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Contact us You can contact us using any of the methods below. Unit 3 Durham Lane Armthorpe Doncaster South Yorkshire DN3 3FE England +44 (0)1302 836010 +44 (0)1302 836012 sales@npfasteners.com
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NORTHERN PRECISION LTD
Accreditations Northern Precision Ltd operate a quality management system in accordance with ISO 9001:2008. The ISO 9001:2008 standard is recognised worldwide and you can be assured of the benefits of working with a certified company knowing that our management systems are constantly assessed and improved.
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NP
NORTHERN PRECISION LTD
Specialist Fasteners for Sheet Metal
+44 (0) 1302 836010
+44 (0) 1302 836012
Tel:
Fax:
sales@npfasteners.com
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Self-Clinching fasteners provide strong load bearing male or female threads, pins and access hardware in thin steel and aluminium panels.   Installation is neat and easy, simply locate the fastener into a pre-prepared (punched or drilled and reamed) hole and apply a parallel squeezing force to embed the fastener into the panel.   Self-Clinching fasteners work by utilizing a special clinch feature. When the part is pressed into the hole,  the parent material is displaced and cold-flows into the clinch feature, effectively locking the fastener into the panel, providing excellent torque-out and push-out performance. Self-Clinching fasteners require a parallel squeezing force to be applied for correct installation. Equally important is the length of time the force is applied. Sufficient time must be allowed for the cold-flow clinching process to work (this is often referred to as the dwell time when installing on a hydraulic press).   Self-Clinching fasteners CANNOT be installed with a hammer blow as the force would only be applied for about a 100th of a second which is insufficient for the cold flow process to work. There are so many permutations of fastener type, size, panel material characteristics, hole preparation,  installation and tooling configuration. This is the reason we state that the performance figures given for our fasteners are offered as guidance only. To ensure successful  installation and achieve the best possible performance from our fasteners we’ve put together a selection of Do’s and Don’ts so you can avoid some of the common mistakes and pitfalls.
DO Punch or drill the correct size hole in the panel as specified for the fastener. Install from the punch side of the panel if possible. Make sure that the Shank or pilot of the fastener is located squarely in the hole before applying pressure. Apply a parallel squeezing force. Make sure the panel is held perpendicular to the Punch / Anvil. Apply enough force to totally embed the knurling so the shoulder of the nut is squarely in contact with the sheet. For Studs and Standoffs, the head should be completely flush with the top of the panel. (See installation page for specific install procedure for non-flush fitting fasteners). Pay attention to the specified minimum / maximum panel thickness for the fastener you are installing. Pay attention to the specified maximum panel hardness limit for the fastener you are installing. Pay attention to the minimum centreline to edge limit as specified for the fastener you are installing. Make sure that installation tooling is in good condition and within specification for the fastener you are installing. Punches and anvils should be made from hardened tool steel. A worn or deformed punch or anvil will result in a sub-standard installation and poor performance. DON’T De-burr or chamfer the hole on either side of the panel - this will remove material that is required during the clinching process and will reduce performance. Over-install the fastener - this will distort the panel and depending on the type of fastener possibly result in tight threads or other fastener damage. Try to install the fastener with a hammer blow - a sustained parallel squeezing force is required to allow the panel material to be displaced and cold-flow into the clinch feature. Install 300 series stainless fasteners into stainless steel. Specify a fastener designed for use in stainless steel. Install steel or stainless fasteners into aluminium panels before anodising or finishing. Install the fastener into the pre-painted side of a panel. Performance will be compromised. Install the screw from the head side of the fastener. You must install from the opposite side of installation.
√  X
Do not remove any extra material or chamfer the hole as this could result in improper installation or reduced performance.
PAY ATTENTION TO THE MAXIMUM RECOMMENDED PANEL HARDNESS WHEN INSTALLING SELF-CLINCHING FASTENERS Ensure that you are installing into a panel that is ductile and at or below the published maximum recommended hardness for the fastener. Hardness figures are shown in HRB (ROCKWELL HARDNESS B SCALE). Installing in to too hard material will result in failed installation / poor performance / a damaged fastener.
Ensure that attention is paid to the minimum hole centreline to edge dimension for each fastener. Installing too close to an edge or bend could result in improper installation or reduced performance. Minimum centreline to edge dimensions shown for each fastener apply to one edge only. If this distance is applied on multiple sides there will be significant panel distortion unless the panel edges are supported during installation. Any panel distortion will reduce the amount of material cold-flowing into the undercut and thread position and performance will be compromised.
C/L to Edge C/L to Edge X  √  Min C/L to Edge Min C/L to Edge
A PUNCHED HOLE SHOWING TYPICAL SHEAR CHARACTERISTICS
PUNCH SIDE
DIE SIDE WITH 10% CLEARANCE
ROLL-OVER ZONE
Ø7.11
Ø7.34
2.30
SHEAR ZONE
FRACTURE ZONE
FOR BEST PERFORMANCE IT IS PREFERABLE TO INSTALL SELF-CLINCHING FASTENERS FROM THE PUNCH SIDE
Tight hole dimension. Accurate fastener placement. More material available to cold-flow into undercut. Best Performance.
Loose hole dimension. Inaccurate fastener placement. Less material available to cold-flow into undercut. Reduced performance.
INSTALLING FROM PUNCH SIDE
INSTALLING FROM DIE SIDE
Min. C/L to Edge
Bend Radius
This area of the panel must be flat
Mounting hole in panel must be round and in specification
Remember to allow for  installation tooling clearance
X
When installing near a bend, it is important that you still pay attention to the minimum centreline to edge dimension for the fastener you are installing. However, In this scenario it is measured as the distance from the hole centreline to the outside of the bend radius. Failures that occur are different from the the issues caused by installing too close to an edge. Some examples are failed installation, poor performance or the fastener drifting from hole centreline during installation due to work hardening of the panel at or near the bend on one side of the hole. The panel must be flat as shown in the diagram. Make sure that there is adequate room for the actual installation tooling.
When installing multiple fasteners in the same panel, they must be spaced far enough apart to avoid distorting each other’s holes. Installing too close together can produce distortion, buckling or stress wrinkling of the panel and it will be impossible to maintain a smooth flat panel surface. To determine the minimum required distance between two or more fasteners, take the minimum centreline to edge dimension for the fastener you are installing and add 1/2 the diameter of the second mounting hole.
Fastener hole size 5.4mm Min. C/L to Edge dim. 6.9mm
Fastener hole size 5.4mm Min. C/L to Edge dim. 6.9mm
9.6mm Min. hole C/L (6.9 + 2.7)
If you have any questions relating to the correct use of our fasteners or need advice about a particular application or scenario, please give our sales team a call on +44 (0) 1302 836010, they will be happy to help you or consult with our technical team for advice or finding a solution for you. We are always happy to supply samples for testing and application development. For some applications you can send in your chassis/panel and we can recommend a fastener and carry out installation / testing for you. A range of common issues, causes and solutions when installing self-clinching fasteners can be found here. Installing self-clinching fasteners in harder panel materials.
SELF-CLINCHING FASTENERS DO’S & DON’TS