Lincoln Electric SP20/MP2 Series Safety Instruction For Use And Maintenance page 13

8695 9001 / E
Any black or blue-coloured marks indicate a post-gas fault.
POINTING
Pointing must be done using a grinding wheel, it is preferable not to hold the
electrode manually.
Ensure that the particles are removed along the generating lines of the cone whose
vertex angle must be 20 to 25%. This reduces erosion of the tungsten.
We also recommend terminating the grinding using a fine grain abrasive since the
resistance of the electrode in service is favoured when the surface finish of the
emissive part is carefully prepared.
The tip of the electrode point, which is vulnerable when striking the arc,must be
carefully eliminated by rubbing the point on a sheet of very fine grade abrasive.
Ensure that the grinding wheel is not a multi-purpose one since contaminant
particles could be deposited on the electrode.
To eliminate a deformed or contaminated point before pointing, or to cut a 150mm
electrode, never clamp the electrode in pliers or a vice, and never hit it with a hammer
to break the electrode or snap off the piece to be eliminated.
This type of operation risks creating micro cracks at the grain joints, or more simply
a deformation of the electrode structure which can cause cracks at high temperature;
cracks which will reduce the life of the electrode or cause plasma jet deviation.
SP20/SP45 - MP2/MP5
To shorten an electrode, we recommend that you notch the
electrode using the grinding wheel.
Use only straight electrodes with points concentric to the orifice
of the constricting nozzle to obtain a deviation-free plasma jet.
F - USING SP20/45 AND MP2/5 TORCHES
F-9