Grinders for sharpening woodturning tools

Draper 6 inch grinder

I use a 6" grinder like this Draper

High-speed double-ended dry grinders designed for metal machinists are used by the majority of woodturners - perhaps because they are inexpensive and easily obtainable.
A machine with 6" diameter stones is the smallest machine you should buy. 5" grinders can be underpowered, and the small radius of curvature will produce an excessive "hollow grind" on the tool bevel. An 8" machine is very nice but might cost quite a bit more and the added benefit is not great. My advice is to buy a medium priced far-Eastern 6" grinder and invest in better grinding stones. Grinders generally come with two poor quality grey coloured grinding wheels, one coarse and one fine. You should change at least one of these for a cooler cutting wheel or you risk damaging your expensive tools by overheating the edge.
Choosing a suitable grinder Other grinders

Record RPBG6

Record RPBG6

This Record 6" grinder has a fine white wheel which is extra wide (40mm). Ideal for skew chisels but primarily intended for cabinet makers tools such as plane irons. Woodturners would need to fit a harder fine wheel on the right for gouges and other curved blades because the white wheel would go out of shape if used for frequent grinding of gouges. A five year guarantee is included with this grinder. Record RPBG8

Record RPBG8

This larger and more powerful 8" grinder also has a fine white wheel which is extra wide (40mm). The 8" wheels will give less curvature on the bevel of the tools. Woodturners need to fit a harder fine wheel (preferably microcrystalline) on the right as with the smaller grinder. With five year guarantee.

Wet grinders
Tormek wet grinder You might well be tempted to buy one of the slow running wet grinders especially if you do a bit of cabinet making and you need to sharpen plane irons and other wide carbon steel blades without any risk of "burning the edge".
These machines do a fine job and will give a superb razor edge to all your tools. However for sharpening woodturning tools they have some significant disadvantages

Half speed grinders
The idea behind these is that the motor running at 1500 rpm instead of 3000 rpm gives a more controllable progressive cutting action with less risk of overheating the edge. You may be attracted to these machines but you will find that they are very expensive and that it is cheaper to fit a cool running fine wheel to a standard grinder and this will give just as good a result.

Sorby Pro-Edge System
Pro EdgeThis is more accurately described as a linisher. It is a complete system with jigs included which will sharpen all turning tools and cabinet makers tools as well. Click here for the Pro-Edge Page ProEdge system

About upgrading grindstones
Fitting jigs to a bench grinder.