Engraving Metal help

[crockett]

I'm trying to build a PC folder with a spring. I've done about a half dozen friction folders-a couple with spring (dorsal) tops but the spring backed knives are a whole different thing- really tight tolerances and it has been a lot of work.
Now I am dealing with how to create a nail nick. A modern nail nick is flat across the top and curved on the bottom but the knives of the era seem to have a curvature on both top and bottom. I was thinking about a key hole saw set at an angle- that might duplicate the mark but I tried making some jigs and nothing seems to work. Now I am thinking about using some engraving tools and make a template to mount on the blade.
I think historically the blades were forged and during the forging a cutler used a stamp to mark the nail nick- quick and easy. Sometimes I am amazed at how much work must be done to re-create what was historically an easy task- for example I ground the blade to have a continual taper from shoulder to tip.
In any event, any suggestions appreciated. If I can't figure out how to do it- might just forget the nick altogether but I would like to have one if do-able. The other thing is I wanted to make several pc folders with springs- this first effort has integral shoulder and heel bolsters- all iron but the next one I wanted to do an iron liner with applied iron bolsters- the next folder- I want to do some metal checkering on the bolsters so I'll have to get involved with that in any event.
Still learning- or at least trying.

 

[LRB]

With a steady hand, you should be able to do it with a Dremel and a mizzy wheel, or Dremels abrasive cut off wheel.

 

[Nifeman]

With a steady hand, you should be able to do it with a Dremel and a mizzy wheel, or Dremels abrasive cut off wheel.

Or, you could use a drill press with a dremel cutoff wheel. Don't forget yer safety glasses...Bud

 

[crockett]

Well I made a jig, it consists of two metal plates set 1/2" apart with slots in the shape of an upside down T - the slot width is equal to the diameter of the cutter's shaft (1/8"). The cutter stars at the top of the upside down T and then is moved down into the material and then from side to side. I have collars on the shaft of the cutter so it cannot move forward or backward.
I did a series of practice runs on aluminum. Some okay and some not- so I am concerned on doing the real thing. If I stay with this jig I'll need to practice more. I'd still prefer a better way to do this job and I'm open to suggestions.
I guess I'm learning why there aren't too many hobby knife makers that make spring backed folders. No hobbyist is going to spend $1,000 plus on a milling machine. Still, I always like facing problems of this sort and figuring out a way to do the job.

 

[crockett]

P.S. the cutter is a Dremel #125, an angled cutter. This gives a 90 degree cut on top and a sloped cut on bottom- the cutter is at a right angle to the work. The diameter of the cutter creates a more shallow cut on the ends.

 

[crockett]

Well I did the nail nick. It's "okay", acceptable but I think it could be better. There are some milling marks I'd just as soon smooth out. On other forums I tried finding out a way to make a nail nick without the expensive milling machine, and no one had an answer. I didn't realize it but most of the modern folders have either a straight slot or a thumb-bob, the nail nicks are getting to be a "yesteryear" thing.
In the interest of being pc- if I continue on with folders, I think the only way to do it is how they did back at the time, get a stamp and stamp the metal while it is cherry red- The only problem is knowing what steels I can and can not do- if it is an air quenchable- I may harden the steel and not be able to work it there after. Probably best done with 01, etc.
A guy in Sheffield said they stamped the nick before doing anything else- if they screwed up- it was only on a blank, not a finished blade. I figured I'd do the same on the next knife- at the start.

 

[LRB]

The 01 will also slightly air harden, but nothing like A2.

 

[crockett]

Wick- is 01 a good choice or is there a better and if it does air harden a little should I anneal after heating (stick in vermiculite, etc)? Thanks.

 

[LRB]

You will have to try it and see if it gets too hard for you to work. It hardens some, but maybe not too much for what you will be doing. I would strongly recommend a stress relief though. That will reduce warp in HT. Ideally, 1250° for an hour. Punching in that nick will probably make it want to curl from both ends. If you feel a need to anneal, you really need a sub critical anneal to re-spherodize it. I don't think you would need to however. Just a good stress relief should help. If you haven't noticed, you can hand straighten 01 blades for about 5 minutes out from the quench, while it is just cool enough not to burn your hands. You can have even more time to straighten if you can judge the temp to be somewhere under 400°. You might run a test blade and see what happens before you do anything extra. You may only need to straighten a little.

 

[crockett]

That was one concern I had on the nick. I did a post-1840 blade one time with a gut hook where I beveled the gut hook on one side and that small difference caused a slight bend when I heat treated it. I think the stress relief is a very good idea. Thanks.