In this post we’ll look at how, with minimum equipment, you can produce a tool with a razor sharp edge. In the previous post I covered different types of Hones.
In order to ‘hone’ your sharpening skills there are three areas you need to master:
- The mechanics of sharp edges.
- The technology of abrasives and the sequence in which to use them.
- The technique of holding the blade so that a uniform edge can be created consistently and maintained with minimum effort.
What is a sharp tool?
Ted Edwards, my woodwork teacher, would indicate the sharpness of the tool by shaving the hair off the back of his arm, indicating, he said “…sharp enough to shave with” (I prefer to try the sharpness of a blade by seeing if it catches on the flat of my fingernail – if it skids, it’s dull). At the time, all I could think of, was why would anyone in their right mind want to shave with a chisel? Of course I missed the entire point he was making, that it gave a sense of what sharpness meant in a very visual way. I also had a Building Drawing teacher that said “Collins that pencil isn’t sharp enough to draw blood…
Anyway – back to Sharpness – a blade consists of two planes that meet at a line of intersection. This sharp edge or angle formed by the meeting of two surfaces is called an arris) traditionally the name for two meeting planes in mouldings).
Although the intersection of the back and the ground bevel looks like a triangle to the naked eye it is not since it has a very small thickness – just a few microns across.
If the edge is wide enough to reflect even the smallest amount of light, it is too dull for woodworking – although probably fine for shaving. If there is no glint along the blade’s edge, then it is sharp.
The edge has three flaws that must be removed by honing:
1. Coarse edge texture.
2. The back
3. The burr.
The most important thing you can come away with from this post is the technique for holding and moving a tool on a stone. Holding a tool consistently and easily is the key to sharpening, and with practice, it’s not that difficult to do and after a few times muscle memory will kick in.
There are a many devices out there that you can buy that hold a blade at just the right angle to a honing stone.
I have several honing guides – but before you rush out an buy one, there are two important things to consider:
i) honing guides allow you to repeat a motion in the same area on the stone, but you run the risk of wearing in certain spots faster and the stone will require more maintenance. (more so on oil and whetstones).
ii) the second problem with honing guides is more subtle: The first time you sharpen you establish some sort of bevel, the second time you sharpen you need to maintain the same exact bevel, if it’s not exact, you tend to create a secondary and then tertiary then whatever comes after bevel at each attempt to sharpen. In fact if you continue this with the same setting, you will actually create a multi-facetted bevel – the change is subtle, and over time, ultimately leads to a curved profile (hard to work with a curved edge).
This process makes for more work because at some point you will need to regrind. Even if you can get the same bevel, setting a blade in a jig exactly the same way is tedious and time consuming.
I find it more efficient to be able to just take a tool and immediately put it to a stone without having to worry about setting up a jig.
As an aside, some make the argument against hand tools that it’s hard to make them work. A hundred years ago and more, people made hand tools work… They had no choice they didn’t have power tools or Hi-Tech guides. Woodworkers were able to be productive by having the right tool and developing the right skills to maintain and use them properly. If you can duplicate that skill, you can be just as productive.
So here’s my 10 minute guide to sharpening using diamond hones:
1) Grind an edge at approx. 25° using a home made jig.
2) Follow this with a Diamond (I use DMT hones)– Extra Coarse (220 grit) – this will fix and restore the damaged edge created by the grinder .
3) Follow with a diamond coarse (325 grit) – this quickly sharpens the edge
4) Follow with a diamond fine (600 grit) – this puts a keen edge on the tool
5) Finish with a diamond extra fine (1200 grit) – this sharpens the blade to a razor edge
between each stage run the back of the blade a few time across the stone to flatten the back and remove the burr (wire edge).
6) Strop with diamond paste (14,000 grit) this will put a mirror finish on the tool. (Come to think of it – my barber uses a strop…) You can also strop using the palm of your hand – do this slowly at first and always pull the blade away from you – after a while you can develop rapid movement.
Technique and stance to hone the blade.
Spritz the stone with water and then standing in a comfortable position (in a planing position perpendicular to the bench). Holding the blade on the stone rock it up and down until you find the point at which a bead of water/oil appears in front of the blade – then lock your elbow (depending on your handedness) at your side and hone the blade on the honing stone in a figure of eight moving back and forward.
If you’ve just done a chisel, block-plane blade or any other chip-breakerless iron you are finished! But if you’re working on a bench-plane, you need to polished the cap iron’s edge that touches the iron. Make sure the cap iron, when tightened in position on the iron, makes complete contact along its entire edge with no daylight showing – this way no shaving will catch between iron and cap iron. Now polish the cap iron surface. How much work depends on its condition. Use the same abrasives starting no coarser than you must. Cap irons usually are not hardened steel and the work to flatten should be quick. Rock and slide the cap iron along the different grits until all coarse scratches are gone and the ‘ramp’ edge looks and feels smooth. Now you’re done!
Resharpen often and lightly, no coarser than necessary, to insure good cutting performance and save time in the long run.
One of my favorite woodworkers is Garrett Hack – check out his honing method.
Happy safe shaving!