Drilling Steel (continued)

---

Complete Reconditioning

Here is a description of a modern tool reconditioning process:

Forging

1. Heat the point to a yellow color (1800 to 1900ºF/982 to 1038ºC), for the length necessary to forge. Be careful not to heat too far back on the steel; this is the most common cause of premature breaking after reconditioning. Do not attempt to forge below a cherry red color, (1450ºF/790ºC) (see Incandescent Colors and Temperatures chart).

2. Rework tools only to their original design.

3. After forging allow the tool to cool to room temperature.

Hardening

1. Reheat the point to a cherry red color 1 1/2 to 2 inches back from the cutting edge, making sure to overlap the forging depth

Quenching

1. 1. Quench in water, or in a brine or oil solution. Maintain the quench at a temperature of 75 to 100ºF/24 to 38ºC, to achieve Rockwell hardness (Rc) 60 to 65, Brinell hardness (HB) 600 to 652

Tempering

1. Withdraw the tool from the quench with sufficient heat remaining in it to draw the temper. A shade of brown or dark yellow is best.

2. Rub the point clean with emery.

3. When a light straw color appears, (430ºF/222ºC), complete the quench.

4. If drawing facilities are available, reheat to 425ºF/ 218ºC, and hold for 1 hour to achieve Rc 56 to 60, H B 555 to 600.

Miscellaneous Tips

1. Temperatures will vary among types of tool steel.

2. This operation should be undertaken only by or under the close supervision of an experienced blacksmith who knows the specific requirements of the steel he uses.

3. Wear adequate protective clothing, including eye protection and gloves, at all times.

If your drilling steel includes short 'starters' and longer 'seconds', the smith should make the cutting bits diminish slightly in width as the rods increase in length. This is necessary to prevent jamming when a new length of steel is started in the hole. A drilled hole gradually decreases in diameter as the tool wears. The bore-hole is not a true cylinder, but the frustum of an elongated cone. If the head of the steel becomes mushroomed from extended use, it should be reshaped by the blacksmith during reconditioning.

The bore-hole is not a true cylinder,
but the frustum of an elongated cone.

Defective Steel and Prolonged Safe Use

Although drilling steel is designed to perform in demanding applications, few products are subjected to more stress in service. Hand-hammered percussion tools for drilling and wedging must endure the same punishment as the rock being worked, so some failures may be expected.

Defective steel is likely to fail early on due to the severe stresses from the blows of the hammer, although some break after considerable service without having been defective. To insure long life and safe use of drilling steel, avoid these common causes of premature failure:

1. Using steel for an unintended purpose. Prying with the steel, for example, will bend it and render it unsafe and ineffective.

2. Allowing steel to overheat in service. This will draw temper and cause cutting edges to soften and dull.

3. Failing to keep the steel sharp. This causes extra stress on the rod.

4. Redressing steel inadequately or improperly. Tools improperly forged and rehardened or excessively filed will dull quickly, mushroom prematurely, and break before giving a full measure of service.