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How to use SPAX screws: the bit, the pilot, the clamp

Updated: 22 October 2026

The box is open and the driver may not match the recess. How to use SPAX screws starts with that recess, not the slogan on the lid. A 4CUT point is a reason to try softwood and many boards without a pilot, and it is not a reason to skip a pilot in every timber. Which box to have bought is the [SPAX screws comparison](/hub/screws-and-accessories/spax-screws). Peter F., DIY & tools editor, wrote this from SPAX GB wording and the UK reviews, not from a workshop test, on 21 October 2026. A qualifying purchase can earn a commission at no extra cost to you.

The box is open and the driver may not match the recess. How to use SPAX screws starts with that recess, not the slogan on the lid.

Our top picks

SPAX SPAX A2 4 x 40 mm

Best overall

SPAX SPAX A2 4 x 40 mm
9.0/10about £20.02
View offer
SPAX SPAX YELLOX 4 x 30 mm

Best value

SPAX SPAX YELLOX 4 x 30 mm
8.6/10about £4.27
View offer
SPAX SPAX Pozi kit with bits

Alternative

SPAX SPAX Pozi kit with bits
6.6/10about £21.49
View offer
On this page
  1. 1.Put the matching bit in before the screw
  2. 2.Pilot when the wood is not the easy case
  3. 3.Clamp and countersink
  4. 4.When you stop

Put the matching bit in before the screw

Look at the recess before the trigger. Cross recess Z2, on the 4 x 30 mm and 4 x 50 mm YELLOX titles, is Pozidriv. The bit is PZ2. A Phillips bit cams out and rounds the head. Screwfix's screwdriver guide makes that distinction. A worn PZ2 does the same. Replace it. T-STAR plus is on the stainless A2 4 x 40 mm title, which says T20. That box does not include the bit. UK reviews report T15, a cross-head delivery, and a Torx 20 bit that was a tight fit. Try the bit in the screw you received. If it rocks, stop.

Pilot when the wood is not the easy case

SPAX says you can skip pre-drilling in softwood and in MDF, chipboard and OSB, depending on the wood. Hardwood, a knot or an edge still gets a pilot. None of these five boxes is a decking screw. One UK review used a 3 mm pilot and a countersink in 18 mm plywood. B&Q's gauge gives a 4 mm screw a pilot around 2.5 mm. Try it in scrap. Edges are on SPAX screws for chipboard.
SPAX SPAX A2 4 x 40 mm

Testsieger

SPAX SPAX A2 4 x 40 mm
9.0/10about £20.02
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Clamp and countersink

Full thread, on the 4 x 30 mm and 4 x 50 mm boxes, bites in both pieces. That suits a bracket into a stud. The thread in a top board can jack a gap. The clamp is a clearance hole in the top piece. Partial thread does that with a plain shank, and in this set that box is the stainless A2 4 x 40 mm. Drive square to the face. Wear eye protection, because a cam-out throws the bit. Keep loose gloves away from a spinning chuck.

When you stop

If you are also sawing, HSE limits are 3 mg/m³ for hardwood dust and 5 mg/m³ for softwood. Stop when no bit seats, when the timber splits, or when the joint is load-bearing and unspecified. Yellow zinc in the rain is the wrong product. That choice is SPAX stainless or yellow zinc.

Common questions

Which bit fits Z2?
A Pozidriv PZ2 bit fits a Z2 cross. Seat it so the bit does not rock. The 4 x 30 mm and 4 x 50 mm YELLOX titles are that recess. A worn PZ2 still cams out, because the rounded tip no longer fills the flanks, so the number on the shank is not enough if the tip is blunt.
Will a Phillips bit do?
No. Phillips and Pozidriv are different crosses. A Phillips bit in a Z2 head cams out and rounds the recess, and you then cannot finish that screw with the correct bit either. Borrow or buy a PZ2 rather than forcing the joint with the driver that happens to be in the drill.
Does T-STAR plus need SPAX's own bit, and what if the title says T20?
T-STAR plus is the star with a pin, and SPAX describes a matching bit. The A2 box here is titled T20 and does not include one. UK reviews report a T15 head, a cross-head delivery, and a Torx 20 bit that was tight and not magnetic. Try the bit in the screw you received. If it does not seat, do not lean on the drill.
When can you skip the pilot?
You can try without a pilot in softwood and in chipboard, MDF and OSB when the wood is the easy case SPAX allows, and you stop if it starts to split. Hardwood, an edge, and any joint you cannot afford to burst still get a pilot. A UK plywood review used 3 mm and a countersink in 18 mm. The wood in front of you decides, not the 4CUT line alone.
Why does the joint gap open when you tighten?
The thread is biting the top piece and lifting it. That happens with a full-thread screw through two boards. Drill a clearance hole in the top piece, or use a partial-thread screw whose shank can slide. Tightening harder makes the gap worse. The 30 mm and 50 mm boxes here are full thread. The 4 x 40 mm A2 box is partial thread.
What should you wear, and when does dust become an HSE matter?
Wear eye protection, because a cam-out throws the bit. Keep loose gloves out of the chuck. Wood-dust limits apply when you cut or sand, not when you only drive a screw. HSE gives hardwood a workplace exposure limit of 3 mg/m³ and softwood 5 mg/m³. If the job includes a saw, extraction belongs with the saw.
When do you stop and call a joiner or a designer?
Stop when the fixing carries a load that a drawing or a structural specification should own. Stop when the recess matches no bit you can seat. A carcass or a loft board you are allowed to fix can stay on this page. A yellow screw about to live in the rain should be swapped for stainless before you call anyone, because the coating is the wrong product.

Related pages

Best SPAX screws

SPAX screws

SPAX screws buying guide: finish, thread, then bit

SPAX screws for chipboard: 30 mm, 50 mm, or SPAX-M

SPAX stainless or yellow zinc: which screw outside

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are the amazon.co.uk lines in the display file. There is no laboratory test, no salt-spray test, and no pull-out value. A yellow assortment is not treated as ETA-12/0114.

  1. SPAX universal screw, WIROX page (retrieved 22 October 2026)
  2. SPAX technical lexicon (retrieved 22 October 2026)
  3. SPAX stainless A2 universal (retrieved 22 October 2026)
  4. SPAX UKCA (retrieved 22 October 2026)
  5. ETA-12/0114 (15 October 2024) (retrieved 22 October 2026)
  6. GOV.UK construction products (retrieved 22 October 2026)
  7. HSE wood dust (retrieved 22 October 2026)
  8. Screwfix screws buying guide (retrieved 22 October 2026)