Bow drill
A bow drill is a simple hand-operated type of
The spindle can be held into a fixed frame, or by a hand-held block (the hand piece or thimble) with a hole into which the top of the shaft is inserted. Some lubricant should be used to reduce friction between these two parts, otherwise, it could lead to some trouble when doing it too fast. A popular campcraft book of 1920 attributed this invention to the Inuit.[4] In Mehrgarh (Pakistan) it has been dated between the 4th-5th millennium BCE.[5]
The string of the bow is wrapped once around the spindle, so that it is tight enough not to slip during operation. In the variation called the Egyptian bow drill, the cord is wound around the shaft multiple times, or is fixed to it by a knot or a hole.[citation needed]
The strap drill is a simpler version, where the bow is absent and the cord is kept taut by pulling the ends with both of our hands, while moving them left and right at the same time. In the absence of a frame, the thimble is shaped so that it can be held with the chin or the mouth.[citation needed]
The bow lathe used for traditional woodturning uses the same principle as the bow drill.
History
Bow drills with
Usage as a fire drill
For use as a fire drill, the shaft should have a blunt end, which is placed into a small cavity of a stationary piece of wood (the fireboard). Turning the shaft with high speed and downward pressure generates heat, which eventually creates powdered charcoal and ignites it forming a small ember.[4]
For drilling, the lower end of the spindle may be fitted with a hard drill bit that creates the hole by abrasion or cutting.[citation needed]
See also
References
- ISBN 978-1-58218-748-8.
- ISBN 978-0-300-10341-0.
- ISBN 978-93-5025-939-9.
- ^ ISBN 978-0-486-80079-0.
- ISBN 0415329205.
- ISBN 0-415-32920-5.