Manual Drive Train & Axles
Work Example 8

WorkKey Level: 3
NATEF Automotive Tasks: Background

(Universal problem for thread pitch)

(1) Based on the thread pitch gauge in the illustration and given the chart below, what bolt size should be ordered?

(2) What is the drill size for a 1/4×20 bolt?

(3) What is the decimal equivalent of 5/8?

(4) What is the outside diameter at screw of drill size F?

                       13 threads per inch

 

 

American National Screw Thread Pitches

COARSE STANDARD THREAD (N.C.)
Formerly U.S. Standard Thread

 

Bolt or Tap Size	Threads Per Inch	Outside Diameter at Screw	Drill Sizes	Decimal Equivalent of Drill
1	64	.073	53	0.0595
2	56	.086	50	0.0700
3	48	.099	47	0.0785
4	40	.112	43	0.0890
5	40	.125	38	0.1015
6	32	.138	36	0.1065
8	32	.164	29	0.1360
10	24	.190	25	0.1495
12	24	.216	16	0.1770
1/4	20	.250	7	0.2010
5/16	18	.3125	F	0.2570
3/8	16	.375	5/16	0.3125
7/16	14	.4375	U	0.3680
1/2	13	.500	27/64	0.4219
9/16	12	.5625	31/64	0.4843
5/8	11	.625	17/32	0.5312
3/4	10	.750	21/32	0.6562
7/8	9	.875	49/64	0.7656
1	8	1.000	7/8	0.8750
1 1/8	7	1.125	63/64	0.9843
1 1/4	7	1.250	1 7/64	1.1093

 

FINE STANDARD THREAD (N.F.)
Formerly S.A.E. Thread

Bolt or Tap Size	Threads Per Inch	Outside Diameter at Screw	Drill Sizes	Decimal Equivalent of Drill
0	80	.060	3/64	0.0469
1	72	.073	53	0.0595
2	64	.086	50	0.0700
3	56	.099	45	0.0820
4	48	.112	42	0.0935
5	44	.125	37	0.1040
6	40	.138	33	0.1130
8	36	.164	29	0.1360
10	32	.190	21	0.1590
12	28	.216	14	0.1820
1/4	28	.250	3	0.2130
5/16	24	.3125	I	0.2720
3/8	24	.375	Q	0.3320
7/17	20	.4375	25/64	0.3906
1/2	20	.500	29/64	0.4531
9/16	18	.5625	0.5062	0.5602
5/8	18	.625	0.5687	0.5687
3/4	16	.750	11/16	0.6875
7/¤8	14	.875	0.8020	0.8020
1	14	1.000	0.9274	0.9274
1 1/8	12	1.125	1 3/64	1.0468
1 1/4	12	1.250	1 11/64	1.1718

Solution:

(1) You need to order a 1/2" bolt x 13 tpi.

(2) 7

(3) 0.625

(4) 0.3125