How to choose a bit set - profiles, hardness and drivers
A good bit set covers the common screw profiles and matches hardness and length to the job. This guide explains the key profiles (Torx, Phillips, hex), material hardness to DIN ISO 1173 and the difference between bits for cordless drivers and hand use.
View bit setsWhich bit profiles do I actually need?
Most fasteners in the workshop and electronics can be handled with a handful of profiles. The key is an exact match between bit and screw head, because the wrong profile or size leads to cam-out and damages both screw and bit.
Cross-head comes in two systems: Phillips (PH) and Pozidriv (PZ). They are not interchangeable, PZ has extra flanks for higher torque. Torx (star profile, TX/T) transfers torque almost radially and barely slips, which is why it dominates furniture, machinery and electronics today. Hex (Allen) holds reliably in grub screws and socket-head cap screws.
What matters for material and hardness?
Bits are made from alloyed tool steel (often S2, CRV or chrome-molybdenum) and hardened. The decisive factor is the balance between hardness and toughness: too hard means brittle and prone to breaking, too soft means the tip rounds off quickly.
Good bits sit at roughly 58 to 62 HRC. The dimensions and tolerances of the drives are set in DIN ISO 1173 (form C 6.3 for the 1/4" hex drive, form E 6.3). For hard screws and high torque, tough-elastic S2 bits are ideal; for impact drivers there are torsion-soft impact bits that absorb torque peaks through a torsion zone.
- S2 tool steel: high hardness and toughness, the standard for demanding fasteners.
- CRV (chrome-vanadium): robust and affordable, good for occasional hand use.
- Torsion zone: an elastic shaft absorbs torque peaks and extends service life.
- Diamond or TiN coating: more grip or better wear protection respectively.
Cordless or hand use - which bit fits?
The intended use dictates length, drive and hardness profile. For a hand screwdriver a short, precise tip counts; for cordless and impact drivers, length, magnetic holder and torsion behaviour are decisive.
- Hand use: short 25 mm bits with an ergonomic handle or bit holder, ideal for fine work.
- Cordless driver: 25 to 50 mm bits in a magnetic quick-change holder for fast swaps.
- Impact driver: use impact bits only, standard bits shatter under impact loads.
- Electronics and ESD: for sensitive assemblies pick dissipative handles and fine sizes (T6-T10, PH0).
Frequently asked questions
What is the difference between PH and PZ?
Phillips (PH) and Pozidriv (PZ) are two cross-head systems. PZ has extra flanks and transfers more torque without slipping. They are not interchangeable, the wrong combination rounds off both screw and bit.
What hardness should a good bit have?
Around 58 to 62 HRC. That is hard enough for long service life and tough enough not to break. For impact drivers you want torsion-soft impact bits.
Can I use standard bits in an impact driver?
No, impact bits are made for that. Standard hard bits shatter under the impact and torque peaks. Impact bits absorb these through a torsion zone.
Which bit length is right?
For hand use short 25 mm bits are enough. For cordless drivers 50 mm bits with a magnetic holder are practical, and longer versions help in deep bores.
Looking for the right bit set?
We supply bit sets and single bits in S2 and CRV steel - for Torx, cross-head and hex, for hand and cordless use.
Dimensionally true
Drives to DIN ISO 1173 with a play-free fit.
Robust hardness
S2 and CRV bits at 58-62 HRC for long life.
Impact range
Torsion-soft bits for cordless and impact drivers.
Expert advice
Our specialists help with profile and size.