Self-tapping fasteners

TEPRO® K' in K'

Self-tapping and self-locked.
With TEPRO® K' in K' plastic fasteners solutions for plastic assemblies.


Self-forming, self-tapping, adjustable and reverse-locked.

In the medium to long term, direct screw-fittings with metallic screws in plastics can lead to problems with the fit and failure of the thread connection due to movement, vibration and temperature changes.

It follows that it is more natural to attach a plastic component using a screw that is also made of plastic.

The solution here is the development of the K' in K' (plastic in plastic) screw fastening principle.

This product is made by Böllhoff

Method / principle

The K' in K' screw fastening technology is based on special thread geometry with two offset thread halves. The K' in K' thread forms or cuts into the cylindrical bores for integrated solutions for permanent and reversible fastenings that are self-locking, self-tapping, self-forming, adjustable and able to provide tolerance compensation.


Our K' in K' fastening solutions can be found in a wide variety of applications. They are used in the automotive industry to attach instrument panels, mounting supports and lightsas well as in the general industry for office furniture.

Product benefits
  • No corrosion
  • Chemical resistance
  • Electromagnetic compatibility
  • Weight reduction by use of plastic throughout
  • Secure fastening

Product benefits

There are many good reasons for using our products.

Strength and options.
Point by point.

No corrosion

High temperature resistance, stiffness and strength. Thanks to threads made of high-performance engineering plastics.


Reasonable disposal. Unlike with metal inserts there is no need for the costly separation of metal and plastic.

Secure fastening

The torque is higher when unscrewing the fastener. That means the fastener is reliably secured against coming loose.

Detailed description


Effectiveness and functionality of thread profiles

The K' in K' screw fastening principle uses patented thread geometry which is easily identifiable by two offset thread halves. The K' in K' thread forms or cuts into the cylindrical pilot bore in the plastic. A chip flute running the length of the screw enables effective tapping and forming without obstructing the thread flanks. Thanks to the resulting cutting angle and adjacent clearance angle the screw assembly is driven home using minimal torque.

When unscrewing the fastener, however, the torque is considerably higher. That means the fastener is reliably secured against coming loose.


TEPRO® K' in K' – Drawing of the K' in K' principle

1) Chip flute / chip angle
2) Clearance angle
3) Direction of rotation
4) Clearance angle

Product variants

Every project deserves a tailor-made solution.

Learn more about the product types and find the right variant for your particular application.

Self-tapping fasteners

TEPRO® K' in K'

Our self-drilling or self-cutting plastic screws.



The K‘ in K‘ thread as an integral part of a customised solution.

Tolerance compensation


The function of the K' in K’ thread is equally important when it comes to so-called “banjo screws”. The K' in K' thread cuts its own pilot thread into the existing plastic bore.



Find out more: related downloads.

If you would like to know more, simply download the relevant brochures.

Title Language Version File Download
TEPRO® K' in K'
Threaded plastic fasteners solutions for plastic assemblies
English 4330/15.02 431 kB / PDF
English 4330/15.02 431 kb / PDF

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