First off, lets make a difference between a sharp blade and a polished blade:
- Almost all blades are manufactured as “sharp” blades – that is, they come with the correct angles to their blades – roughly a 48 degree combined bevel as shown in the illustration below.
- A polished blade is where those beveled edges of the blade has been stropped and polished to remove TWO things – the grinding marks from when the blade was manufactured and secondly the residue that builds up on the blade from the leather.
This means that sharpening a blade is seldom necessary. I used my first swivel knife blade for more than twenty years before the stropping so deformed the shape that I had to put it on a grind stone and just reshape it again.
When you buy a new blade, here is what I suggest you do:
- Spend at least half an hour stropping / polishing the blade as shown in the following video (card board with jeweler’s rouge on it works just fine).
- Then you can start with it on the leather.
- Every time you pick up your swivel knife to use it, strop it for a few minutes.
- If you do a lot of work with it, strop it every five minutes. After a while, you will get the feel of a blade that is gliding through the leather as if it is cutting through butter, and a blade that “stutters”. As soon as it cuts with jerky movements, you know it needs more stropping.
I hope this helps – please contact me if you have any more questions.