Question 65

The Correct Answer is C ### Why Option C (blade from overheating) is Correct: When cutting metal using a power hacksaw (or any sawing method), friction is generated between the blade teeth and the workpiece. This friction produces significant heat. If the heat is not dissipated, the cutting edge of the blade will rapidly reach high temperatures, causing the teeth to lose their hardness (temper) and dull very quickly. A coolant (often a cutting fluid or soluble oil mix) is applied specifically to absorb this heat and carry it away, ensuring the blade maintains its operational hardness and extends its useful life. ### Why Other Options Are Incorrect: * **A) blade from bending:** While excessive force can cause a blade to bend, the primary function of the coolant is thermal management, not structural support. Proper tensioning and feed rate prevent bending. * **B) blade from catching on the work piece:** The geometry of the blade teeth (set and rake angle) and the proper securing of the workpiece prevent the blade from catching. Coolant does not affect this mechanical interaction directly, although lubrication can reduce friction. * **D) cut from clogging:** Coolants often help flush swarf (metal chips) away from the cut, which does prevent clogging, but this is a secondary benefit. The primary and most critical reason for using coolant is to manage the extreme temperatures generated by friction to preserve the tool's sharpness and temper.