How sharp ?

[Alexis1234]

I apologize if this has been covered already- I didn't run across it.  How sharp is sharp enough for a round/ head knife? Yesterday, my knife  chattered/slipped and I ended up with a fairly serious injury while cutting horribly tanned patent leather... I swear it's because the knife wasn't sharp enough. My husband thinks otherwise.   When is it sharp enough and how do you gauge it?  I'm still learning. Thanks for any input.

[Webicons]

When you “think” it’s sharp then it’s not sharp enough.  You need to know that it’s scary sharp.  Sharp enough to slice through a piece of paper without grabbing at all. 

I find difficulty getting a head knife sharp enough to be functional (which is why I choose to use Japanese style knives) but it can and is often done well.  

I’m sure others will chime in and there are quite a number of YouTube videos on the subject. I find that Patience and stropping are the key. 

[Samalan]

the key to sharpening is keep your angels consistent and correct once you have that if the steel is good you should get 8 to 10 stops be four you need to go back to the stone  for a head knife the stone should take no more than two minutes and the same for stropping don't lift  the handle of the knife or you will kill the edge .  all this in my humble opinion . 

[YinTx]

Good steel shouldn't need a stone for a long long time between strops.  As someone said, it should be really really sharp.  Scary sharp is actually what you should refer to a dull knife as.  Dull knives are scary, because they tend to cause injuries.  To give you an idea, I tend to sharpen X-Acto and razor blades before I use them for leather work, because they are too dull.  Never test a very sharp knife to see if it will shave you - if it is sharp enough, it will as easily cut you as shave you.  The paper test is a decent one, - knife should slide through paper without snagging or hanging, with a very clean cut and clean sound as it goes through.  Not quite sharp enough requires a bit of a "sliding" action to go through the leather, a proper sharp one will "push" cut through the paper and change directions easily (ie, you should be able to cut an "S" curve through the paper just by pushing it).

No matter what, always keep your person and all bits of your person behind the blade.   This way, any slip or snag and you are pushing away from yourself, not towards a finger, arm, body, etc.  Hope you heal soon.

Although in reference to kitchen knifes, Burrfection has some youtube videos showing decent sharpness on knifes, and demonstrates paper cutting as discussed above.  You can compare your current knife status to one of his freshly sharpened ones and know if it is sharp enough.  Skip to 6 mins to see knives in action.  Then you can decide if it was the leather, the technique of cutting, or the sharpness of the blade.

YinTx

 

[bikermutt07]

My Knipshield's have yet to see a stone. I've had my french model for about 3 years now, and I only strop it. 

From what I can see with a magnifying glass is a proper sharp edge will not cast a glare. Meaning the absolute edge reflects 0 light. If you can see light glaring from the actual cutting edge it is too dull for leather work.

I can't remember who taught me that. It may have been Mr. Knipshield. 

Most people, myself included, had no idea that when they got into leather they would have to learn how to sharpen. It never crossed my mind in the first couple of months. But, if you want your stuff to look as clean as other's work it takes sharp sharp sharp tools. Not just your knives either. Stitch Groovers, end punches, just about everything needs to be sharpened.

Check out Al Stohlman's " Leather Tools". It is a fabulous reource.

And just accept it upfront, any mass production tools you buy will require finishing on the user end to get them to the final levels of sharpness. This is an industry standard to keep prices reasonable. 

When you buy custom tools, they should usually come in the level of sharpness required.

This is one of the differences between a 60 dollar knife and one that costs over 200.

And keep everything behind the blade. It's a push knife so push it away from all of you.

Good luck.

[Big Sioux Saddlery]

It should shave hair from your arm and make virtually no noise when cutting.  I will say patent is not as easy to cut as other leathers.  The coating on the patent clings to knives, kind of like the plastic sheeting used for harness parts for Biothane harness.  

[zuludog]

There are loads of videos about sharpening on YouTube. Watch as many as you have the stamina for, they will all help to build up knowledge & experience. But if you want to narrow it down a bit Search for 'sharpening a round knife'  I think this one is good -

'How to sharpen your head knife for leather work' by JH Leather Although it's for a head knife aka a half round knife the same method can be used

Starting with a new knife I use a medium oilstone; a fine oilstone; a few grades of wet & dry paper between grits 600 & 2,000; then a strop. Lubricate the wet & dry paper with window cleaning spray.  Now that my knife is sharp I just use the strop most of the time

Tallow & powder, or Autosol will do the job but they're messy. Treat yourself to a proper bar of stropping/honing compound. I use Veritas 05M08.01. A 170g/6oz bar will last you ages  

As well as the cutting edge, hold the knife at a lower & flatter angle so that you polish the whole of the bevel & sides of the knife. This will help the blade to slide through the leather more easily

Edited March 8, 2019 by zuludog

[Alexis1234]

After reading the replies, my knife is no where near sharp enough!  I have stones and stropping compounds, but I struggle with getting the correct angle. 

[zuludog]

1 hour ago, Alexis1234 said:

After reading the replies, my knife is no where near sharp enough!  I have stones and stropping compounds, but I struggle with getting the correct angle. 

Sorry, but the best advice I can offer for that is to watch the videos and practice

As Webicons posted, a Japanese style leather knife is easier to sharpen as it has a straight edge and a more defined bevel. I use both and a Japanese knife will do most things; you soon get used to the asymmetric style. Search YouTube for their use, and Google for suppliers

[bikermutt07]

I broke down a few years ago and bought a Kalamazoo 1x42 belt grinder. It cost me about 300 dollars but it solved so so many problems.

Now all my stuff gets a convex edge and maintaining them is easy with the leather stropping belt.

I still don't use it on my high dollar leather knives though. I'm just worried I will mess them up.

But, all my tools and pocket knives, and work knives go to the Kalamazoo.

And yes, it is an investment for a hobbyist, but a good one to be sure. You will find yourself using it all the time for stuff. And it will outlast it's original purchaser.

I found the learning curve to be short for me. I just ran thru all the cheap pocket and kitchen knives until I had the process down.

Now I use it for wood chisels, strap cutters, all kinds of stuff.