What is a bolt?
Strictly meant to be mated with a pre-tapped hole or nut, a bolt is a fastener with external threading. Bolts come in a variety of materials, most commonly steel (in a variety of grades) and stainless steel. They are most commonly available in American (Inch) Standard and Din/ISO Metric. Simply speaking a bolt is meant to be torqued/tightened by the nut, versus a screw which is meant to be torqued/tightened by the head. This is why in our catalog break down
Hex Head Cap Screws (aka Hex Bolts)
are found in the Screw Section
. For more info on Bolts vs. Screws please see this Wikipedia "Screws" article
Battery Bolts, Square Head, Steel, Zinc Plated
Bolts - Bent Anchor Foundation Bolts
Eye Bolts, Open End, Steel, Zinc Plated
Bolts - Heavy Hex Bolts Structural
Bolts - Lifting Eye Bolts
Bolts - Precision Swing Eye Bolts
Step Bolts, Truss Head, Square Neck, Steel, Zinc Plated
DIN 186, Metric, T-Head Bolts, Class 4.8 Steel, Plain
Timber Bolts, Dome Head, Steel, Hot Dip Galvanized
Track Bolts, Round Head, Slotted Drive, Ribbed Neck, Full Thread, A307 Steel, Zinc
DIN 3570, Metric, U-Bolts, Steel, Zinc Plated
You also see a variety of fastener styles designated as "Bolts" at The Fastener Resource Center.
Bolts are generally broken down into the following 5 categories:
Hex and Square Bolts
ANSI/ASME B18.2.1 (1981)
- Square Bolts
- Hex Bolts (Hex Cap Screws, Heavy Hex Bolts, Heavy Hex Structural Bolts)
- Square Lag Screws
- Hex Lag Screws
Round Head Bolts
ANSI/ASME B18.5 1978
- Carriage Bolts
- Step Bolts
- Flat Carriage Bolts
- T Bolts
ANSI/ASME B18.15 1985
Slotted Head Cap Screws
B18.6.2 1972 (R1983)
ASTM A193 & ASME B16.5
Some basic information regarding bolts that Aspen Fasteners offers from inventory.
A low to medium carbon steel bolt with a square head, often referred to as a square head bolt. The shape of the head provides a greater bearing surface. Available in coarse thread, Grade 2 steel with a zinc finish
Flat head Slotted Cap Screws:
Often used for close tolerance joints where head clearance and a low profile is critical. Available in diameters from 1/2" to 3/4" and lengths up to 3" in coarse thread, steel with zinc finish.
Grade 2 Steel Hex head Cap Screws:
Hex head cap screws or hex bolts have a six sided hexagonal shaped head with machine screw threads. Hex Bolts are generally used in a pre-tapped hole or with a hex nut. There are several common terms for hex bolts that include hex cap screws, hex machine bolts and when fully threaded hex tap bolt. Manufactured from low carbon steel, these screws meet SAE J-429 Grade 2 specifications. Least expensive and ideal for non-critical applications where they are not subject to extreme temperatures or excessive stress. Available in coarse thread, with zinc or black oxide finish. Grade 2 hex cap screws are stocked in a full range of sizes. Grade 2 hex head cap screws have no head markings.
Grade 5 Hex Head Cap Screws:
Grade 5 hex cap screws are manufactured from quenched and tempered medium carbon steel. They are typically used when greater tensile strength is needed. Grade 5 steel provides the lowest yield-to-tensile ratio of tempered steels. Domestic and Import varieties are available in coarse and fine thread with clear zinc finish (class 2A threads). They conform to ASTM A-354 and SAE J-429 Grade 5. Available in diameters from 1/4" to 1-1/2" and lengths up to 14". Grade 5 hex head cap screws most often have 3 lines in some arrangement as head markings. Click here to view hex head cap screw/hex bolt head markings.
Grade 8 Hex Head Cap Screws:
Grade 8 hex cap screws are manufactured from medium carbon steel quenched and tempered to a high degree. These screws meet ASTM A-354 BD, SAE J-429 Grade 8, and SAE chemical and mechanical specifications. Grade 8 hex head cap screws have greater tensile strength than Grade 2 or Grade 5 bolts and are most often used in applications where high stress is encountered. Available in coarse and fine thread, import and domestically made, with yellow zinc finish (class 2A threads). Stocked in diameters from 1/4" to 1-1/2" and lengths up to 14". Grade 8 hex head cap screws most often have 6 lines in some arrangement as head markings. Click here to view hex head cap screw/hex bolt head markings.
Hex head cap screws are also available in stainless steel 18-8 or stainless steel 316. Metric threading in either Grade 10.9 plain steel or Grade 8.8 zinc is also available.
Designed for wood-to-wood or wood-to-metal applications. These self-anchoring round head bolts have a square neck to resist turning when the nut is being tightened. Available in Grades A307 (with zinc , galvanized and black oxide finishes); and Grade 5 (with zinc finish) and Grade 8 (with yellow zinc finish) in diameters from #8-32 to 3/4" and lengths up to 6-1/2". The appropriate head markings are found on grade 5 and grade 8 carriage bolts.
Round Head Square neck carriage bolts are also available in stainless steel 18-8. We stock fully threaded carriage bolts in all but Grade 8. Fully threaded grade 5 carriage bolts are also known as Shaker Screen Bolts.
Flat head carriage bolts are also self-anchoring with a square neck to resist turning but their low profile head requires less clearance. Available in Grades A307 with plain or a clear zinc finish.
Ribbed Neck carriage bolts are used in softer materials to keep the bolt from turning when the nut is being tightened. Available in Grade A307 steel in a clear zinc finish
Ribbed Neck Track Bolts are designed specifically for use in the installation of garage doors. The ribbed neck is used in softer materials to keep the bolt from turning when the nut is being tightened. They are fully threaded, with a truss style head that is slotted. Available in Grade A307 steel in a clear zinc finish.
Commonly used in conveyor/elevator systems. For use in applications with rubber belting, these bolts are made with a large flattened Norway head, also preferred where a low profile is required. Also available in steel with a zinc finish. Stocked in diameters from 1/4" to 3/8" and lengths from 3/4" to 3", Measured from top of head.
An eye bolt is a wire form with a loop on one end and machine screw threads on the other end. Eye bolts are commonly used to attach cables to objects. Eye bolts without a shoulder are not recommended to be used for angular loads. Available in steel with a clear zinc finish and to be used as a temporary, light duty fastening system. Also known as Bent Bolts or Turned Eye Bolts.
Locking Serrations under the head maintain a tight grip when loosening forces are present. The flanged head also provides greater bearing surface and eliminates the need for a washer. Available in carbon steel with a zinc, black oxide and green zinc (grounding screw) finish, Grade 5 steel with zinc finish, and also stainless steel 18-8 .
Generally used for automotive applications. Flanged head provides greater bearing surface and eliminates the need for a washer. Available in Grade 8 steel with a black phosphate and oil finish. Hex head frame bolts are also available in stainless steel 18-8.
Part wood screw, part machine screw. Also known as Table Leg Bolts as they are often used in furniture manufacturing. One end is screwed into wood, and the exposed end provides a machine threaded stud. Stocked in diameters from #6-32 to 1/2" and lengths up to 6" in steel with zinc finish. Hanger bolts with plain center (unthreaded center) for easier installation are also available. Full thread and plain center hanger bolts also available in stainless steel 18-8.
Hex Head Tap Bolts:
These bolts are also known as fully-threaded Hex Cap Screws, and have a variety of uses in construction, agriculture and automotive applications. We carry a complete line of mild steel (zinc ), Grade 5 (zinc ) and Grade 8 (yellow zinc ) tap bolts. Available in coarse and fine thread, and in diameters 1/4" to 1" and up to length of 10". Hex head tap bolts also available in stainless steel 18-8.
Hex head and square head machine bolts are partly threaded hex bolts. Available in coarse and fine thread, and in diameters 1/4" to 1-1/2" and up to length of 12". We carry a complete line of steel hex head machine bolts in zinc and galvanized finishes. Plain square head steel machine bolts are also available.
Made from Grade 5 and Grade 8 carbon steel, these bolts are excellent for use on snow plows, farm equipment and similar heavy equipment. Available with a #3 flat head style only. Conforms to ASME B18.9 SAE J429. Stocked in diameters from 1/2" to 3/4".
A self-anchoring bolt with a square neck to resist turning when the nut is being tightened. For use in softer materials as the larger diameter head will not pull through. Also preferred for its lower profile. Available in zinc.
Designed for use in structural joints, these bolts are made from hardened steel and meet ASTM A-325 specifications. Plain and hot dipped galvanized finishes available. Stocked in diameters from 1/2" to 1-1/4" and lengths to 6". Head markings for an A-325 bolt is a stamped "A325" somewhere on the head.
For high temperature, high strength applications, these studs meet ASTM A-193 Grade B7 specifications. Stamped at one end and properly chamfered. Available in plain steel and stocked in diameters from 1/2" to 1".