Tools & DIY · Head-to-head
CDI Torque Products 401SM Micro-Adjustable Torque Screwdriver vs Wiha 28418 SoftFinish TorqueVario-S 0.8 to 5.0 Nm
Which should you buy? Our verdict on both, pulled from our full The Best Torque Screwdrivers: 4 Compared (and One to Skip) comparison.
The 401SM is the one that behaves like an instrument: a cam-over clutch that releases rather than a click that asks you to stop, accuracy quoted as a percentage of the indicated value, and a serialized certificate traceable to NIST. The Wiha covers a wider and more metric-friendly band with the same plus or minus 6 percent and its own serialized certificate, and it is the better fit if your specs come in newton-metres.
CDI Torque Products 401SM Micro-Adjustable Torque Screwdriver
Buy itA cam-over clutch that disengages at the set torque, with accuracy stated as a percentage of the indicated value and a serialized certificate in the box.
- Cam-over torque limiting clutch: once it releases, continuing to turn does not pass more torque to the screw.
- Accuracy stated as plus or minus 6 percent of the indicated value, clockwise, which scales with your setting instead of being a fixed number.
- Individually serialized and supplied with a matching certificate of calibration traceable to NIST.
- Universal 1/4 inch hex bit holder with a rare earth magnet, so it takes ordinary insert bits rather than a proprietary blade.
- The accuracy claim is scoped to 20 to 100 percent of full scale, so nothing below 8 in-lb on this model is covered by it.
- Inch-pound scale only on the SM version; if your specs are metric you want the cN.m variant instead.
- CDI's own literature cites ASME B107.14M and ISO 6789, and ASME has since folded B107.14 into B107.300, so the cited edition is behind.
Wiha 28418 SoftFinish TorqueVario-S 0.8 to 5.0 Nm
Buy itA serialized, certificated adjustable driver covering 0.8 to 5.0 Nm with a 1/4 inch bit adapter, for people whose torque specs arrive in newton-metres.
- Plus or minus 6 percent accuracy tolerance, with a certificate of calibration and a laser calibrated scale marked and serialized for traceability.
- Wiha states the tool meets ASME B107.14m, EN ISO 6789 and BS EN 26789, which is more standards detail than most makers publish.
- Accuracy guaranteed to 5,000 cycles, which matches the default recalibration interval in ISO 6789-2:2017.
- 0.8 to 5.0 Nm is roughly 7 to 44 in-lb, a band that covers bicycle stems, optics rings and most small electrical terminals.
- It is a click type: it makes an audible and perceptible click and resets, but nothing stops you applying more torque after the click.
- The setting is changed with a separate adjustment tool rather than a knob, which suits a bench and not a jacket pocket.
- The scale is newton-metres only, so an inch-pound spec has to be converted before you set it.
Side by side
The 8 criteria below are the ones our full comparison judged every product on, narrowed to these two.
| CDI Torque Products 401SM Micro-Adjustable Torque Screwdriver Our pick | Wiha 28418 SoftFinish TorqueVario-S 0.8 to 5.0 Nm | |
|---|---|---|
| Our verdict | Buy | Buy |
| Best for | Anyone who wants a torque screwdriver that is a measuring instrument first, with a document tying its accuracy to a serial number. | Electronics, electrical and bicycle work where specs are quoted in newton-metres and you want a certificate with a serial number on it. |
| Price tier | $$$ · premium | $$ · mid-range |
| Limiting mechanism | Cam-over clutch, disengages at the setting | Click and reset, signals the setting |
| Torque range and steps | 5 to 40 in-lb, 0.5 in-lb increments | 0.8 to 5.0 Nm, about 7 to 44 in-lb |
| Stated accuracy | Plus or minus 6 percent of indicated value, clockwise | Plus or minus 6 percent |
| Range the accuracy claim covers | 20 to 100 percent of full scale | Not separately stated |
| Standards the maker cites | ASME B107.14M and ISO 6789 | ASME B107.14m, EN ISO 6789, BS EN 26789 |
| Calibration certificate | Serialized, traceable to NIST | Serialized, certificate included |
| Accuracy life claim | Not published | 5,000 cycles |
| Bit interface | 1/4 inch hex holder, rare earth magnet | 1/4 inch bit adapter plus Wiha blade system |
Which one is right for you?
Pick the CDI Torque Products 401SM Micro-Adjustable Torque Screwdriver if
anyone who wants a torque screwdriver that is a measuring instrument first, with a document tying its accuracy to a serial number.
Know before buying: the accuracy claim is scoped to 20 to 100 percent of full scale, so nothing below 8 in-lb on this model is covered by it.
Pick the Wiha 28418 SoftFinish TorqueVario-S 0.8 to 5.0 Nm if
electronics, electrical and bicycle work where specs are quoted in newton-metres and you want a certificate with a serial number on it.
Know before buying: it is a click type: it makes an audible and perceptible click and resets, but nothing stops you applying more torque after the click.
The bottom line
Our overall pick is the CDI Torque Products 401SM Micro-Adjustable Torque Screwdriver - A cam-over clutch that disengages at the set torque, with accuracy stated as a percentage of the indicated value and a serialized certificate in the box. Choose the Wiha 28418 SoftFinish TorqueVario-S 0.8 to 5.0 Nm instead if electronics, electrical and bicycle work where specs are quoted in newton-metres and you want a certificate with a serial number on it.
Want the full picture, including the other options we compared and the popular one we'd skip? Read the complete The Best Torque Screwdrivers: 4 Compared (and One to Skip).