Consequently, the existing rest is removed and the new one replaced using the same
fixings, but as grinding machines vary so will the fixings for the rest. Having studied
quite a number of the lower priced grinders I find that many use the same method
to secure the rest. Because of this, the method I have used will suit most other
makes, only the dimensions of one part need changing. Later though I have suggested
an alternative, and time saving, method of mounting the rest.
The two angles mentioned above are the primary clearance (P) behind the cutting edge
and the angle of the edge that results in the end of the cutter being concave (C).
The clearance angle should be in the order of 5° but this is not crucial, if though
it were increased appreciably then the edge would be finer and less strong and become
blunt more quickly. The angle is achieved by the table being 6mm below the wheel's
centre and with the cutter held in a 25mm square holder results in the cutter's edge
being 6.5mm above the wheel's centre. This giving nominally an angle of 5° based
on a 150mm diameter wheel, see the main assembly drawing.
The concave nature of the end mill is by positioning the cutter at an angle of 1
to 2° relative to the wheel and is achieved by setting the body (4) to this value.
Whilst it is essential that the end is concave, precision is not required and lines
scribed onto the rest give an adequate guide for setting up the angle.
Not only is it essential that all four edges are sharpened to the same level but
also that the amount being ground off can be controlled to the minimum necessary
to remove the blunt edges. In achieving this the life of the cutter will be increased
by allowing it to be sharpened a number of times. Because of this the device provides
a stop that
can be adjusted in steps of nominally 0.025mm (1 thou)
This is a simple part but I have on the drawing suggested an alternative size for
the angle to that which I have used and which the reader may like to consider using.
When using the 50mm wide angle the cutter holder (1) projects beyond the edge of
the table though there is sufficient support for it to stay there unaided. Because
of this 60mm wide angle could be used but is by no means essential. It will though
be necessary to use black angle and machine the working face.
Photograph 2 shows how I set up the angle for machining the ends but this is not
essential and leaving them as sawn would be a time saver. Photograph 3 shows the
slot being made. Drill the two holes B but leave hole C till after the support has