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How to use Torx bits without rounding the screw

Updated: October 2026

The set is in the toolbox, and the screw is a star. How to use Torx bits is the sequence before the tool turns: the right T-number, a full seat, the driver square, and hammer mode off. Toolstation’s guide says the wrong size can damage the screw, and Accu defines cam-out as the bit twisting out once torque beats the bite. The [Torx bits comparison](/hub/drilling-and-accessories/torx-bits) lists the twelve sets. Choosing a shank is on the [Torx bit set buying guide](/hub/drilling-and-accessories/torx-bits/sub/torx-bits-buying-guide). The Products Compared editorial team wrote this from those UK sources on 15 October 2026. We did not run a lab test. A qualifying purchase can earn a commission at no extra cost to you.

The set is in the toolbox, and the screw is a star. How to use Torx bits is the sequence before the tool turns: the right T-number, a full seat, the driver square, and hammer mode off.

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Milwaukee Milwaukee Shockwave 32-piece set

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Wera Wera Bit-Check 30 TX Universal 1

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Wera Wera Bit-Check 30 TX Universal 1
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HORUSDY HORUSDY 14-piece tamper set

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HORUSDY HORUSDY 14-piece tamper set
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On this page
  1. 1.Seat the bit before the tool turns
  2. 2.Keep it square and let the clutch work
  3. 3.Hammer mode is not for screws
  4. 4.Stop, then decide who finishes the screw

Seat the bit before the tool turns

Pick the T-number on the packet. A T20 in a T25 recess sits on the lobe tips and rounds them. Push the bit in until the star is full and the tip bottoms. It should not rock if you tilt it before the drill starts. Electrical Safety First says seat the bit firmly and unplug a cabled screwdriver before you change the bit. A 1/4 inch hex bit should click in and survive a light pull. A magnet does not rescue a bad seat. The Gunpla bits here are 4 mm, and UK reviewers could not click them into a normal holder. If a pin stops the tip, stop, and do not grind it out.

Keep it square and let the clutch work

Hold the driver in line with the screw. A lean loads two lobes instead of six. On a drill-driver, start on a low clutch and a low speed, then raise the clutch only if it clicked before the screw was home. If the bit slips, stop. More speed polishes the recess. HSE’s INDG296, for people at work, says use the right tool and do not over-grip. A householder is not under PUWER. Eye protection still belongs on, because a climbing bit can throw a chip.
Milwaukee Milwaukee Shockwave 32-piece set

Testsieger

Milwaukee Milwaukee Shockwave 32-piece set
9.4/10about £17.90
View offer

Hammer mode is not for screws

Bosch DIY UK says not to leave the hammer function on when you do not need it. On the UniversalImpact 18V, screwdriving has its own symbol and a torque setting. Impact drilling is a different symbol, for masonry. Hammer mode pulses along the axis and knocks a Torx bit out of a screw. An impact driver’s blows are rotational. Use a bit the maker describes for that duty. Do not set a combi drill to hammer mode to imitate one.

Stop, then decide who finishes the screw

Cam-out ends the attempt with that bit. If the lobes are round, a fresh bit of the same size will spin. A hand driver gives you feel. A socket suits a bolt you can reach from the side. Call a professional for a seized brake, steering, suspension or seatbelt bolt, for an airbag or a high-voltage system, or if a bit has broken inside a structural bolt. For timber, stop if the bit slips.

Common questions

How do I know the bit is fully seated?
The lobes should fill the star, the tip should bottom, and the bit should not rock when you tilt it before the tool starts. In a 1/4 inch holder it should click and survive a light pull. A gap around the tip, or a 4 mm bit you are pinching with pliers, means it is not seated. Electrical Safety First says the same thing more shortly: seat the bit, then keep steady pressure. Unplug a cabled tool before you change the bit.
What do I do if the bit cams out?
Stop. Cam-out, as Accu describes it, is the bit climbing out of the recess. More trigger rounds the head. Check the T-number, reseat the bit, and hold the driver square on a lower clutch. If the lobes are already smooth, another bit of the same size will not bite. Use a hand driver only if some shape remains. Hammer mode makes a rounded head harder to remove.
Can I leave a combi drill in hammer mode to drive a Torx screw?
No. Bosch DIY UK tells you not to leave the hammer function on when you do not need it. The UniversalImpact manual gives screwdriving its own symbol and a torque ring. Impact drilling is the masonry symbol. Hammer mode moves the chuck along the screw, which loosens the seat and can mark the work. Turn the ring to the screw symbol and set a low clutch.
How is an impact driver’s blow different from hammer drilling?
An impact driver strikes in rotation. It can still destroy a Torx head if the torque exceeds the recess. Hammer drilling on a combi drill strikes along the axis so a masonry bit can chip brick. Using hammer mode to drive a screw copies the wrong blow. If you use an impact driver, fit a bit whose listing describes a shock or torsion zone, and stop at the first slip.
When do I stop and switch to a hand driver or a socket?
Switch when the power tool slips, when you cannot keep it square, or when you need feel on a tight screw. A hand driver suits a small or shallow head. A socket and ratchet suit a bolt you can reach from the side. Stop and fetch someone qualified for brake, steering, suspension, seatbelt, airbag, or high-voltage fasteners, and if a bit has snapped inside a structural bolt.
What if the screw has a pin and the bit will not go in?
The pin is blocking a solid tip. Do not file it off and do not drill it out. You need a bit with a hole in the same T-number. Mixed boxes often hide plain bits under a security title, so check the contents for an H or a stated hole. Once that bit is in the holder, the seat is the same: full lobes, square driver, low clutch, and stop if it slips.

Related pages

Security Torx vs standard Torx

Torx bits for impact drivers

Torx bits

Best Torx bit set: drill, impact, security or socket

Torx bit set buying guide: shank, the pin, then size

Sources

Public sources used for this comparison. Last checked on 16 October 2026.

  1. ISO 10664:2014 — hexalobular internal driving feature (retrieved 16 October 2026)
  2. BS EN ISO 10664:2014 — UK text of the recess standard (retrieved 16 October 2026)
  3. ISO 1173:2001 — assembly tools for screws and nuts, drive ends (retrieved 16 October 2026)
  4. Wera Impaktor TORX bits — impact geometry, not this Bit-Check (retrieved 16 October 2026)
  5. HSE — selecting powered equipment (PUWER) (retrieved 16 October 2026)
  6. Consumer Rights Act 2015 — GOV.UK (retrieved 16 October 2026)
  7. Insight Security — security Torx pin and matching bit (retrieved 16 October 2026)
  8. Camcar — TORX trademark and tamper-resistant family (retrieved 16 October 2026)