LA TARIFFA
La “tariffa” era un’incisione fatta con “sciubbia” e “mazzolo”, simile alla “formella” ma più stretta, meno profonda e lunga quanto la parte da eliminare.
Ultimata quest’incisione, si facevano internamente dei piccoli fori alla distanza di 5-7 cm l’uno dall’altro ed in essi si continuava a battere puntando la “sciubbia” in posizione perpendicolare, per più passaggi, finché si generavano delle sfaldature interne e la “tariffa” si sollevava staccando la parte da scartare.

http://dallascuola.direscuola.it/giornale_studenti/anno/2011...

Broaching.— In granite and other hard stones holes must be placed closer together and, as a rule, splitting across the grain is abandoned in favor of broaching. In this system, a series of holes is drilled, usually about three inches apart from centre to centre, leaving walls of three-quarters inch to two inches between, de pending upon the hardness of the rock, and a flat bit or Is subotituted for the regular steel. This has a face about three inches by three-quarters inch thick and is forged with a blunt end to crush this wall or web between the holes. Drills used for broaching must have the release which is a simple device to throw the pawls out of action and allow the drill to work without rotating. Broach channeling is the best and cheapest method of cutting out key blocks, lumps, and making wall cuts, etc., in granite quarries, where the rock is too hard to be cut advantageously with the regular channel ing machine.

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