ASME B1.13M-2001 pdf download
ASME B1.13M-2001 pdf download.METRIC SCREW THREADS: M PROFILE.
5.5.2 Internal Thread Tolerance Class. No allowance (fundamental deviation). Tolerance class 6H6H. Internal threads with allowance are not standard practice.
5.6 Length of Thread Engagement
5.6.1 Normal Length of Thread Engagement.
The pitch diameter tolerances specified herein are applicable to the limits of the normal length of thread engagement LE in Table 7. The limits were calculated by formulas given in para. 6.4.
5.6.2 Short and Long Lengths of Thread Engagement When Gaged With Normal Length Contacts. For short LE length of thread engagement, reduce the pitch diameter tolerance of the external thread by one tolerance grade number. For long LE length of thread engagement, increase the allowance (fundamental deviation) at the pitch diameter of the external thread. For internal threads with long LE length of thread engagement, provide an allowance (fundamental deviation) corresponding to the next larger tolerance position. Thus, for the standard H position (no allowance), a tolerance position G would be provided. For assemblies with short or long lengths of engagement, the tolerance class adjustment may be applied to only one member. See Table 8.
5.7 Circular Runout
Circular runout is the full indicator movement (FIM) (see ASME Y14.5). Runout of the crest (minor diameter of internal thread or major diameter of external thread) relative to the pitch cylinder shall not be so great that the basic profile is transgressed.
5.7.1 Internal Thread. When measurement is specified, the runout of the minor diameter cylinder relative to the pitch cylinder on the internal thread shall not exceed the difference between the measured minor diameter and the basic minor diameter. An out-of-round pitch cylinder may reduce the available runout.
5.7.2 External Thread. When measurement is specified, the runout of the major diameter cylinder relative to the pitch cylinder on the external thread shall not exceed the difference between the measured major diameter and the basic major diameter. An out- of-round pitch cylinder may reduce the available runout.
5.8 Lead and Flank Angle Tolerances
8.2 Material limits for Coated Threads
Unless otherwise specified, size limits for standard external thread tolerance classes 6g and 4g6g apply prior to coating. The external thread allowance may thus be used to accommodate the coating thickness on coated parts, provided that the maximum coating thickness is no more than 1/4 of the allowance. Thus, a 6g thread after coating is subject to acceptance using a basic size 6h GO thread gage and a 4g6g thread, a 4h6h GO thread gage. (Basic thread sizes, tolerance position h, are tabulated in Nonrnandatory Appendix D.) Minimum material, LO or NOT.GO gages would be 6g and 4g6g, respectively. Where external thread has no allowance or allowance must be maintained after coating, and for standard internal threads, sufficient allowance must be provided prior to coating to assure that finished product threads do not exceed the maximum material limits specified. For thread classes with tolerance position H or h, coating allowances in accordance with Table 13 for positions G or g respectively, should be applied whenever possible. See paras. 8.4, 8.5, and 8.6.
8.3 Dimensional Effects of Coating
(a) On a cylindrical surface, the effect of coating is to change the diameter by twice the coating thickness — one coating thickness on each side of the cylinder. Because the coating thickness is measured perpendicular to the coated surface, while the pitch diameter is measured perpendicular to the thread axis, the effect of a uniformly coated thread flank on the pitch diameter is a change four times the thickness of coating on the flank. See Fig. 6. The diameters of external threads before coating will be smaller while the diameters of internal threads before coating will be larger than the coated diameters.
(b) Most coatings and platings do not apply uniformly on threads (see Fig. 7). Different coating materials and processes have different application characteristics. The threaded part’s overall length and other configuration characteristics also affect the way coatings build up on the threads. Paragraphs 8.4, 8.5, and 8.6 provide general guidelines for calculating pre-coating thread size to allow for coating build-up while preventing interference in assembly. The exact precoating thread size for a given part with a given type of coating will frequently have to be developed by the producer experimentally.
