Abstract: A device for calibrating a drill bit of a chuck includes an intermediate sleeve including two rear curved elements, a front shoulder, internal threads rearward of the shoulder, and an externally threaded extension projecting out of a front end; a front window including a diametrical calibrating line; an externally threaded rim secured to the internal threads to urge the window against the shoulder; and a ring having internal threads secured to the extension. A fastening of the chuck and the device, a loosening of the retainer ring, and a rotation of the rear holding member to rotate the drill bit can align the drill bit with the calibrating line.

Abstract: A grinding machine of one embodiment includes an abrasive wheel; a rectangular base including a top wall having a central through hole and an upper shoulder; a mounting member secured to the central through hole; an electric motor including a drive shaft passing through the mounting member to secure to the abrasive wheel; first and third workpiece holding units each including a board secured to the base; an adjustment knob on the board; and an L-shaped seat secured to the board and having a transverse channel, a front curved slot, a rear projection pivotably secured to the board, and a pin secured to the board and disposed in the slot; a second workpiece holding unit secured to the shoulder and including a vertical tunnel; and a fourth workpiece holding unit secured to the shoulder and including a vertical tunnel, an adjustment knob, and a fastening member.

Abstract: A grinding machine of one embodiment includes an abrasive wheel; a rectangular base including a top wall having a central through hole and an upper shoulder; a mounting member secured to the central through hole; an electric motor including a drive shaft passing through the mounting member to secure to the abrasive wheel; first and third workpiece holding units each including a board secured to the base; an adjustment knob on the board; and an L-shaped seat secured to the board and having a transverse channel, a front curved slot, a rear projection pivotably secured to the board, and a pin secured to the board and disposed in the slot; a second workpiece holding unit secured to the shoulder and including a vertical tunnel; and a fourth workpiece holding unit secured to the shoulder and including a vertical tunnel, an adjustment knob, and a fastening member.

Abstract: A device includes a rear holding member including a front externally threaded projection and a varied-diameter passage; a flexible clamping member including a conic section, a rear tapered section, and an axial channel; a retainer ring including an inwardly extending annular member and an internally threaded section; a front holding member including a rear flange, a front conic passageway, and internal threads; and a fastening ring including rear threads, an internal shoulder, and two front, opposite curved members. The clamping member is urged against the passage; the retaining ring is put on the rear holding member; a drill bill is configured to insert through the channel into the passage; the front holding member has a rear end urging against the annular member; the internal threads are secured to the externally threaded projection, and an inner surface of the front holding member compresses the conic section.

Abstract: A device for calibrating a drill bill of a chuck includes an intermediate sleeve including two rear curved elements, a front shoulder, internal threads rearward of the shoulder, and an externally threaded extension projecting out of a front end; a front window including a diametrical calibrating line; an externally threaded rim secured to the internal threads to urge the window against the shoulder; and a ring having internal threads secured to the extension. A fastening of the chuck and the device, a loosening of the retainer ring, and a rotation of the rear holding member to rotate the drill bill can align the drill bill with the calibrating line.