Bit Holders and Ratchets
Screwdrivers and Bits
Bit holders take bits with a hex shank and transfer torque from handle, ratchet or extension to the screw; ratchets work with 1/4, 3/8 and 1/2 inch square drives. The key selection criterion for a ratchet is the number of teeth, because it defines the return angle and therefore the smallest swing needed to turn further: 72 teeth correspond to 5 degrees, 52 teeth to roughly 6.9 degrees and 44 teeth to roughly 8.2 degrees. Flat designs and slim heads from 23 x 12 mm are made for work between assemblies, while rotating grip and swivel head versions serve poorly accessible fastenings. The category holds 194 items, the leading brands are Wera, Wiha and Proxxon.
| Drive | Teeth | Return angle | Design |
|---|---|---|---|
| 1/4 inch | 72 | 5 degrees | stubby ratchet and micro head |
| 1/4 inch | 52 | roughly 6.9 degrees | standard ratchet, also with swivel head |
| 1/4 inch | 44 | roughly 8.2 degrees | extra flat design |
| 3/8 inch | 72 | 5 degrees | stubby ratchet with reversing lever |
| 1/2 inch | 60 | 6 degrees | swivel ratchet, length 430 mm |
| 1/2 inch | 52 | roughly 6.9 degrees | standard ratchet for higher torque |
Typical applications: Fastenings between densely populated assemblies using a micro head; assembly of control cabinets and machine panelling; maintenance with limited swing using fine toothed ratchets; series driving with a bit holder and magnetic seat; overhead work with a spring sleeve against dropping bits; maintenance on plant with mixed socket and bit drives.
