Hex Cap Screws and Hex Bolts

Hex cap screws and hex bolts feature a hexagonal head that is utilized during the tightening of the fastener. A hex cap screw utilizes a washer face under the head and a chamfered end, while the hex bolts lack those features and requires a nut. These fasteners are commonly used in construction, machine parts, and maintenance repairs. Hex cap screws and hex bolts are manufactured in variety of sizes, finishes, grades, and materials depending on application.

Finish

Chrome

This finish improves appearance and provides mild corrosion resistance. It can also increase surface hardness, which improve abrasion resistance, reduces friction, and prevents seizing. This finish is shiny and aestheticly pleasing.
EcoGuard®

This finish provides some of the highest corrosion resistance. This finish has been tested at a minimum of 1000 hours in the salt spray test for corrosion, eliminates hydrogen embrittlement, and is free of toxic metals. This a great corrosion-resistant, environmentally-friendly finish.
Plain

This bare metal surface has no finish for improving appearance or corrosion resistance, which is very low if the material is steel. Often the surface has been oiled, which improves lubricity. Plain finish fasteners can be used indoors or in outdoor environments where corrosion protection is not an issue.
Yellow Zinc

This irridescent electroplated zinc finish, also known as Yelllow Zinc Chromate or Dichromate, provides very good corrosion resistance and protection against rust. This finish should not be used in marine or high salt spray environments.
Zinc

This finish, also know as zinc plating, zinc chromate or dichromate provides good corrosion resistance and is the standard for many hardware fasteners. It is an electroplated zinc layer covered with a chromate post-treatment. The zinc protects the steel from corrosion and the chromate layer protects the zinc from degrading. It is a popular finish because of its protection, cheapness, and ease of coating. Slightly less corrosion resistant than yellow zinc, it is a versatile finish that is best used indoors. This finish should not be used in marine or high salt spray environments.

Grade

18-8

A general designation for the most common and popular stainless steel (300 Series), 18-8 refers to the 18% chromium and 8% nickel. Its strength has a range from the middle to low end of the grade scale. All 300 series stainless steel share the ratio of chromium to nickel with varying other elements improving different properties. It has higher corrosion resistance than the 400 series stainless steels and is non-magnetic.
2

This grade is from the SAE scale and made of low carbon steel. This classification is low on the grade scale.
316

The second most common stainless steel grade, this material is stronger than grade 2, slightly weaker than grade 5,or generally as strong as medium to low carbon steel. It is on the low middle end of the grade scale. It is used in severe corrosive environments more than 304 stainless steel. As such it is used in more industrial settings like process chemicals, textiles, bleaches, salt water, and rubber. It is also used in surgical implants. The DIN/ISO denotation for a very similar grade is A4-70.
400

Commonly known as Monel 400, this nickel-copper alloy has similar uses to Stainless Steel in terms of corrosion resistance. However, Monel 400 is of a higher grade. It is stronger than SAE grade 2 yet weaker than SAE grade 5.
5

This grade is from the SAE scale. Made of medium to low carbon steel, it is of medium strength on the grade scale.
6/6

This is a specific designation of a polyamide or nylon plastic. This material is lightweight, non-magnetic, non-corrosive, non-toxic, non-flammable, and non-conductive. It is much weaker than the SAE standard grade 2 yet great in low strength applications where weight is at a premium.
8

This grade is part of the SAE classification; it is the minimum standard of the automotive and structural industries and is used in high-temperature applications. Grade 8 is near the high end of the grade scale, although there are higher grades and strengths for more specialized fasteners.

Material

Aluminum

Aluminum fasteners are a light weight alternative to steel fasteners. Aluminum is soft, non-magnetic, and corrosion resistant. These fasteners offer good electrical and thermal conductivity, and a good strength-to-weight ratio.
Brass

Brass is a soft, non-magnetic fastener material that offers corrosion resistance, heat and electrical conductivity, and cosmetic appeal. Brass fasteners may be found in electronics, plumbing, and marine applications.
Monel

This 2/3 nickel and 1/3 copper material is an alloy developed by the Special Metals Corporation. It has very good strength and is similar in strength to medium carbon steel, however, due to its strength it has poor machining properties. Its composition also provides it with excellent corrosion resistance in specific highly corrosive environments of sea water, hydrofluoric acid, sulfuric acid, alkalines. With the ability to retain its strength at very high and low temperatures it is one of the best materials to resist extreme elemental conditions. Applications include marine fasteners and chemical processing.
Nylon

Nylon is a lightweight, wear resistant, non-magnetic, non-conductive, corrosion resistant fastener material often used in electronics applications. Nylon fasteners are commonly made of nylon 6/6, which is generally able to withstand oils, greases, and solvents. Many nylons melt rather than burn and have the ability to self-extinguish. Nylon fasteners may swell from moisture absorption, degrade under UV exposure, or fail in high strength applications.
Silicon Bronze

Silicone bronze is a high strength fastener material popular in naval and marine environments, and sewage disposal applications. Silicon bronze is known for its high thermal conductivity, non-magnetic properties, and high resistance to corrosion, even in harsh environments such as those where brines or gases are present.
Stainless Steel

Stainless steel is steel combined with alloying elements, principally chromium, to enhance corrosion resistance and impart other desired properties depending upon the alloying elements in use and their proportions. Many stainless steel fasteners are non-magnetic or less magnetic than regular steel fasteners.
Steel

Steel is the most common fastener material due to its strength properties. Unalloyed steel may be surface treated to enhance corrosion resistance and other desirable properties.

System of Measurement

Imperial (Inch)

Also known as the Unified system, this measurement system is primarily used in the USA. It uses feet, inches and fractional inches as its basic measurements.

Metric

Also known as the SI system, this measurement system is used across the globe. It is based on multiples of ten and uses meters, centimeters, milimeters as its basic measurements.

Thread

Coarse

Also known as UNC/UNRC, it is the most common threading used on bolts, screws and nuts. These threads have faster assembly times, but have less sensitive adjustment. They generally thread easliy, yet are slightly weaker than fine threads.
Extra Fine

Also known as UNEF/UNREF, this is the finest threading. Extra fine threads are used when engagement length is short.
Fine

Also known as UNF/UNRF, this threading is used when higher tensile strengths are needed. These threads have slower assembly times with more sensitive adjustment. They are susceptible to cross threading and are generally stronger than coarse threads.

Type

Hex Bolt

Hex bolts feature a hexagonal head with no washer face beneath. These general duty fasteners do not have chamfered threads on the point (end where the nut is threaded) and are used in conjuction with a nut. They are best for connecting rough projects of wood on wood and in general light duty househould construction.
Hex Cap Screw

This hexagonal headed fastener is designed to be screwed into a tapped (pre-threaded) hole or secured with a nut. The underside of these heads are washer faces and the point ends are chamfered. These are used in more specialized situations than hex bolts.
Hex Cap Screw - Drilled Head

These hex cap screws are further secured by wire locking, binding screws together with a safety wire threaded through drilled holes in the fastener head. The safety wire also provides a visual signal that the screw has been properly tightened.
Hex Cap Screw - Left Hand Thread

Left handed hex cap screws tighten when the fastener is rotated counterclockwise. This is useful in rotating machinery or assemblies that may cause a normal right handed fastener to loosen.
Hex Cap Screw - Nylon Patch

Nylon patched screws find their utility when a mechanical locking mechanism is required on a fastener used in a tapped hole.
Hex Cap Screw - Slotted Head

Slotted hex cap screws have a linear recess in the fastener head for use with flat head screwdrivers. The hex head enables wrench access when there is no overhead space for the flat head screwdriver.
Tap Bolt

Tap bolts are fully threaded hex head fasteners able to accommodate multiple joint thicknesses. Tap bolts may be a good choice when bolt thread length needed is unknown.