Thread Adapters.

What are Thread Adapters & Reducers?

Thread adapters and reducers, also known as thread converters or reducing bushes, are specialised components in Accu's precision nuts range, that let two threaded parts join when their thread specifications don’t match, whether the difference is in size, in pitch or in the standard the thread was cut to. Each is machined from hexagon bar, with flats running the full length of the body. The two ends that tell you which type you are holding: a stud projecting from both faces on a male to male adapter, a stud at one end with a tapped bore at the other on a female to male, or a tapped bore in each face on a female to female. Whichever form it takes, the conversion is carried inside the adapter's own body, so the two original components are never drilled, tapped or altered, and the change can be undone by unscrewing it.

Every thread is cut to a recognised fit class, 2A and 2B on imperial ends and 6g and 6H on metric, so an adapter mates correctly with fasteners and tapped holes sourced from any supplier. That reliability makes them a fixture in prototyping, machine building, tooling, instrumentation, test rigs and maintenance work.

How Thread Adapters & Reducers Work

Installing the right thread adapter comes down to determining if the thread you’re starting from is male or female and whether the thread you need to end up with is male or female. Count the two you are working with and the answer tells you which of the three formats you need. The size conversion is simply a matter of reading across the product name, which lists both threads in full.

Take, as an example, a machine bed drilled and tapped in imperial that has to accept a modern metric sensor bracket. The bed offers 1/2-13 UNC tapped holes and the bracket is designed for M12 hardware, so a male to female 1/2-13 UNC to M12 adapter goes into each hole on the bed and the M12 bracket bolts straight down using standard mating metric hardware. Nothing on the bed needs retapping, the original thread survives intact and if the bracket is later swapped for an imperial one the adapters come out and the holes are exactly as they were. The same pattern repeats across tooling changeovers, retrofitted instrumentation and imported machinery, which is where most of these components end up.

Materials Thread Adapters & Reducers Are Made From

Accu's range of thread adapters and reducers is machined throughout from a single engineering metal, selected because it holds accurate thread form in small sections and needs no protective coating:

• Stainless Steel - (303): A free-machining austenitic stainless, specified to SS 303 / ASTM A582, that cuts clean internal and external threads and resists corrosion in general indoor and industrial conditions.

Sizes & Types of Thread Adapters & Reducers Available

Accu's range of thread adapters and reducers spans a vast number of combinations across imperial and metric threads:

• Imperial Thread Sizes: 2-56 UNC to 1/2-28 UNEF, covering UNC, UNF and UNEF, plus a 1/8 inch NPT pipe thread option.
• Metric Thread Sizes: M4 to M16, in coarse, fine and extra fine pitches.
• Thread Class: 2A and 2B on imperial threads, 6g and 6H on metric threads.
• Hexagon Across Flats: 4.75 mm (0.187 in) to 22 mm (0.866 in).
• Overall Length: 11.91 mm (0.469 in) to 60.33 mm (2.375 in).

The range divides into three categories, each defined by the pair of threads it carries:

• Male to Male Thread Adapters & Reducers: An external thread at each end with a central hexagonal body for joining two female threads or replacing a stud with one of a different size or standard. 
• Female to Male Thread Adapters & Reducers: An internal thread at one end and an external thread at the other with a long hexagonal body for changing the thread while keeping an assembly's existing arrangement or for adding height as a standoff or extension. 
• Female to Female Thread Adapters & Reducers:An internal thread at each end with a solid hexagonal body between them for joining two male threads or coupling two bolts through a single component. 

If no standard combination matches what your project needs, we can design one to your specification through our custom manufacture service. Where the existing thread is unknown, check our guide on how to measure a screw for help identifying the size and pitch. Our full range of nuts and precision screws covers the hardware that goes either side of the adapter.

FAQs

Q: What does a thread adapter do?

A: A thread adapter joins two threaded parts whose threads do not match. It carries one thread at each end, so it accepts the thread you already have and presents the one you actually need, changing the size, the pitch or the standard in the process. Nothing on the original components is modified and the adapter can be removed again at any point.

Q: What is a thread reducer?

A: A thread reducer is a thread adapter that changes the size rather than the standard, stepping a larger thread down to a smaller one or the other way round. A 1/2-13 UNC to 1/4-20 UNC component is a reducer, since both ends are UNC and only the diameter changes. In everyday use the two terms are often swapped, which is why the range is listed as thread adapters and reducers together.

Q: Which type of thread adapter do I need?

A: Work it out from the two unmatched threads you are working with. If both are female, such as two tapped holes, you need a male to male adapter. If both are male, such as two studs or bolts, you need a female to female adapter. If you have one of each and want to keep that arrangement while the size changes, you need a female to male adapter. Each product name then lists both threads in full so you can match the sizes.

Q: Can you convert a metric thread to an imperial thread?

A: Yes and it’s the most common reason these components are bought. A large part of the range pairs a metric thread at one end with a UNC, UNF or UNEF thread at the other, in both directions, so metric hardware can be fitted to imperial equipment or imported metric components can be mounted on existing imperial plant.

Q: What is a hexagonal thread adapter?

A: It’s the standard form these components take. The body is machined as a hexagon so it can be gripped with an ordinary spanner or socket, which is what allows the adapter to be tightened properly rather than turned by hand.

Q: What are thread adapters made from?

A: Every adapter and reducer in this range is machined from 303 stainless steel to SS 303 / ASTM A582 and supplied with a natural, uncoated finish. The grade is chosen for clean thread form and for corrosion resistance that suits indoor, workshop and general industrial use.

Q: Can I use a thread adapter in a load-bearing joint?

A: An adapter introduces an additional joint into the load path, so the connection is governed by the weaker of the two threads and by how much engagement is achieved at each end. For mounting, fixture, tooling and general fixing work that is rarely a constraint. For a heavily loaded or safety-critical joint, assess the adapter as part of the assembly rather than assuming it matches the parent thread.

Q: How do I identify the thread I need to adapt?

A: Measure the diameter across the thread with callipers, then establish the pitch. On a metric thread the pitch is the distance from one crest to the next in millimetres. On an imperial thread it’s the number of threads in one inch. Together those give a designation such as M8 x 1.25 or 5/16-18. A thread gauge is faster and far more reliable on a worn or unmarked thread.

Bespoke Thread Adapters Manufacture.

High precision, bespoke manufacture of Thread Adapters to customer specification. State of the art facilities specialising in both small batch prototyping and large scale manufacture.