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Here is a jig to set the angle on a dry grinder. It can be made for any angle.
My grinder set up is an 8” half-speed machine with the Veritas tool rest. The wheel is a 46 grit Norton 3X.
Adjusting the tool rest for a specific angle needs to take into account two factors, the diameter of the wheel and the thickness of the blade.
As the diameter of the wheel becomes significantly smaller, it will be necessary to make a fresh jig (I emphasise “significantly” smaller since a little bit here-or-there is not important in the grand scheme of things). The only jig I am aware of that adjusts for different diameter wheels is the Tormek. However the is not enough room to use one on a dry grinder with wheel guards.
Each time the jig is used, it must account for the thickness of the blade. This is done by placing the blade on the tool rest, and then the jig on top of the blade.
Tighten the tool rest setting once it is set up as in the above picture.
The dimensions are not relevant and may be made any size you please. The jig in the picture will grind a 25-degree hollow.
Use a blade with a known bevel angle (say 25 degrees).
Set this up to grind such that it will create a hollow at the middle
of the bevel. To test this, use a felt tip marker (texta, magic
marker) and colour the bevel. Place the blade on the rest and –
with the power off – move the wheel back-and-forth to create a
slight scratch pattern. Adjust the rest until the scratch is in the
centre of the thickness of the bevel.
Retract the blade on the rest until it no longer touches the wheel (you may wany to clampit here so that it does not move).
Place a block of wood on top of the blade and hollow grind that. This will give you a template to reproduce that angle.
Do another for 30 degrees (and any others you wish).
Regards from Perth
Derek
December 2008