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How to use an air impact wrench

Updated: 22 October 2026

You have just unboxed a pneumatic gun, the compressor is warm, and the anvil only clicks. That usually means dry vanes, a fitting that does not pass enough air, or a nut you are still driving after it has seated. This is how to use an air impact wrench for the first connection: oil, pressure at the tool, and when to stop. The [air impact driver comparison](/hub/tools/air-impact-driver) is the product table, not the procedure. Peter F. is the DIY & tools editor. The steps follow named UK guides plus review themes on those amazon.co.uk pages in October 2026. A qualifying purchase can earn a commission at no extra cost to you. If the fastener is safety-critical and you do not have the vehicle figure, stop and use a garage.

You have just unboxed a pneumatic gun, the compressor is warm, and the anvil only clicks. That usually means dry vanes, a fitting that does not pass enough air, or a nut you are still driving after it has seated.

Our top picks

BESWELL BESWELL BW-112BN

Best overall

BESWELL BESWELL BW-112BN
8.1/10about £39.99
View offer
Hilka Hilka 85151617 set

Alternative

Hilka Hilka 85151617 set
7.8/10about £41.99
View offer
Blue Spot Tools Blue Spot 07945

Best value

Blue Spot Tools Blue Spot 07945
6.8/10about £26.97
View offer
On this page
  1. 1.Before the hose goes on
  2. 2.Pressure, hose and fittings
  3. 3.Socket on, direction, and when to stop
  4. 4.If it still has no power

Before the hose goes on

Drain water from the compressor before you feed a tool. Moisture washes lubrication off the vanes and later shows up as a gun you cannot turn by hand. Chicago Pneumatic’s UK note treats two jobs as separate: air-motor oil through the inlet, or a filter-regulator-lubricator, and grease or an oil bath in the hammer. There is no single drop-count that every brand in this comparison agrees on. Use the sheet that came with your gun. Where that sheet is missing, the Clarke CAT141 manual is one published example, not a universal dose: a few drops of airline oil in the inlet before use and again every two or three hours, and do not exceed 90 psi at the tool while it is running. The Hilka 85151617 set lists a mini oiler, yet UK reviews say oil was missing and the grade was not explained. An ORAZIO review mentions a manual that asked for four drops. SAIC UK says solvent sprays such as WD-40 dry vanes and attack seals. Engine oil is not air-tool oil. Oil the inlet, then connect.

Pressure, hose and fittings

Set the regulator so the pressure at the tool, while it is running, matches that gun’s own sheet. For the Clarke example the ceiling is 90 psi, about 6.2 bar. The Hilka set recommends 90 psi. The Blue Spot states 90 psi and 4.5 CFM. Several other listings state nothing. The BESWELL pages also print ranges up to 190 psi, which is their claim, not a reason to wind your regulator up. The Health and Safety Executive’s compressed-air guidance is about injection injuries. Do not point an open airline at skin, and vent the hose before you disconnect it. Thread and bore cause as many dead guns as a weak motor. Where these listings state an inlet, it is usually 1/4 inch BSP. A UK review of the Blue Spot says the supplied inlet was smaller than the buyer’s other 1/4 inch fittings. An ORAZIO review says the manual asked for a 10 mm feed while the supplied fitting had a 6 mm passage. If the nipple does not match, the gun clicks and the gauge barely moves. Hose length is on the compressor page. A long, thin hose can starve a gun that is healthy on a short 3/8 inch line.
BESWELL BESWELL BW-112BN

Testsieger

BESWELL BESWELL BW-112BN
8.1/10about £39.99
View offer

Socket on, direction, and when to stop

Connect the hose and listen for a leak before you fit the socket. Then fit an impact socket, not a chrome hand socket, and set the direction. Reverse is for breaking the nut free. Forward is only for running a nut on until it seats. Keep the hose behind you so it cannot whip if a coupling lets go. Stop when the nut is loose. The hammer does not know a handbook figure, and these listings do not publish a torque for each regulator click. A review of the BESWELL BW-112K says the lowest forward setting snapped a Golf wheel stud, because those stage torques were not on the page. Extra impacts after the nut is home are how studs shear. For a suspension bolt you cannot find a torque for, a garage is the sensible stop.

If it still has no power

A rattle is often short air, not a dead motor on the first pull. Check that the tank was drained, that you oiled the inlet with air-tool oil, that the regulator holds the stated pressure while the trigger is held, and that the hose and nipple are the bore the gun expects. UK reviews of the bare Hilka describe a socket stopped by hand and a wheel nut that would not move, including one already loose. One Hilka-set review still had no power at 8 bar. Those accounts fit a starved airline as well as a weak gun, and neither Hilka states CFM, so the product page cannot separate them. If the fitting is correct, the compressor holds pressure on a short hose, and a free socket in the air still will not turn, use the returns route. Do not remove the regulator to add pressure. Oil and fittings look after a healthy tool. They do not turn a contradictory listing into a calibrated wrench.

Common questions

Where do I put the oil, and how often?
Put air-tool oil in the inlet, or use an airline lubricator. Grease in the hammer is a separate job, which is how Chicago Pneumatic splits the two. The Clarke CAT141 manual says a few drops before use and every two or three hours. An ORAZIO review mentions four drops. Follow your gun’s sheet. If it has none, treat Clarke as an example, not as a dose for every brand.
Can I use WD-40 or engine oil?
No. SAIC UK says solvent sprays such as WD-40 dry the vanes and attack seals. Engine oil is not air-tool oil. The Hilka set includes a mini oiler, but reviews say the grade was never stated. Buy a named air-tool oil, and use hammer grease only if the maker asks for it.
What pressure should I set?
Set pressure at the tool, while it is running, to that gun’s sheet. Clarke says do not exceed 90 psi at the tool for that model. The Hilka set recommends 90 psi and the Blue Spot states 90 psi. If your listing states nothing, do not guess upward. A BESWELL bullet that mentions 190 psi is that page’s claim, not a reason to ignore a 90 psi sheet on another gun.
Why does the gun only rattle?
Usual causes are a dry inlet, water in the tank, a nipple smaller than your other 1/4 inch fittings, or a hose that cannot pass the air. Blue Spot and ORAZIO reviews both describe undersized fittings. A free socket that will not spin, with pressure at the tool, points at the gun. A socket that spins freely but will not move a tight nut points at air volume.
What fitting thread is usual on these guns?
Where these listings state an inlet, it is 1/4 inch BSP. A stated thread is not a stated bore. One Blue Spot review found the inlet smaller than other 1/4 inch fittings. One ORAZIO review found a 6 mm passage against a 10 mm feed in the manual. Match the nipple you already use before you blame the hammer.
When should I stop on a seated nut?
Stop once the nut is free, or once a nut you are fitting has seated. These listings do not give a newton-metre value for each regulator click. Extra impacts after that are how studs shear. Finish critical fasteners with a torque wrench at the maker’s figure. If you do not have that figure, do not guess it on the trigger.

Related pages

Air impact wrench wheel nuts

Air impact wrench buying guide

Air impact driver

Best air impact wrench UK: a home garage shortlist

Compressor for a 1/2 inch air impact wrench at 90 psi

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars, review counts and specification lines are from the nine amazon.co.uk listings. Noise and vibration duties apply at work. They are not a certificate for a domestic gun, and no listing here was laboratory-tested.

  1. Control of Noise at Work Regulations 2005, regulation 4 (retrieved October 2026)
  2. HSE INDG362, Noise at work (retrieved October 2026)
  3. HSE, Hand-arm vibration regulations (retrieved October 2026)
  4. HSE HSG39, Compressed air safety (retrieved October 2026)
  5. ISO 11148-6:2012, Hand-held non-electric power tools, impact wrenches (retrieved October 2026)
  6. Homebuilding, Impact driver vs impact wrench (retrieved October 2026)
  7. Algar Air, Air tool consumption guide (retrieved October 2026)
  8. Ingersoll Rand safety information, via Cromwell (retrieved October 2026)