Editor’s Note: This is an excerpt from Murray Carter’s new book, Bladesmithing with Murray Carter. Click here to learn more from this renowned knifemaker.
The shape of the blade, or profile, must be precisely ground. Grinding is the operation of using files or other abrasives to mechanically shape the steel into a functional blade.
Grinding can be divided into two categories: grinding the blade profile and grinding the blade’s edges (secondary and primary).
Let’s talk about the profile. Grinding a forged blade’s profile can be done with a variety of tools. Heating the blade via friction is not a big concern because this grinding is done prior to heat treating (annealing, quenching and tempering). As you may know, the blade needs to be shaped after a pattern or template. At this stage that template is scribed onto the billet of steel that is to become your knife.
Place the pattern so that it most appropriately covers the billet in relation to the thickness and tang. Be careful on full-tang knife billets to orient the template the correct way. I once made the mistake of switching the tang end of the billet for the blade end and wound up with a blade with way too much taper.
Once the template is in place, secure it with a pair of locking pliers or strong clamps. Any sharp-pointed tool that is harder than the annealed steel will scribe (scratch) lines onto the billet. Trace around the template completely. Examine it before you remove the clamp(s) to make sure you can see the scribe lines clearly. Examine it again, checking it against this list:
* Are the lines clear and not making little “train tracks?”
* Is the blade/tang junction exactly where it should be?
* Is the blade where it should be?
* If you have made a mistake scribing the lines, you can lightly grind the surface and scribe again, but you will now be committed to grinding and polishing the flats of your finished blade.
Also remember that, on a laminated billet, if you grind steel from one side you really ought to grind the same amount from the other side as well, or the steel core will no longer line up in the middle. For blades
that are meant to have a forge finish or a hammer-forged finish, these options will no longer be possible, so take great care when scribing lines on a billet.
There are several methods for removing the excess steel from the billet to produce the perfect profile.
* Steel shears
* Cut-off wheel
* Band saw
* Drill press and hack saw
* Belt sander
* Bench grinder
* Kaiten toishi
As the smith is cutting out or grinding the blade profile, the scribed lines, which should be clearly visible, are the guide. As soon as you are so close to the lines that you are actually touching them in places, it is necessary to employ another “micro observation” technique to be in full control of the profile.
In a good source of natural light, hold the blade at eye height with the flats of the blade horizontal. Instead of focusing your attention on the flats, look closely at the outer edges of the blade. If you hold the blade with the point towards your eye, the spine of the blade should look compressed into a few millimeters.
Compressed like this, every high or low spot on your scribed line will be evident. Similarly, every line on the outer profile of the blade should be examined this way. In the pattern or template you used, every line should be well defined and with a purpose. Ask yourself if the lines you are now looking at were meant to be perfectly straight, curved or pointed. Pinpoint trouble areas, then attempt to grind in a way to affect only those areas and re-examine.
At this stage, the blade should be at 97 percent of its final profile. The other 3 percent will be removed in the final polishing stages.
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