Introduction to Different Types of Screws Based on Thread Types

Stainless steel screws are one of the most important types of screws in use today. These screws are distinguished on the basis of their physical features – heads, drives and threads. In the previous blogs we have discussed the prominent head and drive types. This post introduces you to all major screw thread types that are in use today.

Important Thread Varieties of Stainless Steel Screws You Need to Know About

Screw threads are a combination of recesses and ridges on the screw body. These threads help fix a screw in place through a compatible thread inside a nut or pre-drilled hole. The interior threads of the nut or another location where the screw is being fixed is known as female and exterior thread of the screw is known as male. Many times screws are referred to by their thread types.

Following are some of the major thread varieties known to us:

• Machine Screw Threads: These are the standard threads which are designed to fit into a pre-drilled interior of a tapped hole or nut. These screw threads are distinguished with their unique features which lend high accuracy when these screws are fitted into their partner thread. These machine screw threads are used on setscrews, bolts and machine screws.
• Self-tapping Screws: These thread-forming or self-tapping screws feature threads which are designed to tap their own holes. These screws are used in lighter materials such as plastic or wood as well as in plywood, aluminum castings, zinc die castings, etc.
• Type U Screws: These screws feature multiple coarse spiral threads which are usually driven by a hammer and possess a button shaped head. The type U screws are designed for tamper proof fixing in metal and plastic castings. These screws have a button or round shaped heads.
• Coach Screws: These screws are designed to create their own thread in pre-drilled holes. Coach screws incorporate a wood screw type rolled thread which is a soft version of imperial.
• High-low Screws: The High-low screws are distinguished by their alternating heights. These screws are designed for low-density materials and plastics. The screw derives high pull strength due to its design. Also, this design helps reduce the instance of plastic cracking.
• Woodscrews: The screws have deep and coarse threads which help them go deeper in the wood. They are further distinguished by the following types:

i. Cut Thread Woodscrews: These wood screws have defined and sharp threads between a tapered shank and gimlet point.

ii. Long Thread Woodscrews: These threads have the same type A spaced threads and gimlets as discussed above. However, these threads are extendable to the full length underneath the head. These threads are used for timber materials such as particle board, craft board, etc. These screws provide high pull out strength as well as longer thread engagement.

iii. Rolled Woodscrews: These threads employ a type A spaced thread and are distinguished by rolled taper points. These threads are used for joining, furniture, and cabinet making.

• Sheet Metal Thread Screws: These screws are distinguished by their coarse threads which are used in projects involving thin sheet metals.
• Cut Threads: These types of threads are distinguished by their specific cutting. These threads are further divided into two varieties – Type 17 and Type 25. Type 17 is designed for fixing metal sheets, aluminum sheets, fibro-cement sheets, etc. Type 25 is designed for use in hard plastics or die castings.

The above mentioned screw thread types and their uses will give you an idea about the best thread for your project. However, you can always approach a thread expert like Norwood Screw Machine Parts to find a suitable thread for your project.