Stainless Steel Thread Adapters – when the thread doesn't fit the component

It's one of the most common little hurdles: you want to fit a sensor, a mirror or a line, but the existing thread doesn't match the connection. Drilling out and re-cutting isn't an option when the thread has to be made smaller, and hunting down a completely different component is often unnecessary or simply not available. This is exactly where the thread adapter comes in: it sits between the mount and the component and joins two different threads – a male thread on one side, a female thread on the other – tight and load-bearing.

The adapters are made from A2 stainless steel. On a component like this that's not a minor detail but a decisive point: anyone using an adapter permanently in an engine, on a line or outdoors doesn't want to have to undo it after one winter because it has rusted.

A2 stainless steel (material 1.4301) is corrosion-resistant and therefore suited to exactly the spots where an adapter typically sits: in constant contact with oil, fuel, coolant or compressed air, often in an exposed position and subject to the weather. An adapter made of bare steel or aluminium of dubious quality will sooner or later develop rust or an oxide layer there – with the result that the joint seizes up and causes problems at the next service.

Stainless steel stays clean, keeps its strength and can still be undone and reused years later. The adapters shrug off the temperatures that occur during engine operation without any loss of strength, as well as contact with more aggressive media. For a component that can be screwed in once and then forgotten, it's the right choice – and the reason we deliberately do without cheaper materials.

The thread combinations come in two versions, depending on how they can be tightened at the installation point. The abbreviations stand for:

• IH = internal Hexagon
• EH = external Hexagon

Which version makes sense is decided by the accessibility at the installation location:

• IH – internal Hexagon: the adapter is tightened from the inside with an Allen key. This design is shorter and low-profile – ideal where space is tight or the adapter should sit as flush as possible.
• EH – external Hexagon: the adapter has a hexagon for an open-end or ring spanner. This lets you apply more torque. This version is somewhat longer.

Examples:

• Adapting sensors: Temperature and oil-pressure sensors come with a fixed connection thread that rarely matches the existing service port, blanking plug or oil-filter cover exactly. Common engine threads such as M10×1, M12×1,5, M14×1,5 and M16×1,5 can be brought to the sensor thread with the right adapter. Anyone retrofitting a CUMPAN and installing a temperature or oil-pressure sensor in a position not provided for as standard often can't avoid an adaptation like this.
• Imperial and metric connections: When pressures or temperatures need to be measured at a specific point, a reduction from the imperial to the metric system or vice versa is often required.
• Add-on parts: Bar-end mirrors, bar-end indicators and hand guards need a matching thread in the handlebar end. If the handlebar has a female thread, it can be brought to the required size of the add-on part with an adapter.
• Lines and senders: Matching combinations are also available for adapting connections on lines or additional senders.

A concrete example is fitting at the handlebar end: the adapter brings the existing thread in the handlebar to the size that the part being fitted needs – such as a bar-end mirror or a hand guard. It's tightened via the internal hexagon (IH) with the Allen key; the stainless-steel adapter then sits permanently and corrosion-free in the handlebar end.

A thread that doesn't fit isn't a problem specific to motorcycles. The adapters make sense anywhere different thread sizes have to be joined cleanly and corrosion-resistantly:

• Measurement and sensor technology in pneumatics and hydraulics: pressure gauges and pressure sensors often have connections in 1/8” BSP or 1/8” NPT – classic instrument connections that are linked to metric threads with the appropriate adapters.
• Compressed air and compressors: reductions and connection adaptations on compressed-air lines, manifolds and tools.
• Water and air lines: adapting connection threads in the home, garden and workshop, where corrosion resistance matters.
• Machine and plant engineering, test rigs: adapting sensors, senders and lines to existing threads.
• Model making and hobby workshop: anywhere a small, precise thread reduction is needed and a robust, rust-free part is the right choice.

In outdoor and damp areas in particular, the stainless steel plays to its strengths: once screwed together, it stays functional and can be undone again later.

All available thread combinations at a glance. IH = internal Hexagon, EH = external Hexagon. For the IH versions, the size of the internal hex key (ISK) is given; for the EH versions, the wrench size across the external hexagon (SW).

The list covers the most common combinations but isn't exhaustive. If you need a thread size that isn't listed here, we'll check whether we can manufacture it on request. A short message with the desired thread pairing and the preferred design (IH or EH) is enough.