This invention, a thread chase with a lead that acts as a smooth bore guide into a threaded hole is suitable where space is confined, and the male thread chase must be exactly aligned with the female threads, “sight unseen”, or damage to female threads may result by applying force to a misaligned thread chase, particularly where the female threads are of softer metals. The lead smooth bore also prevents shavings and other debris resulting from the cleaning from the chase, from falling into the hole that is being cleaned. A recessed tapered area between the threaded portion of this case and the lead smooth bore guide collects the shavings or cleaning residue so that when the tool is withdrawn from the hole, the shavings and cleaning residual will collect in that area and not fall into the threaded hole being cleaned.

A method of configuring a machine (201) for production of a thread, having a pitch (227), on a workpiece (310), the machine (201) comprising: a tool (220) having a thread (223) centred on a first axis (250) and comprising one or more thread-producing peaks (225) for producing the thread having the pitch (227); and a tool holder (210) holding the tool (220), the method comprising: determining a first distance (441), in a first direction (260) parallel to the first axis (250), from a reference position (412) of the tool holder (210) to a first thread-producing peak (226) on the tool (220) when said tool (220) is held in the tool holder (210); and setting a first configuration (401) of the machine (201) wherein the reference position (412) of the tool holder (210) has a displacement (440) parallel to the first axis (250) from a reference position (411) of the workpiece (310) depending only upon: the determined first distance (441); a translation (443) parallel to the first axis (250) to account for an angular offset (340) between the first thread-producing peak (226) and a desired thread start position (311) on the workpiece (310); and an integer multiple (444) of the pitch (227).

A method of configuring a machine (201) for production of a thread, having a pitch (227), on a workpiece (310), the machine (201) comprising: a tool (220) having a thread (223) centred on a first axis (250) and comprising one or more thread-producing peaks (225) for producing the thread having the pitch (227); and a tool holder (210) holding the tool (220), the method comprising: determining a first distance (441), in a first direction (260) parallel to the first axis (250), from a reference position (412) of the tool holder (210) to a first thread-producing peak (226) on the tool (220) when said tool (220) is held in the tool holder (210); and setting a first configuration (401) of the machine (201) wherein the reference position (412) of the tool holder (210) has a displacement (440) parallel to the first axis (250) from a reference position (411) of the workpiece (310) depending only upon: the determined first distance (441); a translation (443) parallel to the first axis (250) to account for an angular offset (340) between the first thread-producing peak (226) and a desired thread start position (311) on the workpiece (310); and an integer multiple (444) of the pitch (227).

A method of producing a rotationally orientated thread starting at a desired angular position and suitable for mass production is provided. The method is particularly suitable for improving the angular positioning of spark plugs in car engines. The method involves measuring precisely the length (L) of the tool (13) and the distance, at a particular angular position, of a full thread form (14) of the thread to the tip, so that its start position at the tip can be calculated. Using that distance as an offset of the length of the tool reported to the CNC machine, and starting from its reference position, it commences producing the thread (12) in the bore (11) at the desired angular position of the bore (11).