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REVERSE ENGINEERING
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ÀWỌN OHUN WÍWỌ̀

Forged Centre Punch, Hardened and Tempered
A centre punch marks the spot for a drill. It is forged from tool steel like a cold chisel: the point is tapered at a yellow heat and ground to an angle between 60° and 90°. Only the point is hardened: heat the end about 3 inches back, dip the point in water at about 70 °F (21 °C) while moving it, polish it, and let the heat left in the shank run down until the point turns brown or purple, about 500–525 °F (260–275 °C); then cool it completely. A good punch marks tool steel without its point going dull.
Àárín
1–2 hours
Ìlànà
1
1
Forge the taper
Forge the taper
Heat the end of the tool steel bar to a yellow heat and forge a long taper to a blunt point; finish just above the hardening heat, never hammering it black.
Àwọn ohun èlò fún ìgbésẹ̀ yìí:
Ọ̀pá onígun mẹ́jọ irin irinṣẹ́1 ẹyọÀwọn irinṣẹ́ tí a nílò:
Ìléru alágbẹ̀dẹ
Ìdí Alágbẹ̀dẹ
Òòlù Alágbẹ̀dẹ
Ẹmú Alágbẹ̀dẹ2
2
Cool and grind
Cool and grind
Let it cool slowly, then grind the point to an angle between 60° and 90°.
Àwọn irinṣẹ́ tí a nílò:
Òkúta ìfá oníkẹ̀kẹ́3
3
Harden the point
Harden the point
Reheat about 3 inches of the point end to the hardening heat, keeping the tip high in the fire. Dip the point into clean water at about 70 °F, moving it so no sharp line forms, then plunge briefly and lift out with heat left in the shank.
Àwọn irinṣẹ́ tí a nílò:
Ìléru alágbẹ̀dẹ
Bàkẹ́ẹ̀tì
Ẹmú Alágbẹ̀dẹ4
4
Temper
Temper
Polish the point quickly and watch the colours run down to it; when the point is brown or purple, cool the whole punch completely.
Àwọn irinṣẹ́ tí a nílò:
Aṣọ emery
Bàkẹ́ẹ̀tì5
5
Test
Test
Strike a mark in a piece of tool steel; the point should not dull.
Àwọn irinṣẹ́ tí a nílò:
Òòlù Alágbẹ̀dẹÀwọn ohun-èlò
1- Àyè
Ìtọ́nisọ́nà yìí ń ṣe
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