Antikythera Fragment #5 - Ancient Tool Technology - The First Precision Drill Bit

Antikythera Fragment #5 - Ancient Tool Technology - The First Precision Drill Bit, by Clickspring.

There are a number of cutting tools implied in the wreckage of the Antikythera Mechanism, and one of the most interesting is the drill bit. In this video I explore a possible method of how an effective and precise drill bit could have been made in antiquity.

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Abbreviated Transcript:

00:12 The existence of an Ancient style of drill bit is strongly implied in the wreckage of the Antikythera Mechanism. And its fabrication would have likely hinged on a crucial process: The ability to take a malleable wrought iron, and transform it into something hard enough to cut bronze.
00:28 I've covered the process in detail in a separate video, but essentially it involves packing an animal based charcoal and salt around the soft iron, sealing it in clay, and then heating it up to a red heat I'm using a low carbon mild steel as a substitute for Ancient wrought iron. Its soft and ductile.
01:00 But there are some great examples of long slender turning to be found within the wreckage of the mechanism itself. There's a shaft that extended from the lunar phase gearing up to the phase display on the front dial that's roughly 4mm in diameter.
01:16 And there are numerous other pins and shafts, some less than a mm in diameter. I'm using a modern furnace for convenience, but a traditional charcoal furnace is quite capable of generating the required temperature. Once at a red heat, the process of carburising the iron is purely a time exercise.
01:51 So I reheated the rods, rolled them straight on a flat surface, and then requenched. The once soft metal is now very hard, but also extremely brittle, and so easily fractures under a light bending load. So to be of use as a cutting tool, it needs to be tempered, in this case to a light straw color.
02:40 I can see this end of the rod is a good straight section, so that'll become the actual bit, and the excess will be removed at the end of the process. A gentle heat raises the temperature of the rod until a pale straw color just reaches what will become the cutting end. The material is now in a tempered state. Still very hard, but tough rather than brittle.
03:23 Despite no longer being widely used, it still has a number of attributes to recommend it. The first being that its very easy to make. Because the primary surfaces can all be formed by hand, on flat abrasive stones. The cutting edges can be shaped for unidirectional cutting, or as in the case that I'm showing onscreen, for single direction cutting.
03:59 And once the operational length has been decided, it can be permanently set by scoring the metal with a file, and then snapping off the excess material.
04:38 In its rigid cross section form, this sort of drill bit will often perform much like a traditional D bit. Delivering a very straight deep hole. Now there is of course an obvious drawback to the drill bit design: The need to repeatedly withdraw it from the work to clear the chips.
05:36 As soon as the cutting edges start to dull, a quick hit on the stones will bring them back to original condition. Now you won't want to throw out your twist drills any time soon, but its a great option to keep in mind for those rare occasions when you really do need a custom drill bit.

References:

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Antikythera Fragment #5 - The First Precision Drill Bit, by Clickspring.

Видео Antikythera Fragment #5 - Ancient Tool Technology - The First Precision Drill Bit канала Clickspring