Different factors play a role in the assembly. The mounting receptacles, the tools, the correct drilling, and of course different materials.

General information about drilling

The drill should of course be adapted to the type of material and the thickness of the board. It may even be necessary to drill a stepped hole to ensure a perfect fit and centering of the mounting receptacle.

In the case of fibrous materials such as glass fiber boards (HGW2372.1 / FR4), a slightly larger hole must be drilled than for other materials, as the fibers are set up in the hole.
Mounting methods
It must also be taken into account whether a receptacle is to be mounted via the guide diameter or the press ring diameter.
External influences
The assembly of receptacle always requires special care. Various parameters such as speed, feed, spiral groove length, material type and panel thickness influence the drilling behaviour.


What to pay attention to?

The mounting of receptacle always requires special care.

Parameters that influence the drilling behavior

  • Speed
  • Feed
  • Spiral groove length
  • Material type
  • Plate thickness

The borehole recommendations given in the technical data are therefore guide values for FR3/FR4 and serve as a basis for your own drilling tests.

It is therefore advisable to carry out your own drilling tests in order to achieve a secure fit of the contact part.

Overview table

Which drill size do I use?

In the case of fibrous materials, such as glass fiber plates (HGW2372.1 / FR4), the hole size must be slightly larger than for other materials, as the fibers will stand up in the hole.

It must also be taken into account whether to mount over the guiding diameter or the press ring diameter of a receptacle.

Pointing Accuracy and Wobble Position

Pointing accuracy defines the repeatability of a contact probe when contacting the test specimen. The accuracy is influenced by the guide clearance and the required manufacturing tolerances, the plunger length and the type of plunger guidance. However, factors such as the receptacles and their mounting in the test fixture should not be neglected. The most important factor for the accuracy of the probe is the wobble position of the probe tip at the time of contact.

The wobble position is the lateral deviation of the plunger head from the center axis of the probe. The accuracy of the probe specified in the technical data of the contact probes is essentially identical to its maximum wobble position.

Receptacles for Contact probes

For reasons of interchangeability, spring contact probes are often mounted with receptacles into which the probe is inserted or screwed. The electrical connection is made via the receptacle, which is available with different connection types.



Receptacles with collar on top have a fixed projection height and guarantee the tightest seat with very low tolerances. Receptacles with press ring can be used in two ways. Either the press ring is used as dead stop or it is inserted into the mounting plate, which results in a variable projection height. For receptacle insertion into the mounting plate, a special insertion tool is necessary.

Connection of Receptacles

Almost all receptacles are available with solder or crimp connection. Wire wrap connections are frequently used for test fixture manufacturing because they can be wired automatically. Some receptacles (especially those with very small diameters) are available with pre-assembled wires. Additionally, to connect coaxial probes, special connecting elements can be used.

Types of Receptacles

At ICT/FCT test fixtures mainly plug-in probes are used. However, in some applications, particularly at modules for wire harness and connector tests, threaded probes are used, which are screwed into the receptacles. Threaded probes guarantee a secure seat because they do not move out of the receptacle even under difficult conditions. Knurled receptacles ensure a firm seat of the receptacle in the drill hole. For switch probes and coaxial probes, FEINMETALL has developed special receptacles called “combi-receptacles“, which enable a solder free exchange of these probes. Further receptacles with integrated switch function are available, that are frequently used in combination with twist proof probes. Airtight receptacles are also used in adaptations where vacuum or negative pressure is used.

Airtightness for receptacles

If the air tightness class is specified for FM receptacles, it is defined as follows:

Airtight I corresponds to a leakage rate
< 0,7 cm3/min.

Airtight II corresponds to a leakage rate
0,7–7 cm3/min.


By using spacers, different projection heights can be achieved without the need for new probes or receptacles. They can also be used for tolerance compensation. They are usually made of uncoated brass, as they have only a mechanical function and no electrical function.


Spacers are inserted between the receptacle and the pluggable contact probe mounted.

It is also possible to use several spacers in combination to reach other projection heights.

Always make sure that the dimples of the mounting receptacle still hold the contact probe. Therefore a maximum distance of 5.0mm is possible.

Assembly tools

Different tools for mounting and dismounting receptacles and contact probes are explained below.


Insertion tools for receptacles

Differences of insertion tools for receptacles briefly explained.
All receptacles with a fixed stop (collar) can be used with the FEWZ-...E0. Press rings on receptacles can also be used as a stop. Here, the guide pin of the tool is used to stabilize the receptacles to ensure the best possible mounting of the receptacles.
All receptacles with press ring can be mounted to different height levels with corresponding insertion tools, e.g. FEWZ-...Exx. Please always specify the required dimension "X"!
For receptacles with press ring and frequently changing height levels, the variably adjustable FEWZ...EV is recommended. A scale on the adjustable tool facilitates assembly.To ensure that the anti-rotation protection of probes is actually effective, the receptacles must be loaded into the test fixture already aligned during assembly. This can be done by means of an FAWZ... alignment tool. The alignment tool can also be clamped in a hand lever press. Advantage: One-time alignment of the alignment tool in the fixture.

Insertion tools for contact probes

Insertion tools for pluggable contact probes. The contact probe is inserted into the receptacle until the probe is seated on the pressure points. The probe is then pressed into the receptacle. The insertion tool is specially made of plastic to avoid unnecessary damage to the plunger tips! Depending on the structure of the contact probe, the tool can also sit on the probe collar.

Screw-in tools contact probes

Screw-in tools for threaded contact probes are modular. Bits and handles can be ordered individually. The handles are color-coded according to wrench size (SW). Depending on requirements, a standard handle, a handle with screw-in aid and an adapter piece for the cordless screwdriver are available for each bit. Likewise, a correspondingly suitable bit is available for the different probe types.

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