Maintaining a rivet gun for reliable results

Why a little maintenance goes a long way

A rivet gun is one of those tools that gets pulled out of the drawer, used hard for ten minutes and put away without a second thought. That works fine for a while, then one day the mandrel slips through the jaws, the handle goes stiff, or a rivet sits half-set and refuses to pull. Almost every one of those faults traces back to dirt, dryness or worn jaws rather than a failed tool.

Ten minutes of care after a session is usually enough. Hand riveters, lazy tongs and pneumatic guns all reward the same basic routine: clean out the swarf, keep the working parts lightly oiled, and check the jaws before they start slipping rather than after. Do that and the tool pulls consistently, cycle after cycle, whether you are patching a sill on a classic car or building a trailer frame.

Know the parts that do the actual work

Before cleaning anything, it helps to know what you are looking after. On most guns the rivet mandrel passes through a nosepiece, then between two or three hardened jaw segments held in a tapered sleeve by a spring and a jaw pusher. When you squeeze the handles or trigger the air valve, the jaws grip the mandrel and pull it back, compressing the rivet body until the mandrel snaps at its break point.

Three areas take all the punishment:

• The jaws, which grip and release thousands of times and eventually lose their bite.
• The nosepiece, which centres the rivet and wears oval with heavy use.
• The jaw spring and pusher, which return the jaws to the open position between pulls.

Everything else — handles, body, air cylinder — rarely gives trouble if the working end is kept clean.

Cleaning after every session

Snapped mandrels are the main source of grit inside a gun. Most hand riveters collect the broken tails in a small bottle or tube; empty it before it fills, because a full collector forces debris back up into the jaw chamber. On pneumatic guns, unscrew the collector and tip the tails into the bin rather than the workshop floor.

Next, strip the front end. Unscrew the nosepiece and remove the jaw housing, then slide out the jaws, spring and pusher. Wipe each part with a clean rag. If there is dried grease or metal dust packed into the taper, soak the jaws in paraffin or a light solvent for a few minutes, agitate them, then dry thoroughly with compressed air or a lint-free cloth.

Two things to avoid: never file or grind the jaws to sharpen them, and never wash them in water-based degreaser without drying immediately afterwards. Both shorten their life considerably. Blow out the body of the gun too, especially on air tools, where dust migrates past the piston seal over time.

Lubrication without overdoing it

Riveting is a metal-on-metal job, so the jaws and the taper they sit in need a film of lubricant, not a bath. A single drop of light machine oil on the jaw assembly is plenty for a hand tool; too much and the oil traps metal dust and turns into a grinding paste.

Pneumatic guns need a different approach. Add a few drops of air tool oil into the inlet before each session, or fit an inline lubricator if you use the gun regularly. That oil protects the piston and seals, which is where most air riveters fail. Separately, keep a water trap or filter on the airline — moisture from a compressor is far more damaging to the internal mechanism than a little honest dirt.

For the handle pivot and linkage on lazy tong riveters, a spot of general-purpose grease on the pins keeps the action smooth and stops the handles binding halfway through a long pull.

Checking jaws and nosepieces for wear

Jaws are consumables. Expect to replace them eventually, and treat replacement as routine rather than a repair. The telltale signs are easy to spot: the mandrel slides through without gripping, the gun needs two or three squeezes to bite, or rivets set inconsistently with some proud and some flush.

Inspect the jaw teeth under a bright light. A light polish on the gripping faces is normal; flattened, chipped or rounded teeth are not. Replace the whole jaw set as a unit — mixing one new jaw with two worn ones gives uneven grip and chews mandrels. Fit the new jaws the right way round, with the tapered end facing the direction of pull, and refit the spring and pusher in the order they came out.

Nosepieces wear more slowly but matter just as much. If the bore has gone oval, rivets sit off-centre and set crookedly. Check that the nosepiece matches the rivet diameter you are using — 3.2 mm and 4.0 mm are the common sizes in the UK, with 4.8 mm for heavier work — and keep a spare of each on the shelf.

Storage and quick fault-finding

Store rivet guns somewhere dry, with the jaws left in the open position rather than clamped shut. Hang air tools on a hook if you can, and give the airline a blow-through before connecting. Lubricate the pin threads on interchangeable nosepieces so they do not seize.

When something does go wrong, work through the likely causes in order:

• Mandrel slips through: worn jaws, a weak spring, or a nose piece that is too large for the rivet.
• Rivet will not pull up: jaws jammed with debris, or a rivet body too short for the material thickness.
• Handles stiff or gritty: dry pivot pins or debris in the linkage.
• Air gun loses power: low pressure, blocked filter, or a dry piston seal.

Nine times out of ten, a clean, correctly oiled gun with fresh jaws pulls every rivet the same way. That consistency is what turns a frustrating job into a quick one — and it costs you almost nothing to maintain.