ABP Self-Drilling Countersunk Head Screw
Self-drilling Tek screw with a countersunk (flush) head that sinks fully into the surface — for connecting steel and aluminium profiles up to 5 mm, with approved pull-out and shear data.
Self-drilling — up to 5 mm steelCountersunk flush head (80°)DIN 7504KCold galvanized 5-8 micronSteel & aluminium profilesPH (Phillips) bit
The Adit self-drilling screw (Tek) family
Choose the right self-drilling screw for your head type, profile material and thickness.
ABPCountersunk flush head · steel & aluminium · up to 5 mm ABEHex head Tek · steel & aluminium · up to 6 mm ABEI304SS hex head · aluminium · up to 6 mm BIE / BIE A4Bi-metal stainless · up to 6 mm AUTOSteel Tek · long tip · up to 12 mm BAUTOBi-metal stainless · up to 12 mm ABRDome head steel · up to 5 mm ABR A2Stainless dome head · aluminium · up to 3 mm RS / RS A2Thin flat head · up to 5 mm PS3Long 2-diameter · sandwich panels · up to 6 mm PSLLong 2-diameter · sandwich panels · up to 12 mm BCPThin flat head · up to 2 mm · various colors
Technical specification
| Property | ABP — self-drilling countersunk head screw |
|---|---|
| Screw type | Self-drilling screw for steel, countersunk head (up to 5 mm) |
| Material | SAE J403 1022 steel with heat treatment |
| Standard | DIN 7504K |
| Corrosion protection | Cold galvanized 5-8 micron |
| Head | Countersunk (conical, 80°) |
| Bit | PH (Phillips) |
| Installation tool | High-speed screwdriver (1000-1800 rpm) |
| Also available | Black-galvanized version (NBP) for a dark finish |
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What is a countersunk head self-drilling screw (flush-head Tek screw)? Full explanation
A countersunk head self-drilling screw (Counter-Sink Self-Drilling Screw), also known as a flush-head self-drilling screw or a countersunk-head Tek screw, is an engineered fastening solution that combines a drilling tip (drill flute) at its end with a conical head profile (80° angle) that allows the screw head to sink completely into the surface layer of the material. This structure lets the screw pierce the base material on its own and thread into it in one continuous action – with no need to pre-drill a hole.
Unlike a hex-head self-drilling screw (ABE) that remains protruding above the profile surface, the ABP countersunk head self-drilling screw sinks fully into the material and provides a uniform, smooth and aesthetic surface. That is its major advantage: the screw head does not protrude, does not interfere with adjacent surfaces and does not “catch” on clothing, tools or containers. For applications requiring a smooth, uniform face – the ABP flush-head self-drilling screw is the right solution.
When do you use a countersunk head self-drilling screw? The ABP self-drilling screw suits applications such as: installing metal panels and cladding where a smooth surface is required, connecting light gauge steel and aluminium profiles (Light Gauge Steel), drywall construction, metal finishing, framing, metal furniture and a wide range of industrial and cladding applications where aesthetics matter. Note: the screw requires a pre-formed countersink (Counter-Sinking) in the top material so that its head sinks properly and does not crack.
The advantages of the ABP countersunk head self-drilling screw – not every flush-head Tek screw is the same
- Fully flush head: an 80° conical profile lets the screw head sink exactly to surface level – giving a finished, aesthetic result with no protrusions.
- Approved technical data: accurate pull-out and shear values for every diameter and profile thickness (enabling safe engineering design) – for connecting to steel and aluminium profiles.
- Direct-threading technology: the screw drills and threads in a single action – no pre-drilling for the connection, no accessories and no “dead time” on site (after only a conical countersink in the top material).
- Proven field durability: made of C1035 steel with a cold-galvanized coating – it does not break, bend or disappoint (unlike cheap, undocumented alternatives). Also available in a black version (NBP) for a dark finish.
- Huge range of options: 5 diameters (from ST3.5 to ST5.5), dozens of lengths from 9.5 up to 50 mm, a convenient Ph bit – a complete solution for any specification.
- Support and warranty: designed for contractors and engineers who require engineering backing, load tables and compliance with strict building codes.
Approved technical data – ABP countersunk head self-drilling screw – connection to steel profile
The following data forms the basis for safe structural design. All values in the tables are in kN per single screw. Note: the values detailed below are failure loads (Failure Loads – Nrk/Vrk). For engineering design, an appropriate safety factor must be applied (to obtain the service load). The designer must also verify the tear resistance of the profile itself.
ST 3.5 – countersunk head self-drilling screw – connection to steel profile
| Characteristic failure load parameter (kN) | Steel thickness 0.8 mm | Steel thickness 1.5 mm | Steel thickness 2 mm |
|---|---|---|---|
| Failure load – pull-out (Nrk) | 1.9 | 3.0 | 3.8 |
| Failure load – shear (Vrk) | 1.9 | 1.9 | 1.9 |
| Design load – pull-out (Nrd) | 0.8 | 1.2 | 1.6 |
| Recommended load – pull-out (Nrec) | 0.6 | 0.9 | 1.1 |
ST 4.2 – countersunk head self-drilling screw – connection to steel profile
| Characteristic failure load parameter (kN) | Steel thickness 2 mm | Steel thickness 2.5 mm | Steel thickness 3 mm |
|---|---|---|---|
| Failure load – pull-out (Nrk) | 4.6 | 5.0 | 5.3 |
| Failure load – shear (Vrk) | 2.6 | 2.6 | 2.6 |
| Design load – pull-out (Nrd) | 2.1 | 2.3 | 3.7 |
| Recommended load – pull-out (Nrec) | 1.5 | 1.6 | 2.6 |
ST 4.8 – countersunk head self-drilling screw – connection to steel profile
| Characteristic failure load parameter (kN) | Steel thickness 2 mm | Steel thickness 3 mm | Steel thickness 4 mm |
|---|---|---|---|
| Failure load – pull-out (Nrk) | 5.7 | 7.1 | 7.1 |
| Failure load – shear (Vrk) | 3.6 | 3.6 | 3.6 |
| Design load – pull-out (Nrd) | 2.6 | 3.9 | 5.2 |
| Recommended load – pull-out (Nrec) | 1.9 | 2.8 | 3.7 |
ST 5.5 – countersunk head self-drilling screw – connection to steel profile
| Characteristic failure load parameter (kN) | Steel thickness 2 mm | Steel thickness 3.5 mm | Steel thickness 5 mm |
|---|---|---|---|
| Failure load – pull-out (Nrk) | 5.4 | 8.7 | 9.6 |
| Failure load – shear (Vrk) | 4.8 | 4.8 | 4.8 |
| Design load – pull-out (Nrd) | 2.5 | 4.0 | 4.8 |
| Recommended load – pull-out (Nrec) | 1.8 | 2.9 | 3.4 |
ST 4.8 – ABP countersunk head self-drilling screw – connection to aluminium profile
| Characteristic failure load parameter (kN) | Aluminium thickness 2 mm | Aluminium thickness 3 mm | Aluminium thickness 4 mm |
|---|---|---|---|
| Failure load – pull-out (Nrk) | 2.9 | 4.6 | 6.4 |
| Failure load – shear (Vrk) | 3.6 | 3.6 | 3.6 |
| Recommended load – pull-out (Nrec) | 1.0 | 1.5 | 2.1 |
Geometry and dimensions – ABP countersunk head self-drilling screw
ADIT’s ABP flush-head self-drilling screw series offers dimensions to match every profile thickness and drilling requirement. All models come with a Ph (Phillips) bit for maximum ease of use:
| Screw diameter | Head diameter (mm) | Head thickness (mm) | Bit | Drillable steel thickness (mm) | Available lengths (mm) | Drilling speed in steel (rpm) |
|---|---|---|---|---|---|---|
| ST 3.5 | 6.8 | 2.1 | Ph 2 | 0.70 – 2.25 | 9.5 – 25 | 1800 – 2500 |
| ST 3.9 | 7.5 | 2.3 | Ph 2 | 0.70 – 2.40 | 13 – 38 | 1800 – 2500 |
| ST 4.2 | 8.1 | 2.5 | Ph 2 | 1.75 – 3.00 | 13 – 38 | 1000 – 1800 |
| ST 4.8 | 9.5 | 3.0 | Ph 2 | 1.75 – 4.40 | 13 – 50 | 1800 – 2500 |
| ST 5.5 | 10.8 | 3.4 | Ph 3 | 1.75 – 5.25 | 19 – 50 | 1000 – 1800 |
Quick installation guide – countersunk head self-drilling screw (for steel)
- Form a conical countersink (Counter-Sinking) in the top material: a critical step unique to the flush-head screw – before driving the screw, form a countersink cone in the top material at an 80° angle and a diameter matching the screw head, so the conical head sinks exactly to surface level and does not crack the steel.
- Mark the drilling point: a light tap with a center punch for accurate centering will prevent the screw’s drilling tip from slipping at the start of rotation.
- Prepare the correct screwdriver: use a screwdriver with the speed and torque per the table. An impact driver may be used – but only if you stop immediately once the screw head seats against the profile, to prevent stripping the thread (“wallowing the screw”) and damaging the flush finish.
- Drive perpendicular to the profile: hold the screwdriver at 90 degrees to the material with uniform, continuous pressure. Driving at an angle breaks the drilling tip, weakens the connection and leaves a head that does not sit flush.
- Stop when the head seats: when the screw sinks and reaches the required tightening torque – stop. Over-tightening may crack the steel or damage the thread and finish quality.
All self-drilling screw (Tek) models in the ADIT catalog
- ABE: classic self-drilling steel screw, hex head with washer, cold galvanized. The basic professional series for steel and aluminium profile connections.
- ABEI: identical to ABE but made of 304SS stainless steel. Suitable for aggressive environments, outdoors, coastal areas and the chemical industry.
- BIE / BIE A4: bi-metal screw (stainless body, hard steel drilling tip). Designed for fast, direct drilling into stainless and hard steel (also available in A4/316SS).
- AUTO / BAUTO: self-drilling screw with an extra-long drilling tip – enabling drilling up to 12 mm steel thickness! For heavy profiles. The BAUTO is the stainless bi-metal version.
- PS3 / PSL: extra-long screws for connecting insulated (sandwich) panels. Always come with an EPDM sealing washer for perfect protection against rain.
- ABP / NBP: self-drilling screws with a countersunk (Counter-Sink) flush head for smooth surfaces. ABP – cold galvanized. NBP – black galvanized. This is the series described on this page.
- ABR: self-drilling screw with a round, flat head.
- RSZ / RS A2: self-drilling screw with a small lens head for fine seams and framing.
Engineering consultation + a quality countersunk head self-drilling screw = a complete solution
The market is flooded with cheap self-drilling screws from obscure sources that often break under load, drill slowly, rust quickly, or whose conical head does not sink accurately and leaves ugly protrusions. What sets ADIT Ltd. apart from other suppliers is the knowledge and the standardization. The company’s engineers are available to help calculate and select the screw diameter, screw length and correct model, which saves the cost of field failures and enables standard, approved structural design.
Frequently asked questions – countersunk head self-drilling screw and flush-head Tek screw
What is the difference between a countersunk head self-drilling screw (ABP) and a hex head self-drilling screw (ABE)?
Both screws are self-drilling steel screws that include a drilling tip at the end. The main difference is the head shape: on the ABP (countersunk head self-drilling screw) the head has a conical profile (80°) that lets it sink completely into the material and produce a smooth, uniform finish with no protrusions. On the ABE the head is hexagonal and remains protruding above the surface. The ABP requires a pre-formed countersink in the top material.
What is the difference between a countersunk head self-drilling screw (ABP) and an ordinary countersunk head self-tapping screw?
A countersunk head self-drilling screw (ABP) includes a dedicated tip at its end that lets it drill its own pilot hole in the steel – with no need for an external drill bit. In contrast, a countersunk head self-tapping screw cuts and forms a thread but requires a pre-drilled hole before threading. Using an ABP countersunk head Tek screw saves valuable time and tools on site.
Is pre-drilling required before driving a countersunk head self-drilling screw?
The countersunk head self-drilling screw (ABP) drills its own thread hole. However, a countersink must be formed (an 80° sinking cone) in the top material only – so that the screw’s conical head sinks to surface level and does not crack the steel. A significant saving: there is no need for an external drill bit for the fastener hole itself – the screw handles that.
How do I know which diameter of countersunk head self-drilling screw to choose?
Selecting the diameter of the countersunk head self-drilling screw (for steel) depends on the thickness of the profile you are connecting: the ST3.5 screw is for thin steel of 0.7–2.25 mm. ST3.9 suits up to 2.4 mm. ST4.2 up to 3 mm. ST4.8 (a very common diameter) suits up to 4.4 mm. ST5.5 up to 5.25 mm. For heavier thicknesses, other series should be considered.
What is the difference between ABP and NBP?
ABP and NBP are exactly the same countersunk head self-drilling screw – the same dimensions, the same steel (C1035), the same performance. The only difference is the coating: ABP comes with a cold-galvanized (silver) coating, while NBP comes with a black-galvanized coating. NBP is intended for applications requiring a dark finish – for example, connecting dark panels, black metal furniture, or any application where the screw is visible and needs to blend in with the dark surface.
Does a steel countersunk head self-drilling screw rust outdoors?
The standard ABP/NBP screws come with a cold-galvanized coating intended for protected indoor environments. When installing a flush-head self-drilling screw for outdoor cladding (especially near the sea), it is recommended to consult ADIT’s engineers about the correct model for the specific environment.
Can a countersunk head self-drilling screw (ABP) be used to connect aluminium?
Yes. The ABP countersunk head self-drilling screw is approved for connecting aluminium profiles. The ST4.8 diameter is the most common for aluminium connections and has explicit load data for aluminium (see the table above). Note: using a steel screw in aluminium in humid environments may cause galvanic corrosion – consult ADIT’s engineers regarding the coating and installation environment.
Why does the conical screw head not sink properly and leave a protrusion?
The common causes: no countersink was pre-formed at the correct diameter and angle (80°), the countersink is too small, driving at a crooked angle (not 90 degrees to the profile), or using a screw of a diameter that does not match the countersink. It is important to ensure the countersink diameter matches the screw head diameter (dk) specified in the geometry table.
What is the difference between Nrd (design load) and the characteristic failure load (Nrk)?
The characteristic failure load (Nrk) is the value at which the screw or profile collapses in destructive lab tests – this is the value shown in the tables above. However, you must not design a project according to the failure load! Engineers divide the failure load by a “safety factor” (per international standards) to arrive at Nrd (the safe design load). ADIT provides engineers with all the data needed to perform the calculation.
Can a countersunk head self-drilling screw be removed and re-driven into the same hole?
It is entirely possible to remove the screw and release the connection, but it is strongly not recommended to reuse the same screw in the same hole. Threading in thin steel slightly damages the screw thread and the hole itself, and re-threading may significantly impair the pull-out capacity. In such cases it is better to move up to a larger screw diameter or to place the new screw a short distance from the old hole.
How many countersunk head self-drilling screws do I need to buy – what is the pack size?
ABP screws in diameters ST3.5, ST3.9, ST4.2 and ST4.8 come in packs of 500 or 1000 units per box (depending on the diameter and length). ST5.5 screws come in 500 units per box. For details on available quantities, part numbers and prices – contact ADIT’s engineers.
What is the correct driving bit for the ABP countersunk head self-drilling screw?
ABP/NBP screws use a Ph (Phillips) bit: a Ph No. 2 bit for diameters ST3.5 to ST4.8, and a Ph No. 3 bit for the ST5.5 diameter. The suitable bit is marked PUPHC02 and PUPHL02 (for the smaller diameters) and PUPHC03/PUPHL03 for the ST5.5 diameter. A non-matching bit may damage the screw head and prevent it from sinking properly.
What quantity of countersunk head self-drilling screws is required for a structural connection – how is it calculated?
Calculating the number of countersunk head self-drilling screws required for a structural connection is based on the pull-out and shear loads (Nrec/Vrec) detailed in the tables, according to the type and thickness of the profile, and the loads acting on the connection. ADIT’s engineers are at your disposal for the exact calculation and engineering approval.
Planning a steel or aluminium cladding project? Tell us the profile thickness and load – our engineers will select the correct screw diameter and length and provide the pull-out and shear data.