Wednesday, December 2, 2015

My Sharpening Regime

Much has been written over the years about sharpening hand tools and it seems that everybody has their preferred method but much of it seems to me to be trying to design a better mouse trap. A lot of fuss and effort to produce an exact same result as the old traditional method. Some of them are really expensive but do no more than the traditional sharpening method. For instance someone on Gumtree was selling his old sharpening station for $1,800 second hand which still required you to use a sharpening stone and/or strop after you had finished there. 

In this entry I will describe what I do to sharpen and why I use that method. Although I could spend many pages going through all of the various methods devised over the years most people would not bother to read it and this has been done so many times elsewhere.

The principle I adopt is simplicity coupled with tradition. The method I use has been used since time immemorial in both the western and eastern tradition in one form or another. It was the method my dad used and the method I was taught at school will little variation.

It is basically a two step method. A rotating stone for rough grinding to establish a bevel then stones to refine the edge. If you want a super sharp edge then stropping can provide a third step which is useful for knives or razors but I don't bother for hand tools. There may be a pre-first step of linishing for restoring old tools such as in the picture to the left but that is not part of an edge maintenance regime.

Step one is grinding the primary bevel. I do this on a grinding stone on a medium speed grinder. This is often mistakenly called a high speed grinder, it is not. An 8" high speed grinder uses resin wheels and spins at over 6,000 RPM. Your medium speed grinder is the most common type and runs at about 1800 RPM. The best grinder for this step is a slow speed wet grinder that runs at 600 - 800 RPM and runs in a bath of water. This keeps the steel cool and produces a much finer edge but is very expensive and can cost up to $1,000.

The grinder I use is an 8" medium speed grinder and uses a white aluminium oxide wheel. They can be had for $100 for a cheapish unit up to several hundred for a name brand. The white wheel runs cooler and creates a finer finish but does wear more quickly. I use a $20 diamond dresser to maintain a clean wheel and a slightly convex face on the wheel. The convex face will help prevent burning of the edge. I also keep a pot of water next to the grinder and dip the tool into the water after every pass. I set the tool rest angle by eye against the existing bevel, but if I need to reset the primary angle I can use a protractor. I then grind the bevel by hand resting the chisel on the toolrest and continually dipping it in water.

Step two is the actual sharpening. I was taught with oils stones sharpening freehand. Although with careful attention I can still sharpen freehand I find that I get more consistent and faster results using a jig. Since it is not my day job (if it was I would refine my free hand skills) I cheat and resort to a jig. I now use a double sided water stone, 1000/6000 grit. The oil is somewhat messy and requires more careful cleaning so as not to transfer the oil to the wood. If I was super keen I could get an 8000 or 10000 grit stone but I get acceptable results from 6000. This combo stone is about $86 from Carbatech which is pretty good value. Ceramic stones do not require soaking, you just need to spray them with water but they are much more expensive. I use a 400  grit diamond plate to keep the water stone flat. A few strokes after each sharpening is sufficient. I use a $40 stone holder which is quite convenient. I keep a spray bottle of water next to me to make sure the stone is kept moist, especially if I am sharpening a number of tools at the same time.

The jig I use is the Veritas Sharpening Jig Mk II which is $109. It comes with a gauge to set the angle accurately. I also added a camber roller for $38 which allows me to round the edges of smoothing plane blades.

I use a few strokes to establish the secondary bevel at 1000 then flip the stone and apply a few strokes to polish the bevel. If you apply a gentle pressure to the tool then you will not round over the edge. This is one of the biggest mistakes at this stage. Too much pressure may cause the bevel to distort and round over the edge and create a large burr which will produce a less than perfect edge. The burr must be extremely fine, almost impossible to detect. Once the edge is polished remove the tool from the jig and polish the back on the 6000 stone. Job done.

Using this method your ongoing costs are nil. After your initial outlay your grinding wheel, stones and diamond plate should last indefinitely. You do not need the more expensive Veritas jig, your side griping jigs which can be had for under $20 are just as effective if you are careful. You can set up a wood jig with depth stops for your common angles to make setting your bevel angles faster using the side griping jig. Although a wet grinder is better it is a lot more expensive compared to your regular medium speed grinder. The only thing I need now is a dedicated sharpening station. I really only need a small wet area with a laminex bench top set to a convenient height to allow me to lay out my water bath stone lapping plate and jig. If it is relatively close to your working area, but not close enough to get covered in shavings you will be into the semis without dropping a set.

My sharpening resources are;
  • 1000/6000 combination water stone
  • 400 diamond lapping plate
  • Sharpening jig
  • Stone holder
  • Water bath
  • 8" bench grinder with fine white stone
 Also when I get around to it a sharpening station.

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