Non-Preloaded Bolt Proof Strength Chart

As part of the Non-preloaded chapter for the Bolted connections (only ISO Metric), I made a quick chart. In the chart, you can obtain the proof load strength of the most typical bolt sizes (from M3 to M42), for regular and fine thread pitch.

The chart is divided in three sheets:

-ISO 898-1 for Steels and Alloy Steels

-ISO3506-1 for Stainless Steels.

-ISO 8839 for non-ferrous materials.

You have also two inputs per sheet, where you can control the safety factor/load factor, and a second one to control the shear/tensile ratio.

Click in the following link, and download the excel chart

https://mega.nz/#!DgJDFbpI!ALrjYCUnFxJElN5NkiTPB9kjYahifR8wwRqvTlj1gYo

Bolt Joint Introduction

1. Introduction

Bolted joints are among the most common type of fastening connections. Similarly to the screws, a bolt joint requires a series of elements that forms what can be called a bolt group. The bolt group consist in the following items:

Bolt: Similar to a screw, the bolts are design following some ASTM and ISO standards. Bolts can be made with different type of heads; which includes hexagonal head, round head, or square head.

Nut: Bolt connections require a Nut, which also has its own ASTM and ISO standards. The nut has to be chose of the same material that the Bolt. Special types of Nuts, such as Locking Nuts can be used to reduce the self-opening risk during frame vibration, or fluctuating loads.

Always select a nut which proof tensile stress is equal or higher the proof tensile stress of the bolt.

Washer: Not strictly necessary for all the bolt connections; washers are recommended to be installed under the bolt head as well as under the nut, in order to improve the effectiveness of a pre-load connections, but also to protect the clamped material.

For pre-loaded bolted connections, specific standard washers, made of hardened steel are required.

1.1 Bolt vs Screw

Although many people use the term bolt for everything that is not a wooden screw, actually it’s difficult to separate what a bolt is from what a screw is.

Bolts are similar to screws, but they strictly need to be tighten using a nut; meanwhile screws are normally threaded to a tapped hole.

Screws and bolts have normally quite different designs, as it can be seen comparing a mushroom head bolt with a socket head cap screw. However, for the specific group of Hexagonal Bolts and Hexagonal head cap screws, they are much alike.

To differentiate them, it is important to know that:

-Structural bolts require to be used paired with a nut, while hexagonal bolts do not require a nut.

-The proper method to apply a bolt to a connection is fixing the head, and turn the nut; while in a screw (even if you are using a nut), you should tight the head of the screw.

-Both may use different standards, which could be for dimensions/tolerances or for the mechanical properties. Although not always, the bolt standards, tend to produce thicker heads than in the hexagonal screw (for example comparing the ISO 4014 & the ISO 8765, or the ASTM vs the SAE).

To make the separation easier, I personally suggest using ASTM and ISO 4014 type of standards for bolts, and use other type of configurations (rather than hexagonal head) when using screws. If Hexagonal head screws are the best option to use, use them in accordance with Standards SAE J249 or ISO 8765 as shown in the screw Unit.

1.2 Bolt Classifications

There are different groups of bolts used regularly in structural designs. The most typical configurations are the following:

Hexagonal Head Bolt

They are the most common type of Bolts used. They can be used in all type of bolted connections, with good rates of torsional resistance, as well as tensile/shear strength. Although they can be tighten thought the head (using a wrench), the design method is using the wrench to fix the head, and tight the nut around the bolt.

Mushroom Head Bolt

Extensively used in structural and building construction (such as in bridges), this bolt has a round head (flat from the bottom) to clamp the parts together, and a square neck to prevent the bolt of turning during the tightening operation. Therefore, this type of bolt doesn’t require a wrench to fix the head.

Flat Head Bolt

It is similar to the mushroom, but using a conical flat head, which flush with the surface of the clamped part.

Square head Bolt

Similar to the hexagonal bolt, large flat sides make them easy to grip with a wrench and keep them from rotating in square holes.

They are not as common as the other two types of bolts.

1.3 Dimensions Standards

Metric

Based on the ISO standards for Metric dimensions:

ISO 4014: Regular hexagon head bolt product grade A and B

ISO 4015 Hexagon head bolt product grade B (reduced shank)

ISO 4016: Hexagonal head bolt product grade C

ISO 4017: Fully threaded body hexagon head bolt

ISO 4162: Hexagon Flange bolts

ISO 8765: Hexagon head bolt with fine thread. Product grades A and B

ISO 8677: Mushroom bolt with square neck

ISO 7411: Hexagon bolts for high strength structural bolting (threads according to ISO 888). Product grades C.

For the nuts, the ISO dimensional standards are:

ISO 4032: Regular hexagon nut

ISO4034: Hexagon nut class C

ISO 4035: Low profile nut

ISO 4161: Hexagon nut with flange

ISO 4775: Hexagon nut for high voltages

ISO 7040: Locking hexagon nut with Nylon insert

Apart from the ISO, there are other metric standards such as the ASME in the USA:

ASME B18.2.6M: Hexagon heavy head bolt as well as the Nuts (after 2012).

Imperial

In case of using imperial bolts:

ASME B18.2.6 is used for structural bolts for ASTM A325 and ASTM A490.

While regarding to the nuts:

ASME B18.2.2: Hexagon nut dimensions.

1.4 Material and strength Specifications

Metric

The following ISO standards are set to determine the material and properties of the bolts and nuts:

ISO 898-1: Steel and Alloy Steel Bolts, screws, and male fastener material properties

ISO 898-2: Steel and Alloy Steel Nuts and female fasteners material properties

ISO 3506-1: Stainless Steel Bolts, screws and male fasteners material properties

ISO 3506-2: Stainless Steel nuts and female fasteners material properties

ISO 8839: Bolts, screws, studs, and nuts non-ferrous materials

There are other metric standards equivalents to the ISO, such as:

ASTM F568M: similar to ISO 898-1

ASTM F593: Similar to the ISO 3506-1

ASTM F468M: Similar to ISO 8839 for fasteners

ASTM F467M: Similar to ISO 8839 for nuts.

Imperial

Material Specifications for Bolts [2]

ASTM A307: Low or medium carbon steel

ASTM A449: Medium carbon steel; quenched and tempered

ASTM A235: Medium carbon steel; quenched and tempered

ASTM A354: Medium carbon alloy steel; quenched and tempered

ASTM A490: Medium carbon alloy steel; quenched and tempered

ASTM A574: Medium carbon alloy steel; quenched and tempered

ASTM F835: Medium carbon alloy steel; quenched and tempered

ASTM F593: Stainless Steel

ASTM A193: High temperature Resisting Steels and Stainless Steel

ASTM F468: Non-ferrous fasteners

Material Specifications for Nuts [2]

ASTM A563: Low and medium carbon steel, may be quenched and tempered

ASTM A194: Medium carbon steel

ASTM A194: AISI 304

ASTM F467: Non-ferrous nuts

1.5 Coating Specifications

It is common that the Steel bolts are protected from the environment using different types of coatings. The protection required is commonly against oxidation and mildly against corrosion.

Although there are different types of protective coating that can be applied to bolts and nuts, the most commonly found are the following: [6] [7]

ISO

ISO 4042: Electrodeposited coating

ASTM [10]

ASTM F1941/F1941M: Electrodeposited coating

ASTM F1136/F1136M: Zinc/Aluminium Corrosion Protective

ASTM 2329/F2329M: Standard specification for Zinc coating and Hot-dip requirements for application to carbon steel and alloy steel fasteners

ASTM F1137: Phosphate/Oil corrosion protective coating

If the environment or use requires high corrosion resistance, other type of bolts are required, normally Stainless Steel (titanium or aluminium if the weight is an important factor). When using steel and Stainless steel bolts, be careful when they touch aluminium or galvanized steel parts. If the conditions for galvanic corrosion are met, the more noble metal will become the cathode and the more active the anode; this condition increases the anode’s rate of corrosion. [8] [9]

In these conditions, any element present to break the galvanic corrosion conditions will be sufficient to stop the anode’s corrosion. This “element” could be using insulated washers, add other type of coating (such as paint or polymer coatings)…

See this in a video https://www.youtube.com/watch?v=U3rkeVndhtg