ASME B1.16M-1984 pdf free download.Gages and Gaging for Metric M Screw Threads.
the product internal thread. In applying the thread snap limit gage, the HI functional diameter is acceptable when gaging elements do not pass the product thread.
Internal thread snap gages by design must have an outside diameter of gaging elements below minor diameter of internal thread in order to enter. The gage checks the HI functional diameter limit by sensing the resistance to contact after being set to master.
The HI thread snap gage will also indicate out-of- roundness of the pitch cylinder for 180 deg. ova lity by using the gage at different diametral locations on internal thread. The HI thread snap gage will also check for taper of pitch cylinder by using the gage at different locations axially on internal thread.
4.4.2 Basic Design. In order that the [II thread snap gage may effectively check the H I functional diameter limit, the flank contact is reduced by truncating the thread on segments and rolls. As the design of the segments and rolls is different with each gage manufacturer, the number of threads engaged in product thread will vary. Usually. the number of pitches engaged is approximately two. Internal product threads less than 5 mm in diameter are not practical to check with snap gages.
4.4.3 Thread Form. The specifications for thread form are summarized in Table 4 and Fig. 5.
4.4.4 Thread Crests. The maximum major diameter of the I-fl segments and rolls shall be equal to the pitch diameter of segment or roll plus O.2p with the gage tolerance minus. This corresponds to a width of flat at the crest equal to O.385p. See Table 4.
44.5 Thread Roots. The minor diameter of the I-Il segments and rolls shall be cleared beyond a p18 width of flat by an extension toward a sharp vee of the sides of the thread or by an undercut to any dimension no wider than p/4. Undercut is to be approximately central with the center line of the thread groove. See Fig. 5.
4.4.6 Runout. The pitch and major cylinders of the threaded portion of the H I segments or rolls shall not exceed the runout as determined by measurements of runout (full-indicator movement) on each gaging member, with respect to the pitch cylinder. Runout shall not exceed one-half of the X gage major diameter tolerance.
4.4.7 Pitch Cylinder. The pitch cylinder of the threaded portion of the HI segments or rolls shall be round within the X gage pitch diameter limits specified.
4.4.8 Lead, Pitch, and Half-Angle Variations. Lead, pitch, and half-angle variations shall be within the limits specified. See Table 6.
4.4.9 Identification. The assembled gage should be marked by the metric nominal size, pitch-tolerance class, HI, PD, and pitch diameter in millimeters.
EXAM P L. E:
M8 X P-6H HI PD7.500
4.5 Thread Snap Gages — Minimum
Material: Pitch Diameter Cone and Vee (Table 2 — Gage 2.5)
4.5.1 Purpose and Use. The thread snap gage with two segments or two rolls, both made to cone and vee design as shown in Fig. 6, inspects the minimum-material limit pitch diameter, C,, of the product internal thread.
Internal thread snap gages by design must have an outside diameter of gaging elements below minor diameter of internal thread in order to enter. The gage checks the minimum—material pitch diameter limit by sensing the resistance of contact after being set to master.
The cone and vee snap gage can check roundness of pitch cylinder for 180 deg. ovality by using the gage at different diametral locations on internal thread.
The cone and vee snap gage can check taper of pitch cylinder by using the gage at different locations axially on internal thread.
4.5.2 Basic Design. The segments are usually made having a surface contact slightly above the pitch line near the center of the flank. The rolls are made with a point or line contact approximately at the pitch line, depending upon the angle variations of the thread flanks. See Fig. 6 for details. Internal product threads less than 5 mm in diameter are not practical to check with snap gages.
4.5.3 Thread Form. The specifications for thread form, thread crests, and thread roots are summarized in Fig. 6.