DIFFERENCE BETWEEN BOLT AND SCREW

In this article we will learn about the difference between bolt and screw. Almost in every parts that we see around us, whether it is your laptop, mobile, car, motorcycle and a giant machine like aeroplane, tanks, rockets etc. all are made by bolts and screws. We all are familiar with the bolts and screws, we have also used them in our daily life but we don’t know the exact difference between them. So let's learn about the differences.

Difference Between Bolt and Screw

S.no.	Bolt	Screw
1.	A bolt is an externally threaded fastener designed for insertion through holes in assembled parts, and is normally intended to be tightened or released by torquing a nut.	A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread, and of being tightened or released by torquing the head.
2.	The bolts have generally uniform cross section.	The screws generally have non uniform cross section.
3.	The bolts are always used with the nuts.	It is not used with the nuts but used alone.
4.	The threads on the bolts are spiral in structure.	The threads on the screw are helical in structure.
5.	It does not have tapered shank.	It has  tapered or pointed  shank.
6.	Bolts mostly requires wrenches and spanners for the tightening and loosening purposes.	The screw requires mostly screw drivers for the tightening and loosening purposes.
7.	The parts that are joined together with bolts have greater strength than screw	The parts joined together with the screw have less strength than bolt.
8.	It is more reliable.	It is less reliable.
9.	They apply compression on the parts that they join.	They don’t apply compression on the parts that they join.
10.	The parts that are to be joined with the bolts must have holes for its insertion.	Holes may or may not be required in the parts which are to be joined with the screws. In most of the cases it is directly screwed into the parts to be joined.
11.	The bolts are found in smaller as well as in large sizes.	The screw sizes are smaller or medium. They are not found in much larger sizes.
12.	The examples of bolts are: Anchor bolt, Carriage bolt, Elevator bolt, Flange bolt, Hanger bolt, Hexagon bolt/Tap bolt, Lag bolt, Machine bolt, Plow bolt, Sex bolt, Shoulder bolt, Square head bolt, Stud bolt, Timber bolt, T-head bolt, Toggle bolt, U-bolt, J-bolt, Eye bolts etc.	The examples of screws are: Wood screw, machine screw, thread cutting machine screw, sheet metal screw, self drilling sms, socket screw, eye lag, mating screw, set screw etc.

Summary of Difference Between Bolt and Screw

• The bolt is an external threaded fastener designed for the insertion through holes in assembled parts. But the screw is an externally threaded fastener capable of being inserted into holes in assembled parts.
• Generally bolts have uniform circular cross section but the cross section in the screw is not uniform, they have pointed tail in most of the cases.
• The bolts are always used with the nuts but the screws are always used without nuts.
• The threads on the bolts are spiral in structure and have smaller pitch. The screw threads are helical in structure and have larger pitch as compared with the bolts.
• The bolts do not have tapered shank but the screw may or may not have tapered shank.
• The bolts mostly require wrenches and spanner for the tightening and loosening purpose but the screw mostly requires screw drivers or Allen key.
• The parts joined with the bolts have greater strength as compared with the screw.
• The reliability of the bolted parts is more as compared with the screwed parts.
• The bolts apply compression on the parts which are with them but the screw doesn’t do that.
• The bolts may available in very large sizes but the screws are available in smaller or medium sizes.