ASME B1.16M-1984 pdf download
ASME B1.16M-1984 pdf download.Gages and Gaging for Metric M Screw Threads.
3 GENERAL PRACTICE
3.1 General Design
The design of gages is specified only to the extent that it affects the results obtained in the gaging of product threads. Moreover, to serve their intended purposes satisfactorily, thread gages should be produced by the latest and best manufacturing techniques. The type of steel or wear-resistant material selected, together with the heat-treating and stabilization processes, should provide wear life and dimensional stability. Thread gaging elements should be precisely manufactured to assure adequate refinement of surface texture, prevention or elimination of amorphous or smear metal, and uniformity of thread form over the entire length of the gaging member.
3.2 Types of Gages
GO thread gages check either the maximum- material limit or size to assure interchangeable assembly. HI and 10 thread gages inspect the HI and LO functional diameter limit.
GO and NOT GO plain cylindrical plug or ring gages and snap or indicating gages check the limit or size of the minor diameter of product internal threads and the major diameter of product external threads, respectively.
3.3 Interpretation of Tolerances
Tolerances on lead, half-angle, and pitch diameter are variations which may be taken independently for each of these elements and may be taken to the extent allowed by respective tabulated dimensional limits. The tabulated tolerance on any one element shall not be exceeded, even though variations in the other two elements are smaller than the respective tabulated tolerances.
3.4 Direction of Tolerances on Gages
At the maximum-material limit (GO), the dimensions of all gages used for final conformance gaging are to be within the limits of size of the product thread. At the functional diameter limit, using HI and 1.0 thread gages, the standard practice is to have the gage tolerance within the limits of size of the product thread. Specifications for gage limits are listed in Tables 4 and 5.
3.5 Standard Thread Gage Tolerances
Standard tolerances for thread-working gages, thread-setting plugs, and setting rings are as follows:
(a) W tolerances, shown in Table 7, represent the highest commercial grade of accuracy and work man- ship and are specified for thread-setting gages;
(b) X tolerances, shown in Table 6, are larger than W tolerances and are used for product inspection gages.
Unless otherwise specified, all thread gages and gaging contacts that directly check the product thread shall be X tolerance.
3.6 Tolerance on Lead
Cumulative effect of progressive or erratic helix variation and thick or thin end thread variations is specified as an allowable variation between any two threads not farther apart than the length of the standard taperlock or trilock gage, shown in ANSI/ ASME B47.laM. In the case of setting plugs, the specified tolerance shall be applicable to the thread length in the mating ring gage or nine pitches, whichever is smaller. For setting rings, the tolerance applies to a thread length of three pitches. The tolerance on lead establishes the width of a zone, measured parallel to the axis of the thread, within which the actual helical path must lie for the specified length of the thread. Measurements will be taken from a fixed referenc point located at the start of the first full thread to a sufficient number of positions along the entire helix to detect all types of lead variations. The amounts that these positions vary from their basic (theoretical) positions will be recorded with due respect to sign. The greatest variation in each direction [plus and minus (±)1 will be selected and the sum of their values, disregarding sign, shall not exceed the specified tolerance. If the variations are all in one direction, the maximum value governs conformance. In the case of truncated setting plugs, the lead variations present on the fullform portion and the truncated portion of an individual gage shall not differ from each other by more than 0.003 mm over any portion equivalent to the length of the thread ring gage, or nine pitches.
