Grinding jig
I grind most lathe tools using a bench grinder. This is equipped with a small grinding rest as shown here which is scribed with lines at 10 degree intervals. The rest height and angle can be adjusted. More details of the grinding rest are here. For normal lathe tools it is easy to set up the rest to have the correct angle and then using the scribed lines as a guide to grind the facets on the tool tip. However, this method is not very satisfactory for grinding threading tools where the angle of the tip must be accurate.
The little jig shown in the header photo was constructed for grinding threading tools. It can also be used to grind other lathe tools if the angle must be exact. The jig is very simple and consists of a piece of 1/8" x 3" steel with a 6 mm square pivoting arm secured by a small M3 socket head screw. The pivot point is very close to the edge of the sheet. The pivot arm can be set at any angle in the range +/- 90 degrees. On the jig shown are two scribed lines at 60 degrees from the zero (centre ) line. These lines are for setting the pivot arm for grinding a 60 degree tool tip. Other lines could be added for different tool angles or thepivot arm can be set using a protractor.
The little jig shown in the header photo was constructed for grinding threading tools. It can also be used to grind other lathe tools if the angle must be exact. The jig is very simple and consists of a piece of 1/8" x 3" steel with a 6 mm square pivoting arm secured by a small M3 socket head screw. The pivot point is very close to the edge of the sheet. The pivot arm can be set at any angle in the range +/- 90 degrees. On the jig shown are two scribed lines at 60 degrees from the zero (centre ) line. These lines are for setting the pivot arm for grinding a 60 degree tool tip. Other lines could be added for different tool angles or thepivot arm can be set using a protractor.
This photo shows the back of the jig. The bar is a stop and guide that runs against the back edge of the grinding rest to keep the jig parallel to the grinding wheel.
This shows the set up for grinding the first face of the tool. The tool is held against the bar with the forefinger and the jig slid from side to side to grind the face.
This shows the grinding of the second face. The pivot has been swung round to the other side.
A very simple jig that facilitates accurate grinding of threading tools.