A guide to knobs: types, materials and applications
5.5 minutes | 07 Oct 2019
Small plastic knobs. Machine knobs and handles. Plastic threaded knobs. Black metal knobs.
Where do you even start when knobs come in different shapes, sizes and materials, for a variety of applications?
This guide will enlighten you to your choices. We’ll also help you decide which materials you should opt for. First, let’s look at the types of knobs available.
Overview: knob types
|Fluted knobs||The grooves, or fluting, on the side result in a firm grip when turning the knob|
|Lobe knobs||Ideal for medium- to high-torque requirements
Provides exacting control
A knob with three to eight lobes is a clamping knob, sometimes called clamp knobs, which provide positive clamping action
Four lobes are sometimes called hand knobs
|T-Handle knobs||Sometimes called a wingnut knob
A type of lobe knob with two lobes
Easy to grip
Ideal for applications requiring high torque
|Push Pull knobs||Enlarged head allows for finger clearance and good grip|
|Grip knobs||Suitable for confined spaces
Available with knurled texture for no-slip grip
|Ball knobs||Round, as the name implies
Usually used as an operational handle
Ideal for applications that require up-down and side-to-side movement
|Control knobs||Sometimes called instrument knobs
Allows for precise knob positioning and controlled circular motion for instruments and machines
|Knurled knobs||Small pattern on side provides a non-slip grip
Knurled rim helps keep fingers from slipping
Ideal for applications where wet or damp surfaces are involved
|Mushroom knobs||Aesthetically pleasing; finished look
Mushroom design provides a comfortable grip
|Wing knobs||Suitable for confined spaces
Designed for frequent tightening and loosening
Easy to grip
Available with quarter-turn latches, which makes an ideal panel latch for a rack mount cabinet, for example
|Thumb screw knobs||For use instead of a nut or bolt or press fit onto screws
Creates a small knob for clamping or securing
Ideal for environments with limited space
|Tapered knobs||Acts as a handle grip at the end of an operating lever, gear stick or handwheels
Comfortable and secure grip
The environment your application is going in will affect the material you choose. And it’s not just the knob material, but the knob’s insert material that you need to consider. For example, inserts for female threaded knobs are molded into the knob material, such as plastic, at the point of manufacture. It’s the insert that gives your knob the desired strength, which in turn enables the maximum torque.
Additives can be applied to materials at the point of processing to enhance desired characteristics but knowing the material’s original state helps you make an informed decision. With that in mind, let’s start with common knob materials. Plastic knobs make up the majority of your choices. You can also get a quick overview of materials here.
Pros: One of the most popular materials across all industries, nylon offers high-impact resistance. It also gives you excellent resistance to most oils, fuels and greases and has good electrical insulating properties. Plastic hand knobs and plastic threaded knobs are often nylon. Nylon is also used as a material for knob inserts.
Cons: Tends to absorb moisture from surroundings, which can have a negative impact on dimensional stability (yet impact resistance increases). While providing good chemical resistance, nylon can be attacked by strong acids, alcohols and alkalis.
Examples of nylon knobs:
- Fluted grip knobs
- Tapered knobs
- Wing knobs
- Thumb screw knob
- T-Handle knobs
- Lobe knobs, male – also known as hand knobs with threaded stud
Example of a knob with nylon insert:
Pros: Cost-effective phenolic is lightweight and resistant to high impact, heat and wear, and also oils, fuels and greases. It provides excellent corrosion, thermal and electrical resistance.
Cons: It’s a thermoset, which despite its many advantages, does have drawbacks, depending on the intended application. Thermosets are hard and rigid, which also means the material could potentially fail in extremely high-vibration applications. In the case of knobs, however, other material are at work. Take for example, knobs with threaded stud. If it’s made of steel, you can offset this problem.
Examples of phenolic knobs:
- Knurled grip knobs
- Ball knobs
- Mushroom knobs
Thermoplastic elastomer (TPE)
Pros: Flexible TPE is often used as an overlay material to provide a soft, comfortable feel for the end user. An excellent base material in these instances is glass-filled polypropylene, which provides stability and strength. These knobs offer high-impact strength, excellent resistance to ozone and weathering, and good tear and abrasion resistance.
Cons: TPEs cost more than other plastics and are vulnerable to heat aging.
Examples of knobs with TPE:
Pros: PP is semi-rigid. It resists most chemicals and has good heat and fatigue resistance. As a knob, it’s best for light-duty securing and clamping applications. When used as a base material and filled with glass, it becomes extremely strong.
Cons: PP on its own has poor UV resistance and oxidative degradation is accelerated by contact with copper.
Examples of PP knobs:
Low Density Polyethylene (LDPE)
Pros: This low-cost material is semi-rigid, very tough and can be formulated to be weather resistant. Think of water bottles and you have a good idea of LDPE. It provides good resistance to some chemicals and low water absorption. An LDPE knob also has an attractive, ergonomic finish.
Cons: Without additives, LDPE does a poor job resisting the elements and is not resistant to stress.
Example of an LDPE knob:
Pros: Aluminium is lightweight compared to other metals, which is why it’s popular with the aerospace, construction and automotive industries. It can be made to almost any strength, and in cold weather, it becomes stronger. It provides very good corrosion resistance and thermal and electrical conductivity. Also used as a material for knob inserts.
Cons: Although its corrosion resistance is highly rated, it’s not as good as stainless steel.
Example of an aluminium knob:
- Control knob
Example of a knob with aluminium insert:
Pros: Stainless steel is excellent for corrosion resistance, standing up to wet environments. It also retains its strength in high temperatures. It’s hygienic and non-porous, making it ideal in food and medical applications. It also provides an aesthetic appearance, and as a metal, can be recycled. Stainless steel and steel are both used a material for knob inserts.
Cons: If electrical conductivity is important, look elsewhere. Stainless steel performs relatively low in that area. Stainless steels also tend to cost more than plastics, but depending on your application, this could be worth it.
Example of a stainless-steel knob:
- Wing knob
Example of a knob with stainless steel insert:
- Female tapered wing knob
Example of a knob with steel insert:
Pros: Brass is a copper-zinc alloy and often used for as a material for knob inserts due to its integral core strength. It’s wear resistant and frequently used when low friction is required, which includes locks, bearings, and gears. Brass is also used to make screws, nuts and bolts. Brass also has excellent thermal conductivity, which is why it’s often used with as heat exchangers, such as radiators. You’ll also find brass in electrical and other plumbing applications.
Cons: Metals oxidise when exposed to the air, and brass is no different. Still, its corrosion resistance is good. It’s worth noting that the higher the zinc content, the higher the corrosion resistance. Brass is also soft compared to other metals, but that has its benefits, namely, it’s easy to machine. Finally, brass can cost more than other materials.
Example of a knob with a brass insert:
At a glance: Compare materials
To learn more about the material that interests you, click on that material. Note, all materials resist some chemicals better than others. It’s best to check the compatibility of your desired material with specific chemicals.
|Material||Impact resistance||Corrosion resistance||Chemical resistance||Electrical insulator||Electrical conductor|
✔ = poor ✔✔ = good ✔✔✔ = excellent
Which knobs are popular according to industries? This should give you an idea.
|Knob||Appliances||Machinery/ machine tools||Commercial vehicles||Hydraulics||Electronics||Electrical & Data cabinets||Furniture||Medical devices|
|Push pull knobs|
|Thumb screw knobs|