No.4 (3mm) Pozi Countersunk Wood Screws DIN 7997 A2 Stainless

No.4 (3mm) pozi countersunk wood screws to DIN 7997, in A2 stainless steel. The head pulls flush with the surface in a countersunk hole, and the pozi recess takes a PZ1 bit.

A2 stainless resists rust outdoors, which makes these a good fit for cladding, garden projects and general joinery, inside or out. You can buy a single screw or a thousand with no minimum order, and the price breaks get better the more you buy.

What pozi countersunk screws are used for

Pozi countersunk screws are a general-purpose wood screw. The head pulls down flush, which makes them a common choice for fitting hinges, catches and other hardware. A power driver tends to slip out of a slot, but the pozi recess holds the bit well, and better than a Phillips head, so these drive cleanly with a drill driver.

If you are fixing into chipboard, MDF or other sheet board, our 3mm pozi countersunk chipboard screws are threaded along their whole length and have a sharp, self-cutting point.

Only the lower part is threaded, with a plain shank under the head. With a clearance hole in the top piece, the thread grips just the bottom piece and clamps the joint together.

Under the head is a 90° cone, which sits flush in a hole cut with a standard 90° countersink bit. US imperial flat head screws use an 82° head, so they won't sit exactly right in a 90° countersink.

Choosing a size

A bigger gauge number means a thicker screw. At 3mm across the thread, the No.4 is the smallest in this range, below the No.6 (3.5mm).

A countersunk screw is measured overall, from the top of the head to the point, since the whole screw finishes in the wood. You can choose from 6 No.4 lengths between 10mm and 30mm.

Expect a new No.4 to measure 3mm across the thread, or a fraction under, because 3mm is the nominal size. The shank below the head can be narrower, down to 2.6mm, and that's within the standard. You'll find both figures in the dimensions table.

Material: A2 stainless

These are A2 stainless, the everyday grade for fixings and part of the same family as 304 and 18/8. It handles rain and damp, which is why it's so widely used on outdoor timber. A2 is close to non-magnetic, so don't worry if a magnet pulls slightly.

For coastal or poolside jobs, A4 holds up better against salt. See our guides to A2 stainless steel and A4 stainless steel for the difference.

Pozi screw questions

What size is a No.4 screw in mm?

The thread on a No.4 is 3mm across. These are made to DIN 7997, which also sets the head: 5.6mm across and 1.65mm high at most, with a PZ1 pozi recess.

Gauge sizes come from imperial screws. Ours are metric, and a 3mm thread is the nearest match to an imperial No.4, which is about 2.8mm.

What bit do No.4 pozi screws need?

A PZ1 pozi bit. Pozi and Phillips heads look alike, but a pozi head has four small tick marks between the arms of the cross, and the bit has ribs to match.

A Phillips bit will turn a pozi screw, but it doesn't seat fully and tends to slip out as the screw tightens, which can damage the head. With the right bit, a pozi head takes more turning force before the bit slips.

If you'd rather use a flat-blade screwdriver, our No.4 slotted countersunk wood screws have the same head with a slot.

What is a No.4 x 1 inch screw in mm?

Go for 3 x 25mm, the nearest metric size. Every length is listed in inches and millimetres, for example 1/2in (12mm), 3/4in (20mm) and 1 1/4in (30mm), because plenty of people still think in inches. The screws are made to metric lengths, so a 1in screw here is 25mm rather than 25.4mm.

How do I measure a No.4 pozi screw?

Hold a caliper across the outside of the thread. A new No.4 reads 3mm or a touch under, because 3mm is the nominal size. DIN 7997 lets the plain shank below the head go down to 2.6mm, so treat that as a separate reading.

Length is measured overall, from the tip to the flat top of the head.