“I have been thinking of making a hidden-tang knife with a blade made by one of the companies that advertises in BLADE®. However, that leaves a problem. Most of the blades in question have either a small tang, which causes a possible stress point, or a traditional-shaped tang that seems very short. Which is better and why?
“I also have seen hidden tangs cut out of full-tang knives; how can this be done without affecting the temper?”
Let me start with the second question about converting a full-tang knife into a stick-tang- or a so-called hidden-tang knife without affecting the temper. If this is what you would like to do, it certainly can be done without damaging the blade or losing the temper.
While most factory-made blades are fully heat treated, tang and all, you do not need to be so worried about softening the tang. This area could just be spring hardened. But, as you know, it is very important to not let the heat travel up into the blade and soften it.
You will need a bench grinder or a belt sander, or you can even use a disc grinder. Any will do. Whichever machine you happen to have or choose to use, the main thing is to not overheat the material while working it.
To ensure this, you will need to use a coarser grinding stone or a new sanding belt not higher than 60 grit. A fresh new belt is essential for the operation. The sharper the belt, the less friction/heat will occur. A duller belt will create a lot more heat.
Another thing to watch for is to not apply a lot of pressure when you are grinding. Again, the more pressure, the more heat.
Besides using a sharp belt and light pressure, after each pass on the grinder be sure you cool off the blade completely by dipping it in cool water. If you want to get fancy, you can place the blade on a piece of dry ice to cool it, though it is not necessary to go to such lengths.
One obstacle when converting a full-tang knife into a hidden-tang one is the pin and glue holes. The size and placement of the holes will dictate the shape of the tang and obviously the handle shape as well. Consequently, you are limited as to what you can do.
One last thing to watch for is to not grind too close to any of the pin or glue holes because this will be the fault or weakest point of the knife. (See Figure 1.)
As for your first question, both the hidden-and full-tang style of knife construction have been serving mankind for hundreds of years, so I would not consider one more traditional than the other.
Concerning which type of tang is better, it is up to individual preference. The properly prepared tang, either full or hidden, will perform well. A well-constructed hidden-tang knife should have no stress points. (See Figure 2.) A stress point can occur during heat treating if the juncture where the blade and tang meet has sharp corners. (See Figure 3.)
This juncture is where you need to pay more attention and take care to avoid creating sharp corners and edges. A full-tang knife also can have stress points if the drilled holes are not slightly countersunk to eliminate sharp edges.
You mentioned that some of the tangs appeared short in the advertisements you have seen. They say a picture is worth a thousand words, but sometimes a picture does not do justice or give you a true measure of the proportions of the subject.
While checking out all the pictures and blade designs available, you may have missed the information written under each picture. Each picture has the overall size and the blade size. If you take away the blade size from the overall size, you will end up with the exact measurement of the tang.
I am happy to hear you are going to try making a knife from a kit or a factory-made blade. Everyone needs to start somewhere. Maybe it will lead you to try making your own knives, too.