Short answer: pick an air shut-off screwdriver when every screw has to reach the same torque, as in electronics, instruments and appliance assembly. Pick an air impact screwdriver when you need fast, high-force driving and removal and exact torque isn't critical, as in maintenance, automotive and general fabrication.
What is an air shut-off screwdriver?
An air shut-off screwdriver (also called a shut-off clutch or torque control air screwdriver) has an adjustable clutch. When the screw reaches the preset torque, the clutch cuts the air supply and the motor stops. The tool cannot keep turning, so the screw is not over-tightened, threads are not stripped, and the next screw gets the same torque.
Soartec's torque control models, such as the WX-3511 and WX-3502, are rated for ±3% torque accuracy at 90 psi.
What is an air impact screwdriver?
An air impact screwdriver uses a hammer mechanism that delivers rapid rotational blows. This gives it more breakaway force for driving long screws or freeing seized fasteners. Final torque depends on how long the operator holds the trigger, so it varies from screw to screw. The WS-305 1/4" pistol-type air impact screwdriver is a typical example.
Shut-off vs impact: key differences
| Air shut-off screwdriver | Air impact screwdriver | |
|---|---|---|
| How it stops | Clutch cuts air at preset torque | Operator releases trigger |
| Torque repeatability | High (±3% on Soartec torque control models) | Low; varies with operator |
| Typical torque | Low to medium (0.2–4.3 Nm across the WX-35xx range) | Higher; good for removal |
| Vibration and noise | Low | Higher (hammer blows) |
| Best for | Production lines, electronics, instruments, appliances | Maintenance, automotive, general fabrication |
Which air shut-off screwdriver fits my screw size?
Match the torque range to the screw. Rated values from Soartec's current line-up:
- Micro screws up to 2 mm: WX-3541, 0.2–0.35 Nm, 2,550 rpm, 0.25 kg, touch-start. Suits PCBs, phones and small electronics.
- Screws up to 3.5 mm: WX-3511, 0.9–1.6 Nm, 1,450 rpm, trigger start, with a suspension ring for balancer use.
- Screws up to 4 mm: WX-3534, 1.7–2.8 Nm, 1,200 rpm, 1/4" hex, magnetic bit holder, rear exhaust.
- Screws up to 5 mm in tight spots: WX-3502 angle head, 2.2–4.3 Nm, 800 rpm.
To narrow it down, choose a model whose target torque sits in the middle of its range rather than at either end. The clutch is most consistent there.
Push-start, trigger-start or touch-start: what's the difference?
- Trigger-start: the operator pulls a trigger. Gives the most control over when the bit turns.
- Push-start: the motor starts when the bit is pressed onto the screw, so there is no trigger to squeeze. This reduces finger fatigue in high-volume work. See the WX-3924 push-start screwdriver.
- Touch-start: starts on light contact. Common on compact models such as the WX-3534 and WX-3541.
When is an impact screwdriver the better choice?
- Removing rusted or over-tightened screws
- Driving long self-tapping screws into sheet metal
- Maintenance and repair work where speed matters more than exact torque
Frequently asked questions
Does an air shut-off screwdriver need a special air supply?
Soartec's WX-35xx models are rated at 90 psi. Use clean, dry, regulated air. Unstable pressure affects how consistently the clutch shuts off.
Can a shut-off screwdriver loosen screws?
Yes. The WX-35xx models have a forward/reverse switch with a lock, so you can reverse without holding the button down.
Why hang the tool on a spring balancer?
A balancer takes the weight off the operator's hand and keeps the tool from being knocked off the bench. Models like the WX-3511 have a built-in suspension ring for this.
Is an air shut-off screwdriver the same as a nutrunner?
They work the same way, but nutrunners are built for higher torque on nuts and bolts, usually with a square drive. For bolting, see Soartec's air shut-off nutrunners.
Find the right Soartec air screwdriver
Browse the full Soartec® air screwdriver range. For help matching torque, speed and start type to your production line, contact the Soartec engineering team.
