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Spacers and Standoffs
Proper spacing and connecting are common and often critical considerations in engineered situations. Although simple in nature, spacers and standoffs have a wide variety of uses, in a vast array of applications, for almost any industry including electrical, aerospace, equipment manufacturers, medical instruments, open and boxed gearing, and so many more.
These fasteners are ideal when you need a specific distance between parts, where tight fit is required, and precision mating surfaces are desired. Electronic components commonly use these fasteners. These components include circuit boards, panels, doors, gears, and other electronics.
Factors to consider:
- Shape of the fastener (usually hex or round, can be square)
- Outer width or body diameter
- Body length
- Inner diameter or thread size or hole width
- Hole clearance width
Let’s dive deeper into their forms and functions.
What is the function of a Standoff?
Standoffs are a type of threaded separator with a defined length. Standoffs typically help raise one assembly above another. They are critical in providing space between parts and housings and are frequently used in applications that require mounting or stacking.
A standoff is a threaded fastener used to hold two parts a set distance apart. A standoff may have a threaded shaft (male) or a threaded hole (female) at each end. They may, therefore, be designated as male/male, male/female, or female/female.
Standoffs are most commonly male-female, with threading on the male end and on the inside of the female end, which allows the components to be joined together. However, standoffs are also available as both female-female and male-male – which often require further fastening components such as double ended studs or coupling nuts. As you can see the combinations are many.
A male end of a standoff resembles a shoulder bolt; instead of a head, a standoff has another threaded fastener at the other end. Other important parameters are the length (distance between shoulders) and the thread size.
Standoffs may have an external profile that is round, allowing only finger tightening of individual ends, although machine screws and/or nuts can be securely fastened against each other.
Alternatively, a standoff body may have a hexagonal profile enabling tightening using appropriate tooling.
Both spacers and standoffs are commonly used within electronic assemblies. They are also used to provide space for cooling airflow and electrical insulation. They may be referred to as PCB Standoffs. Common materials for such standoffs are brass, stainless steel, nylon polyoxymethylene (POM), polyvinyl chloride (PVC), and ceramics.
Typical standoffs differ from spacers in that they include a threaded shaft or hole, enabling them to be fitted without an additional fastener. These definitions are not always strictly applied, and it is possible to find threaded standoffs referred to as spacers in many catalogs.
What is the function of a Spacer?
A spacer is typically a simple length of tubing which increases the distance between parts and allows a bolt to pass through the center.
Spacers differ from standoffs in that they do generally not have threads. Spacers are typically just a length of tube through which a bolt may be inserted. These distinctions are not always consistently applied, and it is possible to find threaded standoffs referred to as spacers in many catalogs.
A spacer is used to increase the distance between parts being fastened. Spacers are often a length of tube through which a fastener is inserted; a short one may resemble a thick washer. Washers are sometimes used as small spacers.
Both spacers and standoffs are commonly used within electronic assemblies. They are used to provide space for cooling airflow and provide electrical insulation. They may be referred to as PCB Spacers.
Most spacers have a clearance hole through which a bolt is inserted. This means the spacer does not engage with the threads of the bolt. Since the spacer cannot be directly tightened, a round outer profile is most common.
Some spacers have a hexagonal profile combined with a plain hole. These are typically constructed from a relatively soft material such as nylon or brass. They can be used the same way as a conventional spacer but have the added flexibility to be threaded onto a stud or self-tapping screw, using the external flats of their hexagonal profile to apply torque. Therefore, this type of spacer can effectively be turned into a female/female standoff. If threaded, these spacers in essence become coupling nuts.
Common materials for spacers are brass, stainless steel, a variety of plastics, and ceramics.
Double and Single End Studs
Double End Studs are threaded fasteners that have a thread on both ends with an unthreaded portion in between the two threaded ends. Double End Studs or Double end Stud Bolts are threaded rods with thread at both ends and a plain shank equal to that of the nominal diameter; and are designed to be used where one of the threaded ends is installed in a tapped hole and a hex nut used on the other end to clamp a fixture onto the surface that the stud has been threaded into.
Another name that is also sometimes used for Double End Studs is Tap End Stud or “fitted stud”. A Tap End Stud will have different thread lengths on both ends. It has one short thread intended to be used in a tapped hole and often will have Class 5 fit threads to ensure full engagement.
Note that for Metric Double Ends Studs the short thread is not included in the nominal length of the stud. Double-end studs are used for flange bolting or other applications where torching from both ends is necessary or desirable.
Since a double end stud bolt has threads on both sides, it can more easily be used to fasten two components, usually with hex nuts (sometimes locknuts). During the tightening process of a double ended studs, washers can be used to protect the joint surface from damage.
These threaded products are very prevalent amongst gearbox manufacturers and open gearing. Other common applications for double end, tap end single end, and fully threaded studs are in the wind tower, nuclear power, marine, railway, construction, and a wide variety of special machine building. The diversity of these industries demand that studs be made of all types of nonferrous and other exotic materials.