US 7,490,411 B2
Screw measuring method, screw measuring probe, and screw measuring apparatus using the screw measuring probe
Sadayuki Matsumiya, Kawasaki (Japan); and Masanori Arai, Kawasaki (Japan)
Assigned to Mitutoyo Corporation, Kanagawa (Japan)
Filed on Mar. 01, 2007, as Appl. No. 11/712,491.
Claims priority of application No. 2006-072862 (JP), filed on Mar. 16, 2006.
Prior Publication US 2007/0240318 A1, Oct. 18, 2007
Int. Cl. G01B 5/08 (2006.01); G01B 5/20 (2006.01)
U.S. Cl. 33—199R  [33/504] 10 Claims
OG exemplary drawing
 
1. A screw measuring method comprising:
an internal-dimension measuring step of using a coordinate measuring machine provided with a screw measuring probe that has a stylus-tip sphere having a diameter selected according to the pitch of a female screw to measure internal-dimension information Dw equal to the diameter of a cylinder having a center axial line identical with the axial line of the female screw and having a wall that passes through the center of the stylus-tip sphere when the stylus-tip sphere is butted against the screw groove of the female screw, based on coordinate information measured while the stylus-tip sphere is butted against the screw groove of the female screw; and
an effective-diameter calculating step of obtaining effective-diameter information De of the female screw from the internal-dimension information Dw measured in the internal-dimension measuring step, diameter information 2r of the stylus-tip sphere, and thread angle information α and pitch information P of the female screw, by using an effective-diameter calculation expression De=Dw+2r×cosec(α/2)−(P/2)×cot(α/2).