Harold Hall

Workshop Processes


A less demanding task, but one that is not easily done by hand, is sharpening a flat point screw driver, Photograph 13. After grinding the first side the holder is removed from the swivel base, turned over and the angle reset then the second side ground, this though leaving an edge that is too thin. To correct this the holder is turned through 90 degrees and set at right angles to the swivel base edge and the end ground, the table will of course be set horizontal. The amount being ground off will be controlled by the Y axis traverse, this being increased very gradually until the correct point width is achieved. Photograph 12 clearly shows that additional holes have been added to permit the holder to be mounted on all four sides. These were not included in the original drawings.


Another task for the round tool holder is to hold the diamond dresser, a multi diamond type Photograph 14 or a single point version. Note the piece of oily rag below  collecting most of the wheel's particles. In this case the fence needs to be parallel to the wheel and can easily be set as Photograph 15, the photographs give the impression that the table is tilted but they are horizontal.


Other holders

Photograph 16 shows holders that are used when carrying out simple sharpening tasks on milling cutters having three, four or six cutting edges. These were not included in the original designs articles but the photograph and the examples that follow should make the requirements clear. They are though shown in the Tool and Cutter Sharpening book.


I commented earlier that sharpening the spiral cutting edges of an end mill was for most not a practical proposition but sharpening the end cutting edges can be worthwhile especially as the process is an easy one. Indexing the cutter for each edge to be ground is by mounting it in a square holder that can be moved from face to face.


Photograph 17 shows one edge of an end mill being sharpened by plunging it into the face of the wheel, this being repeated for the remaining edges using the square holder to index the cutter for each edge. In this case the fence has a different task to that used in earlier examples and actually determines the essential angle that makes the end of the end mill concave. This is not critical but in the region of 2 degrees would be about right and is achieved by rotating the table, if using the simpler rest, by rotating the fence on its securing screw. The angle for the primary clearance is set by tilting the table down at the wheel.

Tool and Cutter Sharpening, End Mill