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Harold Hall

Workshop Processes

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The table can be pivoted in the case of the complex rest but with the other the fence is swung left and right for the same result. The purpose of this is to ensure that the part being ground will pass the corner of the wheel Sk. 1A and not collide with it  Sk. 1B, this being very important. The angle is not calibrated but is relatively unimportant, 1 to 2 degrees being about right.

 

Both tables can be tilted left or right and or towards and away, again these are independent in the case of the complex rest but both provided by the ball joint in the simpler one.

 

In the case of the complex rest the guide fence can be mounted in line with the X axis or removed and fitted in line with the Y axis. With the other the table rotates using the ball to determine which axis the fence aligns. In both cases the fence has a removable stop which can be fitted when the tool being ground must be stopped precisely. Typically,  when grinding a slitting saw and the wheel must be prevented from touching the adjacent tooth. The precise stop position is controlled by the X or Y feeds as is appropriate for the setup being used.  

 

ACCESSORIES

Swivel Base

This is one accessory that is used as an accessory to most of the others and can be seen centre front in photograph 1. Its purpose is to set one of the angles being ground onto the tool, the other two, when required, are set by tilting the rest's table.  Above, it was explained that the fence controls the angle at which the part being ground skirts the corner of the wheel but this device controls the angle ground onto it. Sk. 2 should make this clear.

 

Square tool holder

This is used mainly for lathe tools but is not limited to these, but as there are normally three faces to be ground on a lathe tool it is a good choice for showing  the rest being used. I should add here that the article is just about using the rests but does not cover in detail the angles required, if the reader requires help in this direction then the book “Tool and Cutter Sharpening” number 38 in the workshop practice series would be a starting point.

 

There are two stages in producing a lathe tool, rough grinding the shape and then finalising the cutting edges. Obviously, shaping the tool is a once only task after that it will be just resharpening. Except for small, such as those in photograph 2, and or complex shaped tools, initial shaping will be done free hand, as will the tool being illustrated in this example. I will therefore start at the point that we take over from the pre shaped tool.

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