Hand held device for measuring screw threads by the three-wire method

An improved measuring device for utilizing the three wire method of measuring pitch diameter and minor diameter of screw threads the device utilizing a micrometer having an anvil and an advancing spindle within the anvil, comprising:

• a plurality of at least three cylindrical wires, said wires having an outer cylindrical surface capable of contacting a midpoint of a flank of a screw thread between an outer edge and an inner edge of said screw thread,
• a means to hold said wires in vertical orientation during measurement to limit rotation and to position said wires for contact with said threads, said means including a pair of wire holders for engaging said respective three wires, and
• a means to limit a rotational movement of said holders from the application of rotational force against said wire holders for said wires, said means including an anvil engaging attachment engagable to the anvil of the micrometer, said anvil engaging attachment having a slot, the anvil of the micrometer being insertable within said slot, said slot of said anvil engaging attachment closely receiving said anvil, said anvil engaging attachment including a movement limiting means having a recess defined therein, each said wire holder movable within said recess and said recess providing a barrier limiting the movement of each said wire holder to the confines of said recess.