with the wire brush, and moved on to the socket that held it. 

I then took the socket thinking it shouldn't be orphaned, but use it for a guide to hold the stamp so it would hit squarely onto whatever is being marked. The socket was annealed (softened) on the inside, this time with out using the insulation, I simply set the torch so that it delivered heat inside the socket until it got hot enough, then simply let it cool in the air without any draft present. I used several drills to step up to 1/2" diameter, and then used 2 files along with the dremmel tool to worry the inside away until the key would slide all the way through. I then also thought that an index mark (or arrow) would be helpful to position the mark in the desired direction, so I ground an arrow in the punches' end to mark this side up. I set the punch on a small piece of cold steel plate laid on concrete and gave it 14 solid blows producing 14 imprints on the plate. Further inspection shows that no pieces have been launched or chipped out of position; and the punch shows no sign of cracking or other faults!!!