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I bought a Dewalt DCF900 impact driver. I've read their 2 sentence description of precision wrench mode, and still am not sure how to use it. Other than offering "greater control"...I'm not sure if it's safe to use this mode when fastening a nut.

What is the max torque when tightening in this mode? In an automotive setting, where can I safely use this mode? How does it prevent stripping the bolt when tightening? (I assume that's what the "precision" refers to).

(I asked Dewalt on their support/chat and got nothing but the same sentences cut and paste from their promotional material)

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The precision torque setting operates at max torque, which is 1030 ft-lb or 1396nm. About a minute into this video the feature is explained.

When tightening, precision wrench will spin at a lower than maximum RPM until it senses the movement stops, then pauses for just under a second before it starts impacting. The idea is that you can use it to drive nuts and bolts without impacting as the pause gives you time to let off the trigger. If you keep your finger on the trigger it will then impact at the maximum torque setting.

When loosening, precision wrench will go at full torque until is senses it break free, then it will slow the spin speed.

There's a decent summary of the features on this page.

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  • When you say "at your chosen torque setting" - which setting? The 1/2/3 settings are an alternative to Precision mode...so I don't understand what torque settings it is using
    – TSG
    Commented Mar 13 at 16:09
  • My understanding it that precision is independent of the torque setting, you can apply it or not, but I don't actually have one of these - I was thinking of upgrading as I have a previous model.
    – GdD
    Commented Mar 13 at 16:19
  • I've done a bit more research @TSG, and found someone who explains it.
    – GdD
    Commented Mar 14 at 14:51
  • I watched the video and it didn't really answer the core of the question. Similarly, the article doesn't address the core of the question. (The article looks like they just rewrote the marketing brochure). The spin before impact is clear, but any mechanic would want to know what is the torque setting it will use on tightening - or you will strip the threads out. Without more details I can't imagine anyone using this feature...too risky
    – TSG
    Commented Mar 15 at 16:47
  • It does explain it though @TSG, it operates full torque on that mode, which is 1396nm. I agree it's not a feature I would use though, if you don't get off the trigger fast enough you could cause a hell of a mess! I have the 899 and it's a great wrench, the variable torque setting is useful, and I have enough control on the variable trigger that I don't see the point of this precision feature.
    – GdD
    Commented Mar 15 at 17:07

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