Method of operating high speed electric arc saw

A method for cutting a kerf in a metal object with an electric arc saw including a saw blade and a means for adjusting the cutting depth of the blade in the metal object, said method comprising:

• advancing the saw blade in a first direction into close proximity with the object;
• passing a cutting current I between the saw blade and the object which equals at least:
• a.multidot.s.multidot.10.sup.6 amps wherein
• a is in the range of between about 2 and about 16;
• s is the effective surface area of the cut (arc segment length.times.kerf width) in m.sup.2 ;
• so that cutting of the object through melting of the metal commences substantially instantaneously upon the commencement of current flow between the member and the object;
• returning the saw blade opposite to the first direction through the kerf so that debris formed during the cutting stroke is removed therefrom;
• moving the blade to increase its cutting depth after completion of the returning step;
• and
• repeating the adjusting, returning and moving steps until the kerf extends to the desired depth in the object.

A method for cutting a kerf of a desired depth into a metal object with a relatively thin disc, the method comprising:

• (a) applying a voltage differential to the object and the disc;
• (b) rotating the disc;
• (c) advancing the disc from a starting position through the object and at a preselected depth so that the disc forms a cut having an arc segment 1 which is less than
• (I/w (j.sub.o +Mv))
• where:
• I=electric cutting current flowing between the disc and the object;
• J.sub.o =a.multidot.10.sup.6 amps/m.sup.2 ;
• a=a number in the range of 2 to 16;
• w=width of the kerf in m;
• v=desired cutting speed (m/sec.);
• M=(.DELTA.J/.DELTA.v);
• and
• J=incremental increase in the current density corresponding to an incremental increase v in the travel speed of the blade through the object;
• (d) returning the disc to the starting position;
• and
• (e) repeating steps (c) and (d) until the kerf is the desired depth.

A method for arc sawing a kerf in a metal object comprising:

• providing a relatively thin, circular disc;
• positioning the object at a cutting location;
• applying a preselected voltage across the object and the disc;
• moving the disc into a sufficiently close proximity with the object to initiate an electric current flow between the disc and the object;
• determining an optimum depth and cutting speed at which the disc can melt a cut in the object at the preselected voltage;
• advancing the disc in a first direction relative to the object and adjusting the relative depth and cutting speed of the disc to the optimum values so that the current melts a cut of a predetermined depth in the object;
• returning the disc through the cut in the opposite direction at substantially the same depth relative to the object;
• and
• repeating both the advancing and returning steps at increasingly greater relative depths until the kerf has been completed.