Bespoke Shoes Unlaced – a shoemaker's blog

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

28 comments:

JSM said...

You're having trouble with the grinder because the heat ruins the temper of the steel. The solution for this is to grind at low speeds, and using a coolant. The cooling fluid can be anything from oil to water, and there are also specialised cooling fluids available.

If you do get the steel to hot, even if you use the grinder just for a little while, you might already have ruined the temper - and in essence you're then stuck with a ruined knife.

Li Sashay said...

Thanks! This is a great blog post! Really good info here and I love the photos.

jimmyshoe said...

Thanks JSM, sounds convincing. The thought of sharpening a new knife completely by hand is a bit daunting though.
And thanks to you Li Sashay as ever.
Best, jimmyshoe

THEASSMAN said...

it is easy to control the heat at the grinder. Keep a container of ice water next to the grinder, grind slowly and dip the blade into the water as soon as it becomes warm. This will preserve the temper of the steel. You should also look into Japanese woodworking knives. they have a similar form factor to yours, but are made of extremely high quality laminated steel (which stays sharper longer) and they are always delivered (as are all Japanese blades) razor sharp.

jimmyshoe said...

So it seems it's that pesky grinder then. And where do I get these wonderful Japanese knives? Any clues? Thanks for comment, jimmyshoe

DWFII said...

It is the grinder. The old foot pedaled grindstones moved slow enough that the risk of de-tempering your steel was much minimized.

Suppliers of woodworking tools, etc., often sell slow speed grinders (still moving faster than foot pedaled) which enter a water bath as they rotate. That's the answer.

If you get a blue spot on your steel the metal has lost its temper and will not hold an edge. It is possible to re-temper the edge/blade but otherwise the blade must be re-shaped and the blue completely removed before it will be a functional knife again.

I'd like to know where to get the Japanese knives myownself.

jimmyshoe said...

Right on DWFII, where do we get our hands on these Japanese knives?
And assuming we get one, how do we sharpen it the Japanese way? jimmyshoe

DWFII said...

I did a search for "japanese woodworking knives" and came up with several places to order knives. some of these can be quite expensive...closing in on $300.00. But the laminated knives are far more reasonable.

Try this site: http://tinyurl.com/3wwr2gz

here

As far as sharpening them...the same site has an article on how-to. http://tinyurl.com/3qrvyoz

here

But I think a series of stones would probably be the best bet unless you're willing to pony up for a Tormak or something very like it. That said, from what I understand they come incredibly sharp.

Isaak M said...

Here's a source for Japanese style leather knives:
http://kawazairyo.shop-pro.jp/?mode=cate&cbid=33651&csid=7

I can't speak to how good of one it is, as I've not used them myself, but at least it can serve as an idea of what's commercially available in Japan.

Hope that's of interest.

jimmyshoe said...

Thank you Isaak M, I will check out the link. A lead at last!

Ludvig said...

This might help http://www.handtools-uk.com/product_info.php?cPath=24&products_id=752

Ludvig said...

Source fore the Japanese knife http://www.mehr-als-werkzeug.de/product/710714/Japanese-Leather-Bevel-Knife/detail.jsf

DWFII said...

James,

I have one of the Japanese leatherworkers knives...it was given to me by a Japanese student...it is very sharp and seems easy to keep that way.

I did a search for Japanese woodworkers tools and came across several sites. Some of these knives can be extremely expensive...topping $300.00. But others are very reasonable...it depends on how they are made--laminated or Damascus, etc., and how famous or well respected the blacksmith is.

As for sharpening I suspect that since they are scary sharp right out of the box, just regular honing and so forth is all that would be needed.

Here are links to two sites...the first for the knives the second for instructions on how to sharpen them:

knives

sharpening instructions

I intend to purchase one or more of these knives myself.

Hope that helps.

jimmyshoe said...

Thank you for that Ludwig, jimmyshoe

jimmyshoe said...

Here is a comment by DWFII which got lost in the ether. So thank you for this, jimmyshoe

I have one of the Japanese leatherworkers knives...it was given to me by a Japanese student...it is very sharp and seems easy to keep that way.

I did a search for Japanese woodworkers tools and came across several sites. Some of these knives can be extremely expensive...topping $300.00. But others are very reasonable...it depends on how they are made--laminated or Damascus, etc., and how famous or well respected the blacksmith is.

As for sharpening I suspect that since they are scary sharp right out of the box, just regular honing and so forth is all that would be needed.

Here are links to two sites...the first for the knives the second for instructions on how to sharpen them:

http://www.japanwoodworker.com/dept.asp?s=JapanWoodworker&dept_id=13221

http://www.japanwoodworker.com/page.asp?content_id=6111

I intend to purchase one or more of these knives myself.

Hope that helps.

DWFII said...

James,

Thanks for posting that.

I might add that further investigation has revealed that these Japanese woodworking knives are roughly 3/16" (5mm) thick at the spine. Much thicker than Barnsley knives.

I have also been told that they need a water stone to sharpen.

JSM said...

The Japanese like their waterstones, but they're by no means needed - you can use any other sharpening implement instead. That being said, they're great stuff, if you are patient, with grit numbers going into the tens of thousands. And they often cost a pretty penny....

Anonymous said...

What grits are you using for sharpening?

My suggestion for achieving a sharper edge would be to use 1000/6000 combi waterstone before leather strop. Real natural waterstones cost quite a lot, but man-made ones work fine, too. Also, skipping the grinder, at least without cooling, seems like a good idea.

One thing that still remains a mystey to me is the sharpening of curved knives. Does anyone know of a tutorial?

DWFII said...

High carbon steel skiving knives Redux

At the risk of flogging a dead horse (I hope not)...

After talking to the very nice folks at JapanWoodWorking and explaining our needs, and why the woodworking knives were probably too thick, Jack sent me this link:

http://www.hocktools.com/Knives.htm

Now these look pretty good. And they are just a tidge over 2mm thick.

Also here's another sharpening tutorial that has some good information.

http://www.hocktools.com/sharpen.htm, sharpening

Rb said...

hi, I’ve mentioned this on another post you wrote about sharpening but I use 3m lapping film that they use to polish lens with. I use the 0.3 micron on a glass plate rather like a strop.

I use to use a strop but I got fearful that the cutting edge was slightly rounding due to the fairly sizable give in the surface.

Either way I’m not likely to move off lapping film for some time. Brilliant stuff.

Really enjoyed your post!

jimmyshoe said...

RB, I have never heard of this stuff, but it sounds interesting. Where do you get it? And any images of your method? Thanks for commenting, jimmyshoe

William de Wyke said...

Others have pointed out that the grinding will be destroying the temper on the edge of your knife. A water-cooled grinder is the Right Tool for solving this problem if you want a powered solution, otherwise a DMT diamond stone will let you remove a lot of material, fast, without heating the blade up too much. Always grind and dip into cold water though, even grinding by hand.

For honing, you can't go past the 3m microfinishing abrasives on glass. Lee Valley Tools sells them - www.leevalley.com along with everything else you need to get your knives scary sharp. They also sell a 1" belt grinder and a very cunning adjustable tool rest that will allow you to grind perfect bevels without difficulty.

I'd recommend everyone who has to use edged tools read two things: Leonard Lee's _Book of Sharpening_ (available from Lee Valley) and Brent Beach's sharpening pages - Google "Brent's Sharpening Pages". They're geared towards plane irons, but his technique can be modified for almost any tool. He's where I first heard about the 3m abrasive sheets.

Lastly, those japanese leatherworker's knives are available from here:
http://www.japanwoodworker.com/dept.asp?s=JapanWoodworker&dept_id=13230

Hardyhell said...

hello,

has anyone bought a japanese knife yet and could talk about how good they are and how to use it.they are completely different shaped than the european shoemaker knives.
i am thinking about to buy one from japanwoodworkers.

greets

hardy

Menseffects said...

Thanks for sharing us great blog about difference between sharp knife and blunt knife. I always like to buy sharp knife then blunt knife.
Out Of Front Knives

Reuel said...

Great instruction. However, which side is the bevel for right handed knife? Is the bevel facing the last when you cut the outline of the sole or heel of the shoe. Is this knife used for skiving as well or A different knife with different bevel side is used?

jimmyshoe said...

Hi Reuel, the bevel is shown at the top of the post. And when cutting the sole, the bevel is against the leather. And we use the same knife for skiving. Some people use a curved knife but we don't. It's whatever you find easier. Best, jimmyshoe

TM said...

Just checking in to see if anyone's purchased the Japanese Woodworking knife yet... I'm looking for a sharp skiving knife ... it's a difficult to find ...
Thanks!
TM

jimmyshoe said...

We haven't but we hear nothing but good reports about them, so a good choice most likely. Best, jimmyshoe