About Fastener Materials

General

Fasteners are manufactured in a wide range of materials from common steel to titanium, plastic and other exotic materials. Many materials are further separated into different grades to describe specific alloy mixtures, hardening processes, etc. In addition, some materials are available with a variety of coatings or platings to enhance the corrosion resistance or alter the appearance of the fastener.

Fastener material can be important when choosing a fastener due to differences between materials in strength, brittleness, corrosion resistance, galvanic corrosion properties and, of course, cost.

When replacing fasteners, it is generally best to match what you are replacing. Replacing a bolt with a stronger one is not always safe. Harder bolts tend to be more brittle and may fail in specific applications. Also some equipment is designed so that the bolts will fail before more expensive or critical items are damaged. In some environments, such as salt water, galvanic corrosion must also be considered if changing fastener materials.

Materials

Stainless Steel

Stainless steel is an alloy of low carbon steel and chromium for enhanced corrosion characteristics. Stainless steel is highly corrosion resistant for the price. Because the anti-corrosive properties are inherent to the metal, it will not lose this resistance if scratched during installation or use.

It is a common misconception that stainless steel is stronger than regular steel. In fact, due to their low carbon content, many stainless steel alloys cannot be hardened through heat treatment. Therefore, when compared to regular steel, the stainless alloys used in bolts are slightly stronger than an un-hardened (grade 2) steel but significantly weaker than hardened steel fasteners. Unless great care is taken, stainless fasteners are susceptible to seizing up during installation, a phenomenon known as galling.

Most stainless steel fasteners are much less magnetic than regular steel fasteners though some grades will be slightly magnetic.

What is a Lead Screw?

A lead screw is sometimes referred to as a “power screw” or a “translation screw”. They are used within motion control devices to transform rotary or turning movements into linear movements.

Lead screws are threaded bars of metal and a threaded nut which is in direct contact with the screw; this generates sliding friction as opposed to rolling friction from other alternative devices (such as a ball screw). Rotational motion will turn the screw, causing the nut to move along in a linear motion. This, therefore, converts the motion from rotary to linear.

They can be used for either vertical or horizontal movements and can use linear glides for support where necessary. They can be operated either manually or mortised depending on the application in hand.

Where the screw itself is generally constructed of stainless steel, the nut can be various materials depending on what is better suited for the application. Heavy-duty applications will require a metal nut whereas other applications may require a plastic one.

What is a lead screw used for?

Lead screws are commonly used as a component within linear motion control systems. They are well suited to instrument grade applications such as;

Laboratory and life science equipment including DNA sampling

Fluid handling devices

Engraving

Rapid prototyping

Data storage

Inspection

Heavy lifting applications – a metallic nut must be used for this type of application

When selecting a lead screw, it is important to take into consideration the speed, thrust, accuracy and repeatability of the application. If you require assistance selecting a lead screw or would like to discuss your application please contact us.

Advantages of Using Lead Screws

Lead screws have many advantages – some of these are;

High load-carrying capacity

Compact

Easy to design into a system

Minimal number of parts

Smooth operation

Quiet

Require little maintenance

As well as the above advantages, lead screws from Heason also have the following;

Competitively priced

Flexible configurations

Available in screw diameters as small as 6mm

Self-locking, therefore, do not require a braking system