3BG Class-of-Fit (obsolete)

MIL-STD-8879C (obsolete) contained paragraph 6.3 which is titled: Class 3BG.

MIL-STD-8879C: 6.3 Class 3BG
According to MIL-S-8879C paragraph 6.3 Class 3BG states: Class 3BG for high temperature applications shall no longer be used in new designs. This special class-of-fit for internal threads provides an allowance to both the GO and NOGO work plug gage pitch diameters of +0.0030" for 32-TPI and coarser. For finer ptch threads (finer than 32-TPI) +0.0010".

The above paragraph was not carried over to ANSI/ASME SAE AS8879. Also, 3BG is not mentioned at all in ANSI/ASME SAE AS8879.

MIL-STD-8879C (obsolete)
MIL-STD-8879C (obsolete)
UNJF Class 3BG only applies to internal threads
THREAD SIZE	MINOR DIAMETER		PITCH DIAMETER		MAJOR DIAMETER
THREAD SIZE	MIN	MAX	MIN	MAX	MIN
#0-80 UNJF-3BG	0.0489	0.0521	0.0529	0.0546	0.0610
#1-72 UNJF-3BG	0.0605	0.0641	0.0650	0.0669	0.0740
#2-64 UNJF-3BG	0.0718	0.0759	0.0769	0.0789	0.0870
#3-56 UNJF-3BG	0.0826	0.0872	0.0884	0.0905	0.1000
#4-48 UNJF-3BG	0.0927	0.0981	0.0995	0.1018	0.1130
#5-44 UNJF-3BG	0.1039	0.1098	0.1112	0.1136	0.1260
#6-40 UNJF-3BG	0.1147	0.1212	0.1228	0.1253	0.1390
#8-36 UNJF-3BG	0.1380	0.1452	0.1470	0.1497	0.1650
#10-32 UNJF-3BG	0.1626	0.1705	0.1727	0.1756	0.1930
#12-28 UNJF-3BG	0.1842	0.1926	0.1958	0.1989	0.2190
1/4"-28 UNJF-3BG	0.2182	0.2259	0.2298	0.2330	0.2530
5/16"-24 UNJF-3BG	0.2749	0.2829	0.2884	0.2920	0.3155
3/8"-24 UNJF-3BG	0.3374	0.3447	0.3509	0.3546	0.3780
7/16"-20 UNJF-3BG	0.3918	0.4000	0.4080	0.4121	0.4405
1/2"-20 UNJF-3BG	0.4543	0.4621	0.4703	0.4747	0.5030
9/16"-18 UNJF-3BG	0.5114	0.5196	0.5294	0.5338	0.5655
5/8"-18 UNJF-3BG	0.5739	0.5818	0.5919	0.5964	0.6280
3/4"-16 UNJF-3BG	0.6922	0.7007	0.7124	0.7173	0.7530
7/8'-14 UNJF-3BG	0.8085	0.8182	0.8316	0.8369	0.8780
1"-12 UNJF-3BG	0.9219	0.9319	0.9489	0.9546	1.0030
1-1/8"-12 UNJF-3BG	1.0469	1.0569	1.0739	1.0798	1.1280
1-1/4"-12 UNJF-3BG	1.1719	1.1819	1.1989	1.2049	1.2530
1-3/8"-12 UNJF-3BG	1.2969	1.3089	1.3239	1.3300	1.3780
1-1/2"-12 UNJF-3BG	1.4219	1.4319	1.4489	1.4552	1.5030

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Comments:
Original Posting: 11/13/2012
Last Revision: 12/20/2017
Error corrections in, or comments about, the above data can be sent to: office@gagecrib.com

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