C - Grinding Advice - GRAVOGRAPH CG30 Guide D'utilisation

c - Grinding advice

The following precautions are recommended to prolong the life of your grinding wheel :
• select very small cutting depths.
• use the whole of the grinding surface on the wheel so it is kept smooth (vital if you want good results).
Do not grind carbide cutters on a corundum wheel however to obtain a mirror polish on your steel cutter, finish off
using a diamond wheel.
Regrinding the flat end
The flat end has a cutting angle of 0°. It is possible to go below this : diameter/2 = - 0.05 to ease the removal of marks
and allow you to salvage old cutters.
However there is a high risk of permanently damaging the cutter.
You can not use it for shallow grinding or for a tip greater than 0.75 in diameter.
You can also smooth the median side using an India stone.
Regrinding conical cutters
A cutting edge clearance is imperative to obtain optimum cutting power and perfectly finished surfaces, there must
be a reasonable tool clearance angle (see chapter entitled "Type of cutter and average clearance angle").
During grinding, the tool holder will gradually move closer to the grinding surface of the wheel (do not force it against
the tool-holder or jerk the machine when creating facets). This process occurs with a simaltaneous180° rotation.
This combination of movements will give you consistent passes and prevent decarbonization, burning or charring
of a steel cutter, all of which ruin the instrument.
The clearance angle should be perfectly regular to produce an sharp, even cutting edge.
After creating facets the tool holder must rotate until it stops.
The rake angle is automatically produced. It should be perfectly regular, with no facets as these will appear in the
engraving.
A small piece of the cylindrical part of the rod should be visible to the eye (see page 58).
For extremely fine engravings an India stone can be used on every part of the cutter.
Regrinding cylindrical cutters
The length of the cylindrical part must always be one and a half times the width of the cutter.
The tool clearance angle must be perfectly regular.
To obtain a precise cutting width it is preferable to place the clearance angle at zero and release the tool holder at
360°.
- Move the cylinder so it lies tangent to the grinding wheel.
- Place the vernier at zero.
- Remove the necessary number of scales to obtain the chosen diameter, plus 1/10 to finish off.
- Make a trial cylinder.
Once you have obtained your chosen diameter, you then only need to indicate the clearance angle and grind your
cutter, not forgetting the 1/10.
- Position the grinder on T for Tip.
Regrinding 1/4 round cutters
In order to regrind a 1/4 round cutter :
The clearance angle should be equal to 30°.
The cutting angle should be equal to 35°.
Position the tool holder on Screw on the indexing rod, position 3.
Reposition your cutter with the orientation finger.
Bring the rod back into position, indexing 3.
Grind the tip to the desired width.
Take the precaution of firmly placing the flat end on the arm so you do not mistake it for the flat part of the 1/4 round
cutter.
CG30•60