Sharpening Wood Tools
Sharpening Wood Chisels - Critical to a quality finish, effective, efficient and safe cutting.
(best modern chisels Pfiel swiss made, failing that Old wood chisels are far superior to modern chisels - Needham Market Nr Bury St Edmunds Toolshop Auctions is a good source, go for "Prize medals"
Grinding
The angle of grinding is dependant on the hardness of the material to be cut and the amount of material to be removed, but it is approximately 30 degrees (see DRG 1/2/3)
During grinding the chisel will get very hot due to friction this is normal. The chisel should be quenched repeatedly in water to stop it from getting too hot. If this happens the chisel will go a blue black colour at the very tip, which means that the temper and therefore the hardness of the chisel has been affected adversely. Too avoid this constantly move the chisel from side to side, never allowing it to rest on one spot also turning the grinder off and allowing the slowed speed of the grinding stone to grind the chisel will help.
Sharpening
Various stones etc can be used with various properties, the important point is that one is using a comparatively coarse abrasive first moving towards a very fine abrasive at the end where the chisel is being effectively polished to achieve, if not surpass the sharpness of a scalpel blade.
From the ground chisel one is initially trying to refine the coarse grinding marks and prepare the groundwork for the finer stones. As a general rule one is trying to achieve a small 'Burr' across the full width of the chisel. Breaking off of this burr by the fingers will ruin the cutting edge and it should only be removed at the last stage i.e. stropping. Wood chisels are normally sharpened on one side only, Drg 4 shows incorrect practise
The sharpening process is a two handed process, pressing firmly on the chisel and using the full width/length of the stone (see Drg 3 for good practise). As a matter of Interest Drg 6 shows the method used to sharpen gouges.
The chisel tip should ideally be straight across see Drg 7 the first diagram, all the other are usually incorrect (unless specifically required) and will adversely affect the handling/use.
Stropping
This is the final process using a Leather with a very fine cutting compound (metal polish normally suffices) on it (see Drg 5) drawing the chisel towards you and pressing down firmly. After a few firm brisk strokes turn the chisel over and repeat, etc etc after a while the burr will start to come of, avoid the temptation to break the burr of and continue polishing. The edge produced will now be very sharp, a few quick strokes on the strop will restore cutting edge during use for a while, until returning to the sharpening stones becomes necessary.
