Impact Driver Not Driving Screws Properly? Here's What to Check

You're halfway through a job and your impact driver starts spinning screws instead of driving them. Or worse, it's chewing up screw heads and you're burning through bits. Before you chuck it in the van and buy a new one, let's work through what's actually going on.

The Most Common Cause: Wrong Bit for the Screw

I see this constantly on site. Someone's using a PH2 bit on Pozi screws, or vice versa. They look similar but they're not the same thing.

Here's how to tell: Pozi screws have small lines between the cross arms. Phillips don't. Using a Phillips bit on a Pozi screw will cam out and chew the head every single time. Get yourself a decent set of impact-rated bits with both types clearly marked.

Your Bits Are Worn Out

Impact driver bits take a hammering - literally. That impact mechanism delivers around 3,000 blows per minute. Even good bits wear down.

Hold your bit up to a new one. If the tip looks rounded or the edges are worn, that's your problem. A worn bit won't grip properly and you'll strip screws all day long. Replace bits regularly - they're cheap compared to the screws and time you'll waste.

The Torque Setting Issue

Some impact drivers like the DeWalt DCF887 have multiple speed and torque settings. If you're driving small screws into softwood and the driver's on full power, it'll overdrive them before you can lift your finger off the trigger.

For 4mm screws into timber, you want the lowest setting. For 6mm coach screws into hardwood, crank it up. Match the power to the job.

Battery Not Fully Charged

This catches people out. A battery showing two bars might have enough juice to spin the motor, but not enough grunt for the impact mechanism to work properly. The driver will turn but it won't deliver that hammering action that actually drives screws.

Stick a fresh battery on and see if the problem disappears. If you're running through batteries fast, they might be past their best - lithium cells degrade over time, especially if they've been left fully discharged or got too hot in a van.

Screw Quality Matters More Than You'd Think

Cheap screws from the bargain bin have soft heads that strip easily and inconsistent sizing that doesn't match standard bits properly. The few quid you save gets eaten up in wasted screws and time.

For anything structural or visible, use decent screws. Spax, Reisser, or Zip-R are all reliable. Your impact driver will suddenly work much better with screws that are actually made properly.

When It's Actually the Driver

If none of the above fixes it, the impact mechanism itself might be worn. The anvil and hammer inside take a beating over years of use. You'll usually hear a change in sound - less of a sharp impact, more of a grinding noise.

On a quality driver this shouldn't happen for years of daily use. If your driver's still under warranty, get it looked at. If not, it might be rebuild time or replacement time.

Quick Checklist

• Right bit type for the screw? (Pozi vs Phillips vs Torx)
• Bit in good condition?
• Appropriate torque setting?
• Battery fully charged?
• Decent quality screws?

Nine times out of ten, it's one of the first three. The tool's usually fine - it's the consumables that let you down.