Drilling capacity is one of the key selection parameters for a self-drilling screw used in steel construction. It describes the thickness range that the drill point is intended to penetrate before effective thread formation begins in the supporting steel.
Drilling capacity is not the same as screw length
The overall screw length defines the physical length of the fastener. Drilling capacity relates specifically to the drilling function of the point. A long screw can still have a limited drilling capacity, while a shorter screw may use a point intended for a thicker steel support. The drilling requirement and the clamping requirement must therefore be checked separately.
What the drill point must achieve
During installation, the drill point first creates the hole through the steel layers that must be penetrated. Thread engagement should develop only after the drilling sequence has progressed sufficiently for the screw to form a reliable load-transfer interface in the supporting material. Point geometry, cutting edges, flute shape, point length and chip clearance all influence this process.
Why insufficient drilling capacity causes problems
If the steel thickness to be drilled exceeds the validated capacity of the point, the thread can begin pulling the screw forward while the drill point is still removing material. This increases installation force and heat and can lead to slow drilling, damaged or burned drill points, incomplete penetration or an unreliable installation.
Why excessive drilling capacity is not automatically better
The highest available drilling capacity is not automatically the best choice. A point designed for thicker material may use a geometry that is unnecessary for thin supporting steel. The selected screw should match the actual support-thickness range and the manufacturer's validated application window rather than being chosen only because it can drill more material.
Drilling thickness and supporting-steel thickness are different checks
The drill point may need to pass through several layers before the final supporting steel is reached. The total thickness penetrated by the point can therefore be greater than the thickness of the support in which the thread ultimately develops. Both conditions matter: the point must penetrate the complete drilling build-up, while the supporting steel must still provide adequate thread engagement and structural resistance.
Clamping range is a separate requirement
Even when the drill point can penetrate the assembly, the screw must also have a suitable fastening or clamping range. Panel thickness, sheet build-up, spacers, washers and other layers affect the required screw length. Passing the drilling-capacity check does not by itself confirm that the selected screw length is suitable.
Drilling capacity and structural resistance are different checks
A screw can drill successfully and still be unsuitable for the design load. Pull-out, pull-over and shear resistance depend on additional parameters such as screw diameter, thread geometry, supporting-steel thickness and strength, connected-sheet thickness, edge conditions and the governing failure mode. Drilling capacity confirms installation capability, not structural capacity.
Installation speed and pressure also matter
Self-drilling performance depends on the interaction between the fastener and the installation tool. Excessive rotational speed can overheat the drill point, while unsuitable pressure or speed can impair chip removal and increase drilling time. Installation settings should follow the validated range for the selected screw system and the actual substrate condition.
Engineering selection sequence
- Identify every steel layer that the point must penetrate.
- Determine the total drilling build-up at the actual fixing location.
- Identify the thickness of the final supporting steel separately.
- Select a screw whose documented drilling range covers the drilling condition.
- Verify the screw length and clamping range independently.
- Check pull-out, pull-over and shear resistance where structural performance is required.
- Use installation speed, pressure and depth control appropriate to the selected screw system.
Product-specific verification
Drilling capacities, clamping ranges and connection resistances are product-specific. Values established for one screw geometry, material or manufacturer should not be transferred to another fastener without supporting technical documentation or test evidence. JOPAL selection should therefore be based on the documented data for the specific product and application being considered.
This resource explains selection principles. Final product suitability, drilling range and resistance must be verified against the applicable JOPAL technical data for the specific fastener and project condition.
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