DIN 7982 Chipboard Screws: Countersunk Specs

Two words in that title disagree with each other, and the disagreement is worth understanding before an order is placed.

DIN 7982 is a German dimensional standard for a cross recessed countersunk head tapping screw — a screw whose thread forms its own path, and whose head is shaped to sit flush in a countersink. "Chipboard" names a board: a mat of wood chips and resin. The standard describes the screw's geometry. It says nothing at all about the material the screw is driven into.

That is not pedantry. It has a direct commercial consequence. When a purchase order says "DIN 7982 chipboard screw", the number has settled the head diameter, the head height, the core diameter and the diameter ladder — and has left the steel, the surface treatment, the point form and the coating performance entirely open. Different suppliers fill those gaps differently, and two cartons that both answer to "DIN 7982" can contain parts that are not interchangeable at the drawing level.

This guide reads the standard the way a buyer has to: what the number fixes, what it leaves open, what the real dimensional envelope looks like at each size, why the size ladder DIN uses is not the ladder the board trade uses, and what has to be added to a purchase order before "DIN 7982" describes a screw rather than a shape.

A note on the data. Every dimensional figure below is taken from our own published item data for the screws named — the DIN 7982 countersunk item, its JIS counterpart, and our reinforced-head board screw — rather than from a secondary summary of the standard. Where the three disagree, the disagreement is the point.

Chipboard and panel screws for furniture assembly

What DIN 7982 Actually Fixes — and What It Leaves Open

A standard is a document with a scope, and DIN 7982's scope is geometry. It is worth separating the columns, because buyers treat the whole specification as though the number carried it.

Read the bottom four rows together. They are the four things a furniture producer actually argues about, and none of them is in the standard. The number guarantees that the screw will fit a countersink cut to the standard's head dimensions, and that it will share tooling with any other screw of the same designation. It does not guarantee that the screw is hard enough to cut the material in front of it, that it will still be holding in three years, or that it belongs in the joint at all.

The practical form of this: DIN 7982 is a fit specification, not a performance specification. It answers "will this head sit flush in my countersink, and will my driver engage it". It does not answer "will this screw hold in my board".

The Dimensional Envelope, Size by Size

This is the envelope our DIN 7982 countersunk item is built to: nominal diameter d, core diameter d1, head diameter dk, head height k.

Three ratios run through that table, and all three are worth memorising, because they turn a catalogue into a calculation.

The core ratio decides whether the joint holds. A tapping screw cuts its own thread, so the pilot hole is not a clearance hole — it is the hole the thread is allowed to cut into. Our core diameter at 4.2mm nominal is 3.10mm, which is 74% of nominal. Drill the pilot at 3.1mm and the screw cuts a full thread with the material it displaces. Drill it at 3.5mm and the screw has almost nothing left to cut: it will drive easily, feel tight, and strip at a fraction of its intended torque. The ratio 0.74 is not a tolerance; it is the shape of the tool.

The head ratios give you the countersink. At 4.2mm nominal the countersink has to be 8.1mm across and 2.5mm deep for the head to seat flush. Those are the two numbers a countersink tool has to produce, and they decide whether the head ends up flush or proud in a thin panel.

Our DIN 7982 countersunk item and its full size table

The Naming Problem: Three Ladders, One Screw Type

Here is the part of the standard that causes the most trouble in practice, and it has nothing to do with how the screw is designed. It is the size ladder.

The three cross recessed countersunk screws we sell — the DIN 7982 item, its JIS counterpart, and our reinforced-head board screw — belong to three different diameter series. Only one size appears in all three.

There is no 4mm screw in the DIN ladder. The DIN series steps from 3.5 to 4.2; the JIS series and the board trade both step from 3.5 to 4.0. So an instruction that says "4mm countersunk self-tapping" is unambiguous in Japan and in the board trade, and ambiguous in the DIN world, where the nearest nominals are 3.5mm and 4.2mm and neither of them is 4mm.

This is why "just convert it" does not work. A 4.0mm JIS screw and a 4.2mm DIN screw are close enough to look interchangeable and different enough to matter. The head is 8.0mm against 8.1mm, so the countersink is nearly the same, but the core diameter — and therefore the pilot hole — differs, and a joint designed around a 4.0mm JIS screw has a different withdrawal strength with a 4.2mm DIN screw in it. Where a drawing specifies a diameter, the standard is part of the diameter.

The rule that follows: when a drawing or a legacy part number gives a diameter without a standard, establish which ladder the number came from before quoting. On the three ladders above, 3.5mm is the only safe assumption.

Self-tapping screws across the DIN and JIS ladders

Countersunk Heads at the Same Nominal: The Depth Is Not the Same

Even where the ladders meet, the heads do not match. Compare the countersunk head at 3.5mm nominal across the same three items.

The widths agree to within 0.2mm and the heights do not. The board screw's head is 7.0mm across — 0.2mm wider than both metal-tapping heads — and 1.65mm tall, which is 21% shallower than the DIN head's 2.1mm.

That difference is not cosmetic. Head height is the countersink depth the screw demands for a flush seat. In an 18mm panel a 3.5mm DIN screw needs 2.1mm of material removed and leaves 15.9mm; the board screw needs 1.65mm and leaves 16.35mm.

In an 18mm panel that 0.45mm is a rounding difference. In a 12mm panel, where the joint is already marginal, it is the difference between a countersink that holds and one that breaks through the visible face.

The shallower head is not an economy. The board screw carries R1.8 ribs under the head: a ring of cutting ridges that seats itself in the board and acts as a captive washer. That is why it can afford a flatter head — it cuts its own seat rather than relying on a machined countersink. The DIN 7982 head publishes no rib data at all, because in sheet metal the sheet itself provides the seat.

What to take from this: a countersunk head's height is a material-removal budget. Two screws with the same head diameter can demand different countersink depths, and the one that demands less is the one to use where the panel is thin or the face is visible.

DIN 267 and the Delivery Conditions the Number Omits

If DIN 7982 is the geometry, something has to carry the rest. In the German system that is the technical delivery conditions family, and DIN 267 is the number that appears alongside screw designations for exactly this reason.

We supply a semi-countersunk cross recessed item under DIN 267. Its published data is thin beside the 7982 item: one drive size, two lengths, a nickel-chrome finish. That thinness is informative. A delivery-conditions designation does not need a full size table, because the sizes come from the product standard; it needs to state what the product standard leaves out.

The useful reading: a designation such as DIN 7981 C-Z is a chain, and each element answers one question.

Where the chain stops is where your order starts. The chain above does not state the steel grade, the hardness, the salt spray hours, the dimensional tolerances, or the acceptance sampling. Those live in the delivery conditions and the certificate — and if your order does not name them, they are whatever the supplier's default happens to be.

Where a board joint needs a purpose-made screw rather than a tapping screw

Surface Finishes and What the Standard Says About Them

Nothing. The standard is silent on the finish, which is why the finish has to be written on the order. These are the four our DIN 7982 item is offered in.

Two distinctions decide whether a coating survives.

First, sacrificial versus barrier. Zinc coatings protect steel sacrificially: where the coating is scratched, the zinc around the scratch corrodes instead of the steel, so a cut in a zinc coating does not immediately become a rust point. Nickel-chrome is a barrier coating — hard, and correct-looking, but where it is breached, the steel underneath corrodes with no protection from its neighbours. Every screw gets scratched on the way in. That favours zinc in a corroding environment and nickel-chrome on surfaces that are seen and dry.

Second, the hours are not in the name. A zinc coating's performance is measured in a salt spray test to ISO 9227, and the hours vary enormously with the passivate and the coating thickness. Our Ruspert-coated board screw is published at approximately 500 to 1,500 salt spray hours, which is a coastal specification. A blue-zinc finish is not in that class, and the difference is invisible if the order says only "zinc plated".

Where a coating is the wrong answer and the screw has to be stainless

Writing DIN 7982 on a Purchase Order

Every line below is something the standard does not settle. A purchase order that names only the standard has left ten decisions to the supplier.

Item 10 is the one that catches buyers out. Where the drawing says "4.2 self-tapping countersunk, DIN 7982" and the supplier is out of stock, the natural substitution is a 4.0mm JIS screw — a different diameter on a different ladder. Writing the substitution rule into the order is the difference between a controlled change and an undocumented one.

Send us the drawing and the joint details for a dimensional check

Incoming Inspection: What to Measure

A DIN number on a carton is a declaration. Five measurements turn it into evidence, and all five are on the drawing.

The head height check finds the real defects. A head over the k value will not seat flush and stands proud by the excess; a head under it sits below the surface and leaves the countersink partly empty, which reads in service as a loose joint. The recess check matters on a powered line, where a shallow or off-centre recess strips heads by the hundred before anyone suspects the screws.

Common Specification Errors

Conclusion

DIN 7982 is a good standard and a narrow one. It fixes the head diameter, the head height, the countersunk angle, the core diameter and the diameter ladder of a cross recessed countersunk tapping screw. Everything a furniture producer actually argues about — the steel, the hardness, the coating, the salt spray hours, the pilot hole, the torque, and above all the material the screw goes into — sits outside it.

Read that way, the number becomes useful rather than decorative. It tells you the screw will fit a countersink and a driver. It tells you which ladder the diameter came from, which matters more than most buyers expect, because the DIN, JIS and board ladders agree at exactly one size. And it tells you the countersink depth the head will demand — the figure that decides whether a thin panel survives.

Key takeaways:

Special and non-standard fasteners to specification

Additional Resources

• Chipboard and Panel Screws
• Self-Tapping Screws, DIN and JIS
• Stainless Steel Screws, A2 and A4
• Standards and Drawing Support
• ISO 9001 Manufacturing

About Shaxi Hardware

With over 15 years of experience manufacturing furniture hardware and fasteners, Shaxi Hardware serves furniture and cabinet producers across 40+ countries. Our ISO 9001 certified production facility manufactures cross recessed countersunk and pan head tapping screws to DIN 7981 and DIN 7982, JIS cross recessed screws, reinforced-head board screws, confirmat and Euro screws, threaded inserts and stainless fasteners, in case-hardened carbon steel, brass and A2/A4 stainless steel, with blue and rainbow trivalent zinc, nickel-chrome, black and Ruspert finishes. Corrosion performance is tested to ISO 9227 with EN 1670 grading, dimensional and material certificates are issued per batch, and pilot-hole and torque data is supplied with each fastener family. Custom lengths, thread forms, head forms and coatings are available through our OEM engineering service.

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