Universal Fastening System – The Grooved Pin Principle

The fastener incorporates in its design three longitudinal grooves swaged or formed into a cylinder of material, which has the effect of increasing its diameter. In the case of unheaded pins, this may be over part or all of the length of the pin and may be of a tapered or parallel form. In the case of headed pins, the grooves are always parallel and, with blind drive pin rivets, the pin is used to expand the rivet and is retained in the body of the rivet.

Groove compression

In each product, installation of the grooved pin causes the grooves to compress, this compression produces outward pressure on the walls of the hole and in so doing secures location of the pin. Diagram 1 shows compression taking place as a section through a grooved pin.

Simple, Reusable, Resistant to Shock and Vibration

When compared with more traditional taper pins, plain pins, keys or locating pins which rely on ‘interference’ at one point on the pin and also require a reamed or precision formed hole, the grooved pin principle can be seen to represent a significant improvement. Resistance to withdrawal occurs wherever the grooved diameter is compressed; it can be over the whole length of the pin instead of just at one point as with traditional pins. This advantage is represented in diagram 2.

Grooved pin diagram

Why Use Grooved Pins?

Simple Hole Preparation
  • No reaming or threading of the hole prior to installation is required
Resistance to Shock and Vibration
  • Because the pin is held in position under elastic tension, it cannot easily be dislodged in harsh environments
Total Range
  • Standard pin types are available for many applications, eliminating the need for more labour intensive or complex fasteners, or custom designed expensive parts
They are Reusable
  • When removed from the application, the grooves recover their form and can be reused many times with only minimal reduction in pull out performance
Simple Installation
  • Providing correct procedures are followed, there is no need for special installation equipment for small volumes. Where high production quantities are anticipated, the pin can easily be fed and does not require sophisticated installation equipment
  • The Tappex Grooved Pin is a solid steel fastener giving high shear strength and good wear resistance

Installation Information

Hole Preparation
  • When drilling the hole for installation of a grooved pin, a standard twist drill should be used of the same nominal diameter as the ungrooved pin. Use hole tolerance H9 for pins under 3mm and H11 for 3mm and above, although in steel a slightly larger hole will only marginally affect withdrawal loads. Tappex Grooved Pins are produced with a minus tolerance on the ungrooved diameter to allow easy fit.
Pin Strength
  • The tensile strength of the pin must be the same as or higher than the strength of the component material.
  • Parallel groove pins require significantly higher installation forces than tapered groove pins. To eliminate the chance of any difficulty during installation, a 60° counter sink should be incorporated into the hole and the pin should be slightly lubricated prior to installation. During installation it is important to ensure correct alignment between the pin and the hole.

Installation Forces

These figures give data on average installation forces required for tapered and parallel grooves. Generally the force to remove a pin is slightly more than the force required to install it.

Tapered Grooves – insertion force in kgs per length of groove
Tapered grooves

Parallel Grooves – insertion force per mm of groove
Parallel grooves

Standard Tolerances
Body Diameter, dome and length

Tolerance on body diameter and dome
Grooved pins tolerances table
d1 = Body diameter C = Height of dome L = Body Length

Tolerance on length ‘l’

The Grooved Pin designs are subject to certain standard tolerances, which are listed here. Other specified tolerance information is provided is provided in our literature.
1mm – 3mm
3mm – 6mm
6mm – 10mm
10mm – 18mm
18mm – 30mm
30mm – 50mm
50mm – 80mm

Product Identification

The part number is made up of the nominal diameter and effective length. The example shown here is for Grooved Pin S8 – third length centre tapering grooves – DIN 1475. A standard part number assumes a plain steel material. Other materials should be noted at the time of specifying by quoting the appropriate material reference.

Material Specifications
Grooved Pins, Headed Grooved Pins
The Tappex Grooved Pin system is manufactured in Germany, consequently material specifications relate to DIN standards. Various options are available and these are given below together with DIN reference numbers where appropriate and the corresponding British Standard number where available. Various Standards of finish are available where applicable – if more information is required, please contact our  Sales office.

grooved pin material spec

These Grooved Pins are produced in Germany by Kerb-Konus-Gesellschaft and Tappex Thread Inserts Ltd. are their Sole Technical Distributor in the U.K. and Eire.

Select Type

The following are downloads relating to the Groove Pins range, although a downloads may also be applicable to other product ranges. General information can be found on our downloads page.

If you can’t find what you are looking for, why not simply give us a ring on +44 (0) 1789 206600.

Tappex Downloads - PDF

Product brochure with overviews and descriptions of products Trisert, Trisert-3, Foamsert, Multisert, Microbarb, HiMould, Anti-creep-spacers, Multi-riv, Male Inserts and our Installation Equipment

Tappex Downloads - PDF

Universal Fastening System. The Grooved Pin range has provided fastening solutions in a number of industry sectors including: machine building, chemical equipment, manufacture, precision engineering, automotive and electrical engineering.