Carving Know-how: Sharpening archive
Thursday 26 July 2012
Peter Benson demystifies the tool sharpening process
There is probably more written about sharpening than any other aspect of woodcarving. Why is it then, that the most common problem any carver experiences is how to keep his or her tools sufficiently sharp to produce work of a high standard?
I fear that the real problem is that there are so many different ways to sharpen tools and so many conflicting ideas about which is the best method that the average carver has no idea what to do for the best. Any written information tends to be rather technical and can often frighten the carver, making him or her reluctant to embark on a process that they fear will do more damage than good and be time consuming as well.
Identifying blunt toolsSharpening does not need to be a daunting process at all and it is really better to get it almost right than to allow the tools to sink deeper and deeper into the depths of bluntness and inefficiency.
I have seen so much carving that has obviously been very carefully completed and has taken a great deal of time and effort yet has a resulting finish that cries out, â€˜blunt toolsâ€™. This is a shame because this can be easily avoided.
Most manufacturers nowadays supply their tools already ground and honed so that they are ready to use. Unless you are an experienced carver I would recommend that you avoid any tools that are not ready to use in this way. It is very easy to see if a tool has been honed by looking at the bevel. A ground tool will have a dull bevel with marks left by the grinding wheel or stone. A honed tool will have a very flat, shiny bevel with no obvious grinding marks. It will also be sharp enough to cut wood easily.
One of the problems carvers face is that many of them donâ€™t know when a tool is sharp and when it isnâ€™t. There are many recommended ways to test a tool, but the best in my opinion is to hold the tool lightly in a pencil grip and try to cut along an end grain corner of a piece of wood. If a continuous shaving is produced with little effort, the tool is sharp. If this is difficult, the tool is blunt.
HoningAssuming you are starting with a new tool or one in reasonable condition, honing can be very simple and it gives several options for which method you use. They all work, but you need to find one that works best for you. Initially I suggest that you concentrate on a honing method that you can manage effectively.
The options are fairly simple; you can do the job manually with a leather, webbing or MDF strop or you can choose from the wide range of power honing systems that are on the market. Unfortunately, these tend to be rather expensive and choosing the right one for you can be a bit daunting. They all do the job, but some more easily than others.
The method I recommend, certainly until you find something that you prefer, is a cheap, small bench grinder from your local DIY store, modified as below. The smaller machines â€“ 150W is powerful enough - will do less lasting damage to your tools.
Customising your grinderOnce you have purchased your grinder, reverse the direction of rotation so the front face of each wheel is moving upwards rather than downwards. With the motors used nowadays, the average person cannot do this electronically so there is no need to undo or change any of the wiring. What you do have to do is remove the cross head set screws that hold the motor to the base, turning it through 180° so that the openings in the shrouds are at the back. Reattach the motor to the base and change the complete shrouds end-for-end, bringing the openings round to the front. Your grinder is now as it was before, but rotating in the opposite direction.
You can, of course, carry out the next stage while the shrouds are being changed over to save dismantling twice. You need to remove the outer shroud casing together with the grinding wheels. Discard these wheels and replace them with a 100mm diameter close-stitched rag wheel at one end and a 100 x 25mm medium felt wheel at the other. Remember that one holding nut is the right hand thread and the other is the left hand. Both these wheels will need to have the centre holes enlarged so that they will go onto the spindle. You may have to juggle with the washers for each wheel to get them to run in the centre of the shrouds. If you put the leather washer on one side of the rag wheel to the outside, you can tighten the holding nut directly onto it without a separate washer.
The hard work is done; you just have to set the sharpening angle of your tools. If your grinder has an adjustable tool rest, you only need to adjust to the correct angle. If not, you can find the angle you need by carefully placing a tool with the angled bevel that you want on the tool rest with the bevel resting flat against the surface of the wheel. Put some modelling clay on the rest and press the tool onto it. This will give you the angle you need. Cut a small piece of wood to this angle and stick or screw onto the rest. You now have your honing guide and can be sure that you will be honing all tools to the same angle.
I generally use the felt wheel for flat chisels, shallow gouges and V-tools and the rag wheel for the rest as the angles tend to differ. You must keep the safety guards in place at all times.
You will need to dress both wheels with a polishing compound to get the best results; it acts both as an abrasive and a coolant.
Using the new systemThis system will do pretty much everything you need to keep your tools well honed but only if you use it regularly. I reckon that I hone a tool every half an hour of use. This takes about ten seconds and I am back carving again. The longer you use a tool without honing it, the more time and effort you will need.
In the next article I will tell you how to hone by hand, ways to improve your system and deal with more complex tools. We will also cover some dos and donâ€™ts when repairing and restoring tools.