A guide to thumb screws
Exactly what is a thumb screw? It’s a type of fastener with a large, easy-to-grip head that you can tighten and untighten by hand. It’s typically used in two scenarios:
- Space is too limited to allow for the use of a tool
- A non-permanent fastener is needed for convenient access, reducing maintenance and inspection times
Another advantage to thumb screw fasteners – thanks to their hand-adjustment design – is the reduced occurrence of broken or stripped fasteners, which can happen when using tools.
Thumb screws are not intended for structural applications for obvious reasons – you need permanent fasteners for that. Typically, thumb screws should be avoided for applications that will vibrate, as they’re vulnerable to loosening. Some thumb screws do come with a Phillips slotted head – you can learn more about these heads in What are screw heads, drives and threads? Generally, it’s the slotted head thumb screws, coupled with washers, that can be used for some high-vibration applications.
Otherwise, thumb screws are typically applied to:
- Safety covers for electronic devices and gadgets
- Equipment/machine service panels
- Covers for battery compartments for small electronic devices
Types of thumb screws
Thumb screws are fully threaded and come in two types:
- Type A: these have a shoulder and are also called Type S. The shoulder provides a bearing surface, so that the thumb screw can be tightened against the mating surface.
- How Type A thumb screws are measured: from under the shoulder to the tip.
- Type B: these do NOT have a shoulder and are also referred to as Type P thumb screws. Shoulderless thumb screws are often used as compression fasteners where the tip contacts the mating surface, similar to a set screw.
- How Type B thumb screws are measured: from under the head to the tip.
Overview: examples of thumb screws
Note the oversized heads shown below, which characterize thumb screws. Thumb screw heads often have a diamond pattern or fine knurled ridges for an easy grip.
Knurled thumb screws – Type A
An example of a slotted thumb screw. Made of nylon 6/6 and suitable for outdoor use, resisting weathering and corrosion. Plastic head thumb screws with socket drives are a lightweight option that stands up to vibration.
Nylon wing head thumb screws – Type A
Note the extra-large head. This thumb screw wing provides the user with more leverage and a more comfortable grip for tightening.
Knurled round head thumb screws – Type A
Plastic knurled head thumb screws offer a sure grip. The knurled head prevents thumb and fingers from slipping, enabling easier tightening and loosening.
Nylon knurled oval head thumb screws – Type B
Knurled plastic thumb screws have a flat oval head for added leverage and extra grip for tightening.
Stainless steel knurled thumb screws – Type B
Flat knurled thumb screws made of stainless steel withstand corrosion while providing an easier grip.
Thumb screw knobs
Also called thumb bolts or thumb screw bolts, these shouldn’t be confused with screws, despite their name. Plastic thumb screw knobs can fit over socket-head screws to provide a knob. Also known as thumb screw caps, some can press fit over the screw, while others are attached with the use of a punch or hydraulic press, or a vise.
Female thumb screws are female threaded and sometimes referred to as knobs. You can learn more in A guide to knobs: types, materials and applications.
Materials
The thumb screw material you choose will depend on the application.
- Brass thumb screws
Brass knurled thumb screws are ideal for needs that require high aesthetics. Typically used as light- fixture thumb screw and found in musical instruments and mechanical assemblies. These decorative thumb screws also resist corrosion.
- Bronze thumb screws
Common thumb screws for wood. With good corrosion resistance, these are used in light applications to fasten metal or metal to wood.
- Plastic thumb screws
An excellent all-rounder, acetal or nylon knurled head thumb screws are cost effective and lightweight, fastening different materials that range from plastics to wood.
- Stainless steel thumb screws
Used in applications ranging from camera tripods to telescopes. With an aesthetic finish, stainless steel thumb screws are also perfect for applications demanding hygienic solutions, such as healthcare and the food and beverage industry.
At a glance:
|
Priority |
Brass |
Bronze |
Plastics |
Stainless steel |
|
Aesthetics |
x |
x |
||
|
Corrosion resistance |
x |
x |
x |
x |
|
Cost effective/lightweight |
x |
|||
|
Stands up to sterilization |
x |
Thumb screw sizes
These fasteners are available in a range of sizes including large thumb screws, long thumb screws and miniature thumb screws, so you should easily find what you need. The U.S. measures fasteners in inches, which is called standard, while in the UK, you’ll find metric thumb screws. We encourage you to learn more by checking out What is the difference between metric and standard fasteners?
You’ll also learn about the standards used. For instance, DIN 464 knurled thumb screw standards are German but recognized worldwide, including in the U.S and the UK.
Download free CADs and try before you buy
Free CADs are available for most solutions, which you can download. You can also request free samples to make sure you’ve chosen exactly what you need. If you’re not quite sure which solution will work best for your application, our experts are always happy to advise you.
Whatever your requirements, you can depend on fast dispatch. Request your free samples or download free CADs now.
Questions?
Email us at sales@essentracomponents.com or speak to one of our experts for further information on the ideal solution for your application 800-847-0486.