Bolt

Bolt, commonly used with nuts, are the most widely used non-permanent fastening. The bolt head is usually hexagonal but may be square or round. The shank is screwed with a vee thread for all or parts of its length.

Materials

Most bolts are made of low or medium carbon steel by forging or machining and the threads are formed by cutting or rolling. Forged bolts are called black and machined bolts are called bright. They are also made in high tensile (HT bolts 8.8), alloy steel, stainless steel, brass and other metals.

  

             

TYPES OF BOLTS

1. Machine Bolt             4. Stove Bolt

2. Eye Bolt                       5. U bolt

3. Stud Bolt                      6. Carriage Bolt

TYPES OF SCREWS

1. Cap Screw

2. Machine Screw

3. Set Screw

4. Power Screw

THE AMERICAN NATIONAL SCREW THREAD

TYPES OF THREADS- 

1. UNC (Unified National Coarse Series) – is recommended for general use, where jar and vibration are not important factors, where dis-assembly of parts is frequent, and where tapped holes are in metals other than steel.

2. UNF (Unified National Fine Series) – is frequently used in automotive and aircraft work especially where jar and vibration (tending to loosen the nut) are present, where a fine adjustment is required with the use of a castle nut, and where a fine adjustment is required with the use of castle nut, and where tapped holes are in steel (avoid UNF in brittle materials)

3. UNEF (Unified National Extra Fine) – is particularly useful in aeronautical equipment, suitable where thin-walled materials is to be threaded, where fine adjustment are required, and where jar and vibration are excessive. Screws with these threads are likely to be made of heat treated alloy steel.

4. 8UN (Unified 8 – thread series) – is used on bolt for high-pressure pipe flanges, cylinder-head studs, etc. These are several constant pitch series, the 12 UN, 16 UN, and 20 UN. These threads are useful because in the regular coarse thread, the pitches continue to increase with size and it becomes increasingly difficult to induce the desire initial tension in the bolt, so necessary for tight joint. Even for the 8 UN thread, impact wrenches or very large leverages are needed for tightening to stresses of the order of the yield strengths. 

EXTRA FINE 8-THREAD SERIES TABLE

EXTRA FINE SERIES (NEF AND UNEF)					8-THREAD SERIES (8 N and 8 UN) (Primary Sizes)
Size	Basic Major Diameter, in.	Th./In. (tpi)	Minor Dia. Ext Th.	Stress Area AS sq. in.	Size	Minor Dia. Ext. Th.	Stress Area As sq. in
12	0.2160	32	0.1777	0.0270	1	0.8466	0.606
1/4	0.2500	32	0.2117	0.0379	1 1/8	0.9716	0.790
5/16	0.3125	32	0.2742	0.0625	1 ¼	1.0966	1.000
3/8	0.3750	32	0.3367	0.0932	1 3/8	1.2216	1.233
7/16	0.4375	28	0.3937	0.1274	1 1/2	1.3466	1.492
1/2	0.5000	28	0.4562	0.170	1 5/8	1.4716	1.78
9/16	0.5625	24	0.5114	0.214	1 3/4	1.5966	2.08
5/8	0.6250	24	0.5739	0.268	1 7/8	1.7216	2.41
11/16	0.6875	24	0.6364	0.329	2	1.8466	2.77
3/4	0.7500	20	0.6887	0.386	2 1/4	2.0966	3.56
13/16	0.8125	20	0.7512	0.458	2 1/2	2.3466	4.44
7/8	0.8750	20	0.8137	0.536	2 3/4	2.5966	5.43
15/16	0.9375	20	0.8762	0.620	3	2.8466	6.51
1	1.0000	20	0.9387	0.711	3 1/4	3.0966	7.6738
1 1/16	1.0625	18	0.9943	0.799	3 1/2	3.3466	8.96
1 1/8	1.1250	18	1.0568	0.901	3 3/4	3.5966	10.34
1 3/16	1.1875	18	1.1193	1.009	4	3.8466	11.81
1 1/4	1.2500	18	1.1818	1.123	4 1/4	4.0966	11.38
1 5/16	1.3125	18	1.2443	1.244	4 1/2	4.3466	15.1
1 3/8	1.3750	18	1.3068	1.370	4 3/4	4.5966	16.8
1 7/16	1.4375	18	1.3693	1.503	5	4.8466	18.7
1 1/2	1.5000	18	1.4318	1.64	5 1/4	5.0966	20.7
1 9/16	1.5625	18	1.4943	1.79	5 1/2	5.3466	22.7
1 5/8	1.6250	18	1.5568	1.94	5 3/4	5.5966	24.9
1 11/16	1.6875	18	1.6193	2.10	6	5.8466	27.1

HEX HEAD BOLT STANDARD DIMENSION (by American Society Of Mechanical Engineering)

Bolt Diameter	Body Diameter       Max                 Min		Across Flat	Across Corner         Max             Min		Height of Bolt	Length Tread 6 in. below	Length Tread 6 in. Above
¼	0.26	.237	7/16	.505	.484	11/64	.75	1.0
5/16	.324	.298	½	.577	.522	7/32	.88	1.13
3/8	.388	.360	9/16	.650	.62	¼	1.0	1.25
7/16	.452	.421	5/8	.722	.687	19/64	1.13	1.38
½	.515	.482	¾	.866	.826	11/32	1.25	1.50
5/8	.642	.605	15/16	1.083	1.033	27/64	1.50	1.75
¾	.768	.729	1 1/8	1.299	1.24	½	1.75	2.00
7/8	.895	.852	1 5/16	1.516	1.447	37.64	2.0	2.25
1	1.022	.976	1 ½	1.732	1.653	43/64	2.25	2.50
1 1/8	1.149	1.098	1 11/16	1.949	1.859	¾	2.50	2.75
1 ¼	1.277	1.223	1 7/8	2.165	2.066	27/32	2.75	3.00
1 3/8	1.404	1.345	2 1/16	1.949	1.859	29/32	3.00	3.25
1 ½	1.531	1.47	2 ¼	2.598	2.48	1	3.25	3.50
1 ¾	1.785	1.716	2 5/8	3.031	2.893	1 5/32	3.75	4.00
2	2.039	1.964	3	3.164	3.306	1 11/32	4.25	4.50
2 ¼	2.305	2.212	3 3/8	3.897	3.719	1 ½	4.75	5.00
2 ½	2.559	2.461	3 ¾	4.33	4.133	1 21/32	5.25	5.50
2 ¾	2.827	2.711	4 1/8	4.763	4.546	1 13/16	5.75	6.00
3	3.081	2.961	4 ½	5.196	4.959	2	6.25	6.50
3 ¼	3.335	3.21	4 7/8	5.629	5.372	2 3/16	6.75	7.0
3 ½	3.589	3.461	5 ¼	6.062	5.786	2 5/16	7.25	7.50
3 ¾	3.858	3.726	5 5/8	6.495	6.198	2 ½	7.75	8.00
4	4.111	3.975	6	6.928	6.612	2 11/16	8.25	8.50