ALESOIR EXPANSIBLE

LE POUSSOIR 24, ENTRAINE PAR LA BROCHE S, ENTRAINE A SON TOUR LE CORPS 10 PAR LE GOUJON 34 ET LA FENTE 22. 10 PORTE EN BOUT LE PIVOT 38 DES LAMES DE COUPE 40. QUAND ON REPOUSSE 24, LES MANCHONS 64 ET 60 AVEC LA BUTEE A BILLES 62 ASSURENT L'APPUI DE 10 CONTRE LA PAROI, TANDIS QUE LE GOUJON D'ETRIER 50 PREVU EN BOUT DE 24 COULISSE DANS LES RAINURES 48 DES LAMES 40 QU'IL ECARTE POUR CHAMBRER LE TROU.APPLICATION AU CHAMBRAGE CONIQUE DE TROUS PERCES DANS DU BETON POUR RECEVOIR DES TIRANTS D'ANCRAGE A TETE EXPANSIBLE. A rotary expansion tool for undercutting walls of a pre-existing cylindrical hole in which it is a snug fit, the tool having a hollow shaft with opposed longitudinal slots through its sides near its inner end; a push rod extending from a tool-drive coupling at the outer end of the shaft, non-rotatably into the shaft and terminating at a clevis near the opposed slots; the tool having cutter means attached by a pivot pin to the shaft and pivotable about the pin so that the cutter means can extend one of its longitudinal edges transversely outwardly through one slot to contact the walls of the hole, and can extend its opposite longitudinal edge into the other slot to stabilize the cutter; the clevis surrounding the cutter means and cooperating with diagonal slots therein to rotate the cutter means outwardly of the tool when the push rod is urged axially inwardly of the tool; and means for locating the position in the hole of the undercut with reference to the mouth of the hole.