Drill spins but won't drive — chuck, clutch and gearbox

You squeeze the trigger, the motor groans up and spins, but the bit stands still — or the screw won't go in and the clutch starts clicking in mid-air before the screw has even seated. This is not an electronics fault. If the motor whines loudly but no torque reaches the chuck, the problem is almost always in the mechanical drive train: the chuck, the clutch, the gearbox or the hammer mechanism.

First, draw an important line. This article is about a tool whose motor runs but whose output spindle does not turn properly. If the motor doesn't come on at all — no sound, the trigger is silent, no reaction — that is a different world entirely (switch, carbon brushes, battery, broken wire). In that case read the piece on why a power tool won't turn on, not this one. Here we assume you can hear the motor spinning.

In Riga we most often see these drills and drivers around year four to six of use, when the clutch spring and the gearbox gears are already worn but the motor is still perfectly healthy. The battery platforms are good, it's a shame to bin them, and rarely does any of these faults call for a new tool.

Motor spins but the chuck won't turn — the gearbox

This is the clearest mechanical fault: you pull the trigger, the motor spins audibly and fast, but the chuck and bit stand still or turn far slower than the motor sounds. The motor rotates, yet torque does not reach the chuck — the chain between them is broken.

Inside the drill, between the motor and the chuck, sits a planetary gearbox: several stages with a sun gear, planet gears and their carrier. If the teeth on the sun gear or the planets have rounded off or snapped, the motor spins freely but does not drive the output. Another typical scenario — the planet carrier has cracked or its plastic has melted after prolonged overload; then the teeth are intact, but the carrier no longer holds the pins.

The signs that give it away:

• The motor spins loud and fast while the chuck stands still or twitches weakly.
• A cracking, knocking or metal-scraping noise comes from the gearbox housing.
• Torque intermittently "catches" and disappears again — partly broken teeth.
• Sometimes you smell hot plastic — a melted carrier.

Opening the gearbox, replacing the gear set and carrier, packing in fresh grease — that is a service centre job. The gearbox must not be packed with the wrong grease (ordinary general-purpose grease won't do here), and the planet pins must be seated precisely, or the same thing breaks within a week. There's no point taking it apart at home.

The chuck won't grip the bit, or the bit wobbles

Here the gearbox is fine — torque reaches the chuck — but the chuck itself fails to do its job. Inside a keyless chuck are three jaws that close on the bit's shank as you twist the sleeve. When the jaw teeth wear down or the mechanism clogs with metal swarf and dust, the chuck no longer grips.

Two different symptoms, two different nuances:

• The chuck won't grip the bit at all. You tighten the sleeve, but the bit pulls out freely or slips under load. The jaws are worn or dirty, the spring weakened.
• The bit wobbles / the drill runs in a "figure eight". The chuck grips, but the bit tip traces a circle — visible run-out. The culprit here is either the worn chuck itself or a worn spindle bearing the chuck sits on.

A simple test to tell the chuck from the bearing: insert a good, straight bit, tighten the chuck and slowly turn it by hand, watching the bit tip against a fixed reference point. If the chuck itself wobbles, replacing it is often enough. If the whole chuck assembly wobbles together with the spindle and you feel radial play when you push it sideways, you're dealing with the spindle bearing, which sits deeper, on the gearbox side.

Replacing the chuck is something many people can do at home on many models — more on that in the decision section and the FAQ. The spindle bearing is a service centre job.

The clutch slips — screws won't seat, clicks too early

Drivers have an adjustable clutch behind the chuck — the numbered ring that sets the torque at which the drive "disengages" with a click so you don't overdrive the screw. When the clutch starts slipping too early, you recognise it at once: you set the highest torque number or the drill mode, start driving a screw, and the clutch clicks in mid-air before the screw head has even touched the surface.

Inside is a clutch ring with teeth or balls and a spring that holds them together. Over time the spring tires and loses strength, or the clutch teeth/balls wear down. The result — the clutch "disengages" at far less torque than the number on the ring promises.

The last row is an important boundary. In drill mode (with the ring turned to the drill icon) the clutch is bypassed — torque goes straight through. If torque slips or vanishes even in this mode, the clutch is not to blame; the gearbox is. That's a good self-check before bringing the tool in.

Reviving the clutch means replacing the spring and clutch elements and reassembling precisely — done at the service centre alongside a gearbox inspection, since both assemblies sit in the same housing.

Hammer mode won't engage (on hammer drills)

A hammer drill (with the hammer/impact icon on the mode selector) has a separate hammer mechanism: two ridged (toothed) plates — ratchet discs — that clatter against each other when you press the bit into the material, giving the spindle small forward blows. That is what lets you drill into concrete and brick. If the mode is on but there are no blows — the bit just spins and skates over the concrete — these plates have worn smooth.

How to check reliably whether the hammer mechanism really is at fault:

1. Switch to hammer mode (the hammer icon).
2. Fit a bit, press it with noticeable force against a hard surface and run the revs.
3. Listen and feel: a healthy mechanism gives a noticeable, audible "rrrr" rumble and vibration. If there's only smooth rotation with no rumble, the blow is gone.

An important nuance: the hammer blow only appears under pressure. Many people think the mechanism is broken because nothing rattles in mid-air at no load — that's normal. The test is valid only with the bit pressed against the material.

Another common case in Riga flats — someone tries to drill a concrete wall with a light driver (no impact function) and wonders why it won't go. That's not a fault; such a tool simply has no hammer mechanism. Concrete needs a hammer drill or a rotary hammer.

Replacing the ratchet discs is a service centre job — the housing has to be opened, both plates replaced as a set and the hammer travel correctly adjusted.

The speed / mode selector is stuck

Some faults are not inside but on the surface: the selector is simply stuck or broken. Two selectors tend to cause trouble:

• The speed selector (1–2 gears) on top of the gearbox. If it's jammed between positions, the gearbox stays "in the middle" — the gears aren't fully engaged, and torque slips or doesn't get through at all. Often the only culprit is clogged mechanics or a slipped selector tab.
• The mode collar/ring (drill / screw / hammer) that won't click all the way into the position you need. Then the clutch stays partly engaged or the hammer partly disengaged.

What's safe to check at home: with the tool switched off (battery removed) move the selector by hand and push it fully into each position until it clicks. Never switch the speed selector while the motor is spinning — it's only moved on a stopped tool, or you'll wreck the gears. If torque returns after a proper full shift, the problem was just a partly engaged selector. If the selector is mushy, broken or won't move, it's an internal repair.

What you can fix yourself and what needs the service centre

The line here is clear: external, easily accessible parts — yourself; anything that needs the gearbox housing opened — the service centre. The key safety rule before anything: remove the battery (or unplug the mains cord) so the tool can't suddenly start.

Chuck replacement is the only "internal" job on this list that many people can genuinely do at home — more in the FAQ. The rest of the internals — the clutch, the gearbox, the hammer plates — are best left alone: there are loaded springs, precise assembly and grease choice in there, where one mistake means a repeat failure.

A practical note on whether it's worth repairing at all: professional-grade Makita, Bosch and DeWalt drills and drivers are durable, and a mechanical repair on them usually leaves you far ahead of an equivalent new tool. For a cheap unbranded drill with a burnt-out gearbox the picture may differ. We run a fast diagnostic and tell you honestly whether the repair is worth it, once we see exactly what's worn. If you're unsure which tool best stands up to daily load, our technicians will talk it through on site.

For more on what we do across the whole range of tools, see the page on power tool repair in Riga.