Speed (strokes per minute) and feed pressure are the two factors that greatly determine power hacksaw blade performance.
As stroke rate and pressure are increased, blade life decreases, therefore it is important not to overwork the blade, creating excessive frictional heat and premature blade wear.
Because of vast differences between applications and materials, exact recommendations of feed pressures are impossible to determine. The conditions of the workpiece and the chips are the telltale factors. If vibration is severe, the feed pressure is excessive. If chips are blue or burned or tooth breakage occurs, again, feed pressure is excessive. Crooked cuts may also result.
Too many strokes per minute will prematurely dull the teeth because the teeth are rubbing, not cutting, creating high frictional heat. Powdery chips also indicate insufficient pressure, and probably too much speed.
A well curled chip, free of any color, is a sign the best combination of feed pressure and speed has been reached.
Correct tensioning of the blade is very critical. A loose blade will usually cut off, or cut crooked. Too much tension may elongate the pin holes severely and breakage could occur.
|CUTTING RECOMMENDATIONS – POWER HACKSAW BLADES|
|Type of Material||Number of Teeth per Inch||Strokes per Min.||Feed|
|Material 2″ and Under||Material Over 2″||Inches per Stroke||Pounds Pressure|
|Aluminum – Alloy||6||4||100-150||.003-.012||60|
|Brass – Free Machining||6-10||4-6||120-150||.003-.012||60|
|Brass – Hard||6-10||6||100-135||.003-.006||60|
|Brass – Tubing||10-14||10-14||120-150||.003-.006||60|
|Bronze – Commercial||6-10||4-6||90-120||.003-.006||120|
|Bronze – Manganese||6-10||6||60-90||.003-.006||60|
|High Density Alloys – A286||4||4||50-75||.006-.009||300-400|
|High Density Alloys – Discalloy||4||4||50-75||.006-.009||300-400|
|High Density Alloys – Hastelloy||4||4||50-75||.006-.009||300-400|
|High Density Alloys – Titanium||4||4||50-75||.006-.009||300-400|
|Iron – Cast||6-10||4-6||90-120||.009-.012||120|
|Iron – Malleable||6-10||6||90||.006-.009||125|
|Iron – Pipe||10-14||10-14||90-120||.003-.009||60-100|
|Nickel Alloy – Inconel||6-10||4-6||50-80||.003-.009||100-120|
|Nickel Alloy – Monel||6-10||4-6||60-90||.003-.009||100-150|
|Nickel Alloy – Nickel||6-10||4-6||60-90||.003-.009||100-150|
|Steel – Alloy||6-10||4-6||60-120||.003-.009||100-150|
|Steel – Carbon Tool||6-10||6||60-90||.003-.009||120|
|Steel – Cold Rolled||6||4-6||100-135||.006-.012||125|
|Steel – Hot Rolled||6||4-6||100-135||.006-.012||125|
|Steel – High Speed||6-10||6||60-90||.003-.006||120|
|Steel – Machinery||6-10||4-6||100-135||.006-.009||150|
|Steel – Pipe and Tubing||10-14||6-14||90-135||.006-.009||50-100|
|Steel – Stainless||6-10||4-6||60-90||.003-.009||100-150|
|Steel – Structural||6-10||6-10||90-135||.003-.006||120|
|Steel – Tool||6-10||6||60-90||.003-.009||120|
These figures are given as a guide and are approximate for machines in good mechanical condition. In cases where more than one tooth specification is given, select the proper blade on the the basis of the shape and size of the material. Use a blade with coarser teeth for cutting large, solid stock; a blade with finer teeth for cutting smaller stock.
Blades should be wide enough to withstand required pressure. . . 1″ and 1 1/4″ for light cutting (such as pipe or tubing) with short blades. . . 1 1/4″ to 2″ for heavy cutting with longer blades. It is important to use a cutting lubricant for all metals except cast iron.