PREPARING & TYPES
Most of the time when you buy a knife or an axe, they should be sharp out of the box. Sometimes they are not and require sharpening.
As you use your tools to do many a various job out in the wilderness, they will eventually start to dull and go blunt. You may damage the bevel at any time. So this is a short guide on sharpening your knife or axe in the wilderness and at home.
Remember a sharp knife or axe is a safe knife or axe.
Cleaning the blade
If your knife or axe has seen some heavy use, when you've been out in the woodland, chopping and battening wood or cutting materials that can mark or stain the blade, also leaving deposits on the surface. Before you sharpen it, you will need to give them a good clean. You will want your blade to be spotless before attempting to sharpen it as any barrier would make it difficult to sharpen the blade. Also you wouldn't want your fine tools to become rusted or corroded. There are different ways to clean a knife or axe, they may just need a drop of cleaning oil on them or something a bit more abrasive like abrasive paper or a block.
About sharpening stones
When you sharpen the blade, you will be removing some of the metal from it, as you will need to grind the bevel to get the sharpness that you require. The way you remove that material matters when it comes to cutting effectiveness, and there are a number of ways to achieve the desired level of sharpness.
All sharpening stones are abrasive, and harder than the steel or metal of the knife or axe. By moving the blade across the stone you grind away material from the blade, like for like you will wear the stone down as well. Some stones require the use of a fluid or lubricant, normally water or some kind of oil, to make the process easier. There are natural stone and man-made ones.
Most stones are graded by ‘grit’, with a number indicating the grit. The smaller the number the more coarse the stone, there more you will grind down, you only need to use a lower grit if your edge is really bad or a bit damaged. Normally you would start around the 250 mark for knife sharpening and moving on up to around 3000 to 5000 or even higher.
As you progress through the steps you remove some of the scratches/scoring made by the step before and create a uniform cutting edge.
Types of sharpening stones
Whetstones (Oil Stones)
Can be made from natural stone or synthetically using an abrasive such as silicon carbide or aluminium oxide. The synthetic variety are often sold as double sided, with a finer grit on one side and a coarser grit on the other. They are relatively cheap and robust, although heavy. They do not necessarily NEED the use of a lubricant (I use 3-in-1 oil) but this does help with the movement of the blade across the stone and remove swarf (material removed from the blade that may prevent the blade touching the stone evenly or even blocking the ‘pores’ of the stone that have the abrasive effect).
Japanese Water Stones
these are mostly made as synthetic product using naturally-occurring stone and are seen by many as being the ‘ultimate’ way of sharpening a blade – but I’ve personally had as good a result with an oilstone. There is certainly a strong cultural association with these Japanese stones, and there is a whole world of nagura, Shapton, Debado and Ao Toishithat you could dive into if you so wished. The grit sizes range from around 400 up to 12000 which takes you well into ‘polishing’ territory. These stones tend to be quite heavy but robust, and most require immersion in water prior to use (using water as a lubricant – never use oil on a water stone).
diamond has been used industrially for sharpening and cutting applications for a long time now, making use of the hardness of diamond and the relatively low cost of it in granule form. It is usually a coating on top of a steel plate, often with a plastic or resin surround – they often look a little like a cheese grater. These ‘stones’ can be used to sharpen a blade directly or even used to ‘true’ a sharpening stone – i.e. make it back into a flat surface, removing the depression often formed by repeated grinding and sharpening. They do not require the use of lubricant and have a long service life.
high-quality abrasive and polishing papers, often bonded onto glass or flat wood. This is the method associated with the term ‘scary sharp‘ and is inexpensive and simple to master. It works best with blades that have a ‘flat’ bevel and where the whole blade can be run across the surface. It works very well with woodworking tools (chisels etc) but can be modified for use with an axe or knife.
these sharpening kits and items are often one of the above types of stone set into a jig or pre-defined shape. The best types are ones that can accommodate various angles and knife shapes and use good materials – but there are several terrible sharpening kits on the market – beware and read several independent reviews before purchasing if you can.