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Drilling Holes |
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Amazingly, you can drill hardened stainless steel with a simple muscle powered bow drill or hand drill. The trick is not the drill but the bit. And you can make up your own bit. Get some coarse valve gringing paste from your local autoshop and a small wooden dowel or copper rod of a smaller diameter than that of your hole. Put the dowel in the drill, be it powered or not, and coat the tip in grinding paste then go at it for a day or so. Replenish the paste with fresh paste as soon as it feels like its not cutting. You can even cut through stone with a piece of stick and grinding paste and a bow drill or hand drill. But you need the patience of a Paleolithic hunter:-) |
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| There are three types of drilling machine in general use in the knife industry. | ||
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The Upright Drill Press. |
The Sensitive Drill Press. |
The Radial Drill Press. |
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Cutters used in the Drill Press |
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Twist Drills |
This is the most common form of drill tool and like the other cutters in this list an elaborate knife designed to cut and clear swarf from the work surface. Twist drills are used to make small to medium sized holes. A twist drill will tend to drill oversize so if accuracy is paramount the hole should be drilled undersize and finished to final size with a reamer. | |
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Spade Drills |
The spade drill can handle higher torques than the twist drill and can therefore be used to make larger holes. A spade drill will tend to drill oversize so if accuracy is paramount the hole should be drilled undersize and finished to final size with a reamer. | |
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Reamers |
The reamer is used to finish a hole to a particular size while imparting a smooth surface. Reamers are far more accurate than twist drills. | |
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Taps |
Taps are used to cut threads into a hole. | |
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Counterbores |
Counterbores are used to make a larger, square shouldered, bore at the opening to a hole in order to allow a bolthead to lie flush with the surface. | |
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Countersinks |
The Countersink makes a conical enlargement to the opening of a hole allowing a rivethead to be upset into the hole or a screwhead to lie flush with the surface. | |
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Spotfacers |
Spotfacers are used to finish the surface around the hole in order to ensure a level seat for a bolthead. | |
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Twist Drill Point Angles |
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| The harder the material the larger is the ideal point angle. Likewise softer materials drill better with an acute point angle. Plastic and wood, epoxy etc cut well at 60 degrees. Mild steel, annealed plain carbon steel, etc cut well at 120 degrees. Hardened tool steel, knife blades, etc require up to 150 degrees. |
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Twist drills cut oversize |
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1/16 |
Up to 2 thou oversize. | |
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1/8 |
Up to 4 thou oversize. | |
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1/4 |
Up to 6 thou oversize. | |
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1/2 |
Up to 8 thou oversize. | |
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3/4 |
Up to 8.5 thou oversize. | |
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1 |
Up to 9 thou oversize. | |
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Drill Bit alloys |
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| High Carbon Steel | ||
| High Speed Steel | ||
| Tungsten | ||
| Cobalt | ||
| Titanium Nitride | ||
