3 min to read
Centrofix
About
We outline creating a hybrid bit driver with high mechanical precision and bit stability by integrating the CentroFix bit holder into a high-tolerance handle. PB Swiss and Anex/Tamiya handles provide feasible platforms for mechanical adaptation. Two pathways: interference fit and cavity modification are viable depending on preferred handle characteristics and ratcheting requirements.
The Grail
A ratcheting bit driver with the following characteristics:
- near-zero play in the ratchet mechanism (rotationally and lock-up)
- low or ergonomically mitigated backdrag
- minimal axial and radial play in bit retention
This configuration does not currently exist as a single commercial product but can potentially be achieved by combining selected components from existing tools.
PB Swiss
Nice.
- Possibly the best ratchet mechanism in terms of lock-up and play
- But with high of back drag
- Available in SwissGrip (elastomer over polypropylene) and acetate handles
- Standard magnetic bit retention
- Magnets are strong, but axial and radial slop remains
- Bit holders are standard magnetic retention
- While they use strong magnets, since bits aren’t locked into place, there’s a typical amount of slop
- Ratchet handles are unlikley be able to accomodate a CentroFix bit holder
Anex
Specifically the Anex 397
- Ratcheting mechanism comparable to PB Swiss in play and lock-up
- Japanese ball-style grip provides ergonomic torque assistance, which helps mitigate the functional impact of backdrag
- Handle material is utilitarian (boring)
- Tamiya 74152 is a rebranded version with possible glass-fiber content
- Ratchet direction switch is superior to the Vessel 2200
- Deep bit holder
- 45mm insertion depth, so bits would have to be at least 65mm to fit
- Designed for Japanese blade-style driver bits
- Standard ISO 1173 C6.3 and E6.3 bits are too short
- Offers several possibilities to accommodate a CentroFix bit holder
- 45mm insertion depth, so bits would have to be at least 65mm to fit
Vessel
In comparison, the Vessel 2200 series has a similar form factor, but differs in that
- Convertable to a stubby
- Infuriating ratchet direction switch
- Average ratchet mechanism
CentroFix
Authorities on the matter (https://www.youtube.com/watch?v=vGDg27AjQR4) demonstrate
- Retention system based on four ball bearings engaging bit shank flats
- Minimal play, effectively behaves like a fixed-blade configuration
- Compatible with:
- C6.3 (25mm bits)
- E6.3 (power tool standard)
- JIS 13mm anvil bits (larger than standard 9mm)
- ‘Available’ in two formats:
- Standalone bit holder: exhibits eccentricity, not recommended for high-RPM use.
- Extraction (harvesting) of the CentroFix mechanism from integrated Wiha Centrofix drivers
Handling the Centrofix
The goal is to permanently install a CentroFix bit holder into a high-quality handle. The candidates are:
- Non rachetting: PB 8215.A (SwissGrip), PB 215.A (Acetate)
- Ratchetting: Anex 397, Tamiya 74152
Approach: interferance fit
PB Swiss 215 series handles fit proprietary PB Swiss blades which measure 6.2mm in diameter aside from the positioning wings. On the otherhand, a 1/4” hex shank bit measures 6.35mm accross the flat faces. The 0.15mm oversize results in a press-fit.
Insertion method:
- Chamfer the entry with a countersink bit to improve alignment
- Warm the handle (50–60 °C) to increase compliance.
- Insert the shank with a press to ensure axial alignment.
Approach: handle modification
