Contactless Thread Inspection

Understanding Contactless Thread Inspection: An Overview

IIT is used for inspection of internal threads and bores. This amazing technology is based on measurement of capacitance between the probe and the thread. IIT is the only automated contactless technology that can check the thread quality along the complete length of any thread.

IIT Components
IIT profile - Nominal thread
IIT profile - Damaged thread
IIT profile - Short thread
IIT profile - Missing chamfer
IIT profile - Loose thread
IIT profile - chip inside thread

Detection Capabilities

How does it work?

The IIT probe works by measuring the space (air gap) between the probe and the part it is inspecting, while it moves linearly in the axis of the bore. During its movement through the thread, the probe collects data (signal) that is then analyzed by software. This data is compared to a reference signal from a master part within a set tolerance range. The width of this tolerance range can be adjusted for different sections of the signal. If the probe’s data falls outside this set range, it indicates a problem with the part (NOK condition).

IIT principle of capacitive thread measurement
IIT Manual Station


System Parameters

Measurement range:

M5 – M25 (custom sensors for higher dimensions)

Measurement speed:

approximately 1 part / s based on application


0.02 mm average

Inspection configuration:

teach-in based on the sample master parts

Frequently Asked Questions

No, IIT is used as a replacement for a GO-NOGO manual thread gages. It does not provide exact dimensional parameters of the threads. 

The measuring range of an IIT probe is approximately 1mm, so a different probe is necessary for different thread sizes. For thread sizes above 16mm, it may be possible to increase the range to over 2mm and measure a small range of sizes with one probe. However, the difference in thread pitch on the same thread diameter has minimum influence on the range and the same probe can be used. 

Yes, any type of thread can be inspected, not only metric, as long as their diameter/pitch is within the size range of 5-25mm. 

Depending on the application, even larger threads can be inspected. However, it is limited to fine threads with smaller pitch, typically up to 1,5-2,0mm. 

Typically, it is up to 60mm from the highest surrounding surface. Special cases can be solved with custom probe designs. 

No, IIT requires electrically conductive material for the inspected part.

Changing probes takes about 10-15 minutes for a trained technician. 

Yes, it is possible. However, the parts must be clean and dry before inspection.  

Positioning and axial alignment of the probe and the inspected thread are mandatory for precise and repeatable measurements. 

Basic results of the inspection can be send to another system using digital signals. ProfiNet communication is possible as an option. Raw measurement data can be stored on an SD card or transferred over FTP. 

There are multiple integration options for IIT. Please check the list above or contact us for more details. 

The maintenance needs for the IIT system are minimal due to its contactless design, which enhances reliability and reduces upkeep. The most common maintenance issues you might encounter include needing to replace a broken cable or a worn-out centering cone. Although the IIT probe is quite durable, if it’s involved in a mechanical accident, replacing the damaged probe may be necessary. 


INSPECTION of Internal thread

Contactless threads inspection

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