Friday, 8 April 2011

Sharp Knife Or Blunt Knife?

Friday morning again. Where does the week go? It feels as if the Spring has finally arrived, we have had 20 degrees and sunshine which is lovely. On my cycle in this morning I saw a group of ducklings on the canal which is a sure sign - tiny and very cute.

So, with the sap rising, I always turn to general thoughts about where I am and what I am doing. With respect to shoemaking, I had a thought this week about my knife. Now for those of you who make shoes, you will know how important your knife is. And for those of you who aspire to making shoes, the knife may not seem to be something you would worry over, but let me tell you, your knife is the most important tool in your kit and it can be your best friend or your worst enemy. We shoemakers use the knife all the time, from blocking the insole to building the heel, all day every day. And if it is sharp, life is rosy and all is good in the world. But if it is blunt, then a dark cloud descends and many a curse will be heard from the shoemakers workshop.

Here in England we use a flat steel paring knife for making bespoke shoes. They come in various sizes. The ones we use are about 22cm long and 2cm wide. The image below is from an old Barnsley catalogue who used to make every shoemaking tool you can imagine. Unfortunately things are not so easy any more and you have search a bit harder to find tools these days. You can see that there are lots of different sorts, but the little fella we are talking about is the one with the asterisk. Various sizes were available and we generally used the number 20 or 21. I tried the big monster above but it was a bit unwieldy.




As you can see there are so many other kinds of knives, but I generally only use the plain old flat paring knife.

When you get a new one (they last me about 3 years), you have to spend a good while sharpening it. They arrive very blunt with no real edge.


I use a grinding machine to get me started. This is the only time I use it, as the heat from the wheel does something to the steel and it does not stay sharp as well. There is a technical explanation for this but I do not understand metallurgy! It's called annealing apparently.


On the knife, you are looking to get an angled bevel on one side and the other side must be completely flat. So with a new knife, I only use the grinding wheel on the bevelled side. It should look something like this.





Now the fun bit starts, the hand sharpening. This is the first job which our students do when they start the course and they spend a good part of the first day getting the knives sharp. I can't stress enough how important this is. With a blunt knife you get lots more cuts because you strain much more to get the knife through the leather.

We sharpen our knives using a strop. This is something you can make your self with a piece of wood. It is better to have 4 sides rather than 2 so that you can have different grades of sandpaper/aluminium oxide paper. One surface must have a piece of leather on it. Wax calf is best, but the flesh side of regular calf is fine. Glue it on and rub jewellers rouge into it. This is a mild abrasive and help take off the burrs from sharpening.



You need to glue ali oxide paper or sand paper or electrocut paper if you can get it onto the other surfaces.
To sharpen the knife, you must hold it first on the bevelled side and hold the it at a tiny angle to match the bevel from the grinding wheel. Move the knife up and down the strop in a smooth regular motion. You must press down though. Continue until it gets too hot. Let it cool and start again. You are aiming for an even grind on the edge.


Now turn the knife over and do the flat side. Hold it firmly flat against the strop and move it up and down like before.


After repeating this a few times, place the edge on the leather strip with the jewellers rouge on it and move the edge up and down. This is like what barbers do with their razor and just gives a fine edge to the knife. And that, as they say, is that!


This sharpening routine is something I do all the time. Every few cuts, just top up that edge to keep it super sharp.

This all sounds great and it is how I do it, but I have an admission to make. My knife is not as sharp as I would like. In fact some would say it is blunt. Shameful as it sounds, it is just something I cannot seem to get right and I am so envious of shoemakers with sharp knives. We all have weaknesses and this is mine.
I have tried other things. Diamond sharpeners, wet stones, oil stones, but I just cannot get there. Don't get me wrong, my knife is fairly sharp and gets the job done, but it could be better.

So if any of you out there have a different way, a way that works, any tips to help me, then I would love to hear them. Please!
You know, it feels good to get that off my chest. I can't sharpen knives properly! It is a bit shameful though.

Finally, here are some videos of a Japanese master shoemaker and he has a completely different kind of knife, but it is soooo sharp. I want one! And how does he sharpen it? I think the Japanese know a thing or two about blades. That knife is just awesome! They take a bit of time but are well worth it.

Japanese shoemaker video 1

Japanes shoemaker video 2

Japanese shoemaker video 3