Sect. 131 page 175, sous le titre "Example of tubular drilling" vous y trouverez ceci:
Si vous ne comprenez pas l'anglais, vous pouvez passer par google traduction. Vous pourrez y lire, entre autre:131. Next the Egyptians adapted their sawing principle into a circular,
instead of a rectilinear form, curving the blade round into a tube, vrhfch drilled
out a circular groove by its rotation ; thus, by breaking away the cores left in
the middle of such grooves, they were able to hollow out large holes with a
minimum of labour. These tubular drills vary from \ inch to 5 inches diameter,
and from ^ to 4^ inch tliick. The smallest hole yet found in granite is 2 inches
diameter, all the lesser holes being in limestone or alabaster, which was probably
worked merely with tube and sand. A peculiar feature of these cores is that
they are always tapered, and the holes are always enlarged towards the top.
In the soft stones cut merely with loose powder, such a result would naturally
be produced simply by the dead weight on the drill head, which forced it into
the stone, not being truly balanced, and so always pulling the drill over to one
side ; as it rotated this would grind off material from both the core and the
hole. But in the granite core. No. 7, such an explanation is insumdent, since
the deep cutting grooves are scored out quite as strongly in the tapered end
as elsewhere ; and if the taper was merely produced by rubbing of powder, they
would have been polished away, and certainly could not be equally deep in
quartz as in felspar. Hence we are driven to the conclusion that aoxiliaiy
cutting points were inserted along the side, as well as around the edge of the
tube drill ; as no granite or diorite cores are known under two inches diameter,
there would be no impossibility in setting such stones, working either through
a hole in the opposite side of the drill, or by setting a stone in a hole cut
through the drill, and leaving it to project both inside and outside the tube.
Then a preponderance of the top weight to any side would tilt the drill so as to
wear down the groove wider and wider, and thus enable the drill and the dust
to be the more easily withdrawn from the groove. The examples of tube
drilling on PL xiv, are as follow : — No. 7, core in granite, found at Gizeh.
No. 8, section of cast of a pivot hole in a lintel of the granite temple at Gizeh;
here the core, being of tough hornblende, could not be entirely broken out, and
remains to a length of '8 inch. Na 9, alabaster mortar, broken in course of
Le plus petit trou encore trouvé dans le granit est de 2 pouces diamètre, tous les trous inférieurs étant en calcaire ou en albâtre, ce qui était probablement travaillé uniquement avec le tube et le sable. Une caractéristique particulière de ces noyaux est que ils sont toujours conique, et les trous sont toujours agrandi vers le haut.
Une meilleure traduction serait la bienvenue, mais malgré le titre "Example of tubular drilling" il fait bien référence à des carottages coniques.Mais dans le cœur de granit. N ° 7, une telle explication est insumdent, depuis les gorges profondes de coupe sont notés sur un peu moins vigoureux dans l'extrémité conique comme ailleurs