BCP Extra-Flat Head Self-Drilling Screw

Extra-flat head self-drilling screw with an integrated drill point — pierces and threads steel and aluminium profiles in a single action, with a low Phillips-drive head that does not protrude above the surface.

Extra-flat headSelf-drilling — no pre-drillingST 4.2 · PH2 driveSteel up to 4.4 mmA2 stainless (SS304) versionApproved pull-out & shear data

What is the BCP extra-flat head self-drilling screw?

The BCP extra-flat head self-drilling screw is a unique self-drilling screw with an especially low, extra-flat head and a Phillips (Ph) drive, designed for connections that require a low-profile head that does not protrude above the surface. The screw incorporates a drill point at its tip, allowing it to pierce the profile and thread in a single action – with no pre-drilling.

The BCP extra-flat head self-drilling screw is especially suited for fastening steel and aluminum profiles up to 4.4 mm thick (steel version) or up to 2.0 mm thick (A2 stainless steel version), and is used for sliding doors, windows, mortise locks, and any application requiring a thin, aesthetic, low-head connection.

When do you use the BCP extra-flat head self-drilling screw? Typical applications include: assembling metal frames, connecting aluminum profiles, installing cladding and panels, manufacturing metal furniture, and anywhere a protruding head could snag the side or catch on moving parts.

The advantages of the BCP self-drilling screw – not every self-drilling screw is the same

Extra-flat head: a low, radius-rounded head that slides and does not catch on moving parts – ideal for sliding doors, windows, and locks.
Approved technical data: precise pull-out and shear values for every profile thickness, enabling safe and documented engineering design.
Direct-threading technology: the screw drills and threads in a single action – no pre-piercing, no additional accessories.
Available in a range of versions: steel with cold galvanizing (BCPZ, BCPB, BCPN, BCPZ BL) and A2 stainless steel for humid and aggressive environments (BCP A2).
Engineering support and warranty: ADIT engineers are available to help select the right model, calculate loads, and meet technical specifications.

Approved technical data – loads for steel profiles

The following data forms the basis for safe structural design. All values in the tables are in kN per single screw. Note: the shear capacity does not account for tear-out of the profile itself (steel or aluminum). The designer must verify the profile’s tear-out capacity in order to determine the final shear value.

ST 4.2 – connection to a steel profile

Load Parameter (kN)	Steel Thickness 2 mm	Steel Thickness 2.5 mm	Steel Thickness 3 mm
Characteristic Failure Load – Pull-Out (Nrk)	4.6	5.0	5.3
Characteristic Failure Load – Shear (Vrk)	2.6	2.6	2.6
Design Load – Pull-Out (Nrd)	2.1	2.3	3.7
Design Load – Shear (Vrd)	2.0	2.0	2.0
Recommended Load – Pull-Out (Nrec)	1.5	1.6	2.6
Service Load – Shear (Vrec)	1.4	1.4	1.4

Geometry and dimensions

The BCP extra-flat head self-drilling screw is available in diameter ST 4.2, in two standard lengths suited to most drilling applications in steel and aluminum profiles:

Parameter	Value
Screw Diameter (dk)	ST 4.2
Head Diameter (dk)	8 mm
Head Thickness (K)	0.7 mm
Bit	PH 2
Outer Diameter incl. Thread (D)	4.2 mm
Screw Core Diameter (d)	3.1 mm
Pitch (P)	1.4 mm
Drill Point Length (Z)	4 mm
Available Lengths (L)	14 mm, 23 mm
Maximum Drillable Steel Thickness	0.7 – 2.0 mm (BCP A2) / up to 4.4 mm (BCP steel)

Maximum recommended fastened steel thickness by screw length (ST 4.2)

Screw Length (mm)	Maximum Fastened Steel Thickness (mm)
9.5	–
13	4.3
16	0.3
19	10.3
22	13.3

Models, part numbers and versions

The BCP series is available in a range of coatings and materials, allowing you to select the extra-flat head self-drilling screw suited to every environment and application:

Model	Coating / Material	P/N 4.2×14	P/N 4.2×23	Units per Box
BCPZ	Cold Galvanized (Zinc)	BCPZ4214	BCPZ4223	500
BCPB	White Galvanized	BCPB4214	BCPB4223	500
BCPN	Black Galvanized	BCPN4214	BCPN4223	500
BCPZ BL	White Head Only, Galvanized Body	BCPZ4214BL	BCPZ4223BL	500
BCP A2	A2 Stainless Steel (SS304) – Passivated	BCPA24214	BCPA24223	500

Important note for the BCP A2 (stainless steel) version: this screw is intended for use with aluminum only and is not designed to drill steel – the drill point will burn out due to the lower hardness of the stainless steel. To drill steel in a corrosive environment, use the bi-metal BIE models.

Quick installation guide

Mark the drilling point: a light tap with a center punch for accurate centering will prevent the drill point of the extra-flat head self-drilling screw from slipping at the start of rotation.
Prepare the right driver: use an impact driver. Recommended speed: in steel 1000–1800 rpm, in stainless steel 600–1000 rpm. Exceeding the speed causes the drill point to burn out.
Drive perpendicular to the profile: hold the driver at 90 degrees to the material with even pressure. Driving at an angle breaks the drill point and produces a defective connection.
Stop when the screw head seats: when the head of the self-drilling screw seats against the profile – stop. Over-driving will strip the thread and weaken the connection.

Suitable driver specifications

Anchor Type	Material	Drilling Speed (rpm)
ST 4.2 (BCP steel)	Steel	1000 – 1800
ST 4.2 (BCP A2 stainless)	Stainless / Aluminum	600 – 1000

Frequently asked questions

What is the difference between the BCP extra-flat head self-drilling screw and a standard self-drilling screw (ABE)?

The BCP extra-flat head self-drilling screw is characterized by a low, beveled head profile (Extra-Flat Head, 65° angle) that seats partially into the profile and does not protrude above the surface. This is in contrast to the classic ABE screw, which has a tall hex head with a washer. The BCP is intended for connections requiring minimal protrusion – such as sliding doors, window frames, and profiles containing moving parts.

What is the difference between the BCPZ, BCPB, BCPN, and BCPZ BL models?

All of these models are an extra-flat head self-drilling screw made of C1035 steel, differing only in the outer coating: BCPZ – cold galvanized (silver), suitable for indoor use; BCPB – fully white coated (RAL 9010), for white cladding and frames; BCPN – black coated, for black profiles and components; BCPZ BL – a standard galvanized body but with the head alone painted white, for cost savings with an aesthetic white head.

When must I use BCP A2 (stainless steel) instead of BCP steel?

When fastening an aluminum profile in a humid, wet, or outdoor environment – you must use BCP A2 (SS304/A2 stainless steel). Using a standard steel screw in aluminum that will be exposed to moisture causes galvanic corrosion that will destroy both the connection and the profile. The BCP A2 is made of A2 stainless steel and comes with a passivation coating, ensuring no reaction with the aluminum.

Can the BCP A2 be used to drill steel?

No. The BCP A2 extra-flat head self-drilling screw is intended for use with aluminum only. Attempting to drill steel with a stainless steel screw will cause the drill point to burn out – because A2 stainless steel is not hard enough to penetrate steel. To drill steel under corrosive conditions, use ADIT’s bi-metal BIE models.

What is the maximum profile thickness that the BCP extra-flat head self-drilling screw can drill?

The BCP steel models (BCPZ/BCPB/BCPN) can drill a steel profile up to 4.4 mm thick. The BCP A2 (stainless steel) model is limited to a thickness of up to 2.0 mm (aluminum). Exceeding the maximum thickness will cause the drill point to break and the installation to fail.

Why does the screw’s drill point break?

The common causes of drill point breakage in an extra-flat head self-drilling screw: driving at an angle (not 90 degrees), driver speed too high, drilling a profile thicker than the maximum allowed for the model, or using BCP A2 on steel (not permitted). Using cheap screws from unapproved sources – in which the drill point steel is soft – is another common cause of failure.

What is the difference between failure load (Nrk), design load (Nrd), and recommended load (Nrec)?

The characteristic failure load (Nrk) is the value at which the screw fails in laboratory testing. The design load (Nrd) is the value engineers use for safe engineering design (after dividing by a safety factor). The recommended load (Nrec) is an even more conservative value for use in most construction applications. Never design according to the failure load! ADIT provides professionals with all the data required for a correct calculation.

What happens if I over-tighten the BCP extra-flat head self-drilling screw?

Over-tightening an extra-flat head self-drilling screw can cause “stripping” of the thread in the thin profile, reduced pull-out capacity, and deformation of the profile itself. The maximum tightening torque for ST 4.2 is 4.7 Nm. It is recommended to use a driver with a preset torque setting.

Fastening steel or aluminium profiles? Tell us the profile thickness, material and load – our engineers will select the right BCP model and send you the approved pull-out and shear data.

Talk to our engineers