Fabrication tools, machines and equipment are essential assets in various professional fields across Kenya, from county referral hospitals to educational institutions and agricultural cooperatives. Maintaining these assets in optimal condition ensures productivity, safety and cost efficiency. This chapter focuses on how to properly repair fabrication tools and implement preventive maintenance techniques that extend the operational life of welding and fabrication equipment.

3.1 Fabrication tools repair

Repairing fabrication tools promptly and correctly is crucial to prevent prolonged downtime and reduce the risk of accidents in a welding and fabrication workshop. Skilled repair enhances tool reliability and supports continuous operations in metal fabrication for maintenance and construction tasks.

Identifying common faults in fabrication tools

Beyond the faults of particular parts, powered fabrication tools also suffer general faults that affect performance. These include mechanical wear, electrical failures and misalignment.

• Mechanical wear: Shows as reduced cutting efficiency, rough running or unusual vibration during operation.
• Electrical failures: Faulty wiring or damaged switches cause intermittent power or complete tool failure.
• Misalignment: Parts that are out of line lead to poor weld quality or uneven cuts, which affects the final product.

Diagnosing and troubleshooting techniques

Effective diagnosis starts with visual inspection to detect visible damage such as cracks or corrosion on tool surfaces. Testing electrical continuity with a multimeter helps to identify wiring faults. Functional tests under controlled conditions reveal operational faults such as overheating or inconsistent performance. For example, a fabrication workshop that troubleshoots a faulty metal-cutting machine step by step, from the visible parts to the electrical parts, finds the fault faster and minimises downtime.

Repair procedures and safety precautions

Repair procedures vary with the fault but generally include disassembling the affected parts, replacing worn or damaged components, and reassembling with correct alignment. Safety precautions must include disconnecting power sources before maintenance, using appropriate personal protective equipment (PPE) and following the manufacturer's guidelines. For instance, a welding workshop can lock and tag the isolator of a machine under repair so that nobody switches it on by accident.

Documentation and reporting of repairs

Accurate repair records support asset management and future maintenance planning. A record should include the date of repair, the nature of the fault, the parts replaced and the technician's name. In a welding training workshop, repair logs help to track tool reliability and to schedule preventive maintenance. A tool that cannot be repaired safely should be tagged out of service and reported so that it is not returned to the rack by mistake.

3.1.1 Handles

A handle is the part of a tool that the user grips to transmit force and control. It must hold the working part firmly, fit the hand and resist shock, moisture and oil. A loose or split hammer handle can let the head fly off, so a welding workshop will withdraw such a hammer from use until it is repaired.

Common handle materials

• Hardwood: Used on hammers, chisels, files and mallets. It absorbs shock well and can be replaced cheaply, but it splits, dries out and rots if neglected.
• Fibreglass: Used on heavier hammers and sledgehammers. It resists moisture and absorbs vibration, but the surface can fray when struck or scorched by hot work.
• Tubular or solid steel: Used on spanners, clamps, bolt cutters and pipe wrenches. It is strong but can bend permanently if overloaded with an extension pipe.
• Rubber or plastic grips: Fitted over metal handles on pliers, snips and screwdrivers for comfort and insulation. They harden, crack or slide when worn or contaminated with oil.
• Cast or pressed handles: Found on vices, clamps and machine levers. They can crack at the neck or lose threads where they join the screw.

Common handle faults

• Loose head: The head moves on the handle because the wood has shrunk or the wedge has worked loose. This is the most dangerous handle fault because the head can detach during a blow, and a head that keeps moving also wears the eye of the head.
• Splits and cracks: Caused by overstriking, missed blows or drying out. A split near the head or at the grip means the handle must be replaced.
• Splintering: Rough, raised fibres on wooden handles can cut or blister the hand.
• Bending or twisting: Steel handles bend when overloaded, which changes the tool's alignment and strength.
• Worn or slippery grips: Rubber sleeves that are cracked, loose or soaked in oil reduce control, especially when hands are sweaty or gloved.
• Corrosion and burrs: Rust pits and sharp edges on metal handles weaken the handle and injure the user.

Tools for handle repair

Replacing a wooden hammer handle

1. Make sure the hammer is safe to work on and fix it in the vice by the head, with the broken handle pointing upwards or sideways.
2. Saw off the damaged handle close to the head so that only the part inside the eye remains.
3. Drive the remaining wood out through the top (wedge end) of the eye with a drift punch, working from the handle side, where the eye is narrower. If the wood is stubborn, drill several holes through it first.
4. Choose a new handle of the correct length and shape for the hammer. A handle for a 450 g hammer is typically around 300 mm long.
5. Shape the top of the new handle with a rasp until it enters the eye snugly, checking the head sits square to the handle.
6. Cut a saw slot in the top of the handle, along the long axis of the eye, to about two thirds of the eye depth, for the wedge.
7. Fit the head onto the handle, then tap the other end of the handle on a bench to seat the head fully.
8. Drive the wooden wedge into the saw slot so that the handle spreads and locks inside the eye, then drive a steel wedge in across it (diagonally) if the design requires it.
9. Saw off the protruding wood flush with the head, smooth the grip with abrasive paper and rub in a little linseed oil.
10. Test by checking that the head cannot be twisted by hand and then by striking a scrap block lightly before returning the hammer to service.

Repairing other handles

Replace cracked rubber grips rather than taping over them, because tape slips and hides damage. Straighten a bent steel handle only if it is lightly bent and the metal shows no crack; otherwise replace the tool. A loose handle on a clamp or vice should have its screw, pin or lock nut checked and tightened or replaced.

3.1.2 Heads

The head is the working end of a striking or shaping tool, such as the head of a hammer, chisel, punch or screwdriver. It is hardened to resist wear but is also brittle in places, so repeated misuse changes its shape. In a fabrication workshop, the team will regularly dress the heads of cold chisels because a mushroomed head can send sharp fragments flying.

Common head faults

• Mushrooming: The struck end of a chisel, punch or drift spreads outwards after repeated hammering. The thin lip that forms can break off at high speed and cause eye or skin injuries.
• Chipped or cracked face: A hammer face that is chipped, usually from striking a hardened surface or another hammer, may shed fragments.
• Rounded or worn face: A smooth, worn hammer face glances off the work and wastes effort.
• Blunt or deformed cutting edge: A chisel edge that is rounded, nicked or overheated no longer cuts cleanly.
• Worn screwdriver tip: A tip that is rounded or twisted slips out of the screw slot and damages the screw.

Tools for head repair

Dressing a mushroomed chisel head

1. Inspect the chisel and confirm that the shaft is straight and the cutting edge is not cracked. Discard it if it is cracked.
2. Put on goggles and check that the grinder wheel is sound and the tool rest is set close to the wheel.
3. Hold the chisel against the face of the wheel with light pressure, grinding the edge of the mushroom away.
4. Rotate the chisel so that a slight bevel forms around the entire head, which prevents a new lip forming.
5. Dip the chisel in water frequently, because overheating softens the steel and ruins its hardness.
6. Check that the head is flat, free of cracks and slightly chamfered, then wipe it clean.
7. If the cutting edge is also worn, regrind it at an angle of about 60° for general work on mild steel, cooling frequently, and check it with a protractor.

Repairing hammer and screwdriver heads

Light chips on a hammer face can be dressed with a file or grinder, taking off only enough metal to remove sharp edges. A hammer with a deeply cracked head must be scrapped because it cannot be repaired safely. Screwdriver tips can be reshaped on a grinder or file until the sides are parallel and the end square, keeping the metal cool. Avoid re-hardening tool heads unless the correct heat treatment process is known, because wrong treatment can make them dangerously brittle.

3.1.3 Jaws

Jaws are the gripping surfaces of vices, pliers, clamps, locking pliers and adjustable spanners. They hold work steady so that it can be cut, welded or tightened accurately. In a fabrication workshop, worn jaws on an adjustable spanner round off the corners of nuts, leaving the fitter unable to loosen them.

Common jaw faults

• Worn serrations: The teeth on the jaw faces become smooth so the tool slips on the work.
• Jaws not meeting parallel: Bent or sprung jaws touch only at one end, so work is held poorly or marked.
• Excess play: Loose pivots or worn adjusting screws allow the jaws to move sideways, as in an old adjustable spanner.
• Damaged screw or thread: A bent or stripped screw on a vice or G-clamp prevents the jaws closing under load.
• Cracked or chipped jaw plates: A crack across a vice jaw or clamp weakens it and the jaw may break under force.
• Weld spatter build-up: Hardened spatter on welding clamp jaws prevents good electrical contact and holds the work badly.

Tools for jaw repair

Replacing worn vice jaw plates

1. Open the vice jaws fully and clean away swarf, grease and spatter.
2. Remove the screws or bolts that hold the jaw plates to the vice body, noting how the plates are positioned.
3. Lift off the worn plates and check the seats for burrs or cracks. File off burrs, and do not continue if the vice body is cracked.
4. Fit the new plates with the serrated faces towards each other and fasten with the original screws.
5. Close the jaws gently and check that the plates meet evenly across the full width using a straight edge or by gripping a flat bar.
6. Lubricate the screw and slide and work the vice through its full travel to confirm smooth action.

Repairing pliers, clamps and spanners

Re-cut worn serrations on pliers with the corner of a triangular file, keeping the pattern even. Replace adjustable spanners and locking pliers with badly worn or sprung jaws because these slip under load and damage nuts. Adjust the tension screw on locking pliers so that the jaws lock firmly at the right opening. Clean spatter from welding clamp jaws with a wire brush and file, because poor contact can cause heating and unstable arcs.

3.1.4 Blades

Blades are the cutting edges of hacksaws, snips, shears, bolt cutters and guillotines. They cut by concentrating force along a thin hardened edge or row of teeth. In a fabrication workshop making steel gate frames, a blunt hacksaw blade makes cutting slow and the cut crooked, so the operator is tempted to press harder and risks breaking the blade.

Common blade faults

• Dull edge: The cutting edge rounds off with use, so more force is needed and the cut is rough.
• Missing or chipped teeth: Teeth break off when the saw is forced, twisted or used on hard material and can jam the cut.
• Bent or twisted blade: The blade wanders off the cutting line and may snap.
• Cracks or nicks: Small cracks in shear and guillotine blades spread and can lead to blade failure.
• Incorrect clearance: A gap between shear blades that is too wide folds or tears the metal instead of cutting it, and a gap that is too narrow makes the blades rub and wear quickly.
• Loose or corroded fixings: Blades that are not clamped firmly shift in use and chip.

Tools for blade repair

Replacing a hacksaw blade

1. Release the tension on the hacksaw frame by loosening the wing nut and remove the old blade from the pins.
2. Select a replacement blade of the right length and tooth pitch. Use finer teeth for thin sheet and tubing and coarser teeth for thick solid sections.
3. Fit the blade with the teeth pointing away from the handle, so that they cut on the forward stroke.
4. Tighten the wing nut until the blade is taut. Test by pressing it gently, as it should not bow or twist.
5. Check that the blade is straight and in line with the frame.
6. Make a few light cuts on scrap metal to check that the blade tracks straight before using it on the job.

Sharpening and adjusting shear blades

Remove the blades from the tool or secure them in a vice. File along the original cutting angle, using firm strokes in one direction only, until the nicks are removed and the edge is clean. Remove burrs from the back of the blade and wipe the edge with a fine stone. On guillotines and bench shears, set the clearance between blades according to the maker's instructions, because the correct gap depends on the thickness of material being cut. Test on scrap sheet and look for a clean, straight cut edge. Replace blades that are cracked, deeply chipped or too worn to sharpen.

3.1.5 Discs and wheels

Discs and wheels are abrasive or wire tools mounted on grinders and used for grinding, cutting, cleaning and finishing metal. They spin at high speed, so a worn or damaged disc can break and send fragments outwards. In a fabrication workshop, the technician checks the disc on an angle grinder before each job because a cracked disc can shatter while cutting steel bed frames.

Types of discs and wheels

• Grinding wheels: Thick abrasive wheels used on bench grinders to sharpen tools and shape metal.
• Cutting discs: Thin abrasive discs on angle grinders for cutting bar, pipe and sheet. They are not designed for side pressure.
• Flap discs: Overlapping abrasive flaps on a backing plate used for removing weld beads and blending surfaces.
• Wire wheels and cup brushes: Steel wire tools that remove rust, scale and slag.

Common faults

• Cracks and chips: Any crack, chip or damaged edge makes a disc unsafe and it must be discarded.
• Glazing: The abrasive surface becomes smooth and shiny so the wheel no longer cuts and the work overheats.
• Loading: Metal particles clog the face of the wheel and reduce cutting.
• Out-of-round or uneven wear: The wheel wobbles and vibrates, making ground surfaces uneven.
• Worn down diameter: A wheel worn small loses surface speed and may no longer fit the guard.
• Wrong speed rating: A disc rated for a lower speed than the machine's spindle speed can burst.
• Damaged wire brush: Loose or broken wires fly off and cause injury.

Tools for disc and wheel repair

Ring testing a grinding wheel

Tap a clean, dry vitrified wheel lightly with a non-metallic object such as a screwdriver handle, while the wheel hangs on a finger or pin. A sound wheel gives a clear ringing note, while a dull sound suggests a crack and the wheel must be discarded. Ring testing does not apply to thin resin-bonded cutting discs, which are examined by eye for damage.

Replacing a disc on an angle grinder

1. Switch off the grinder, unplug it from the supply and wait until the disc has stopped completely.
2. Check that the guard is in place and undamaged, because it protects the user if a disc breaks.
3. Press the spindle lock and loosen the retaining nut with the correct spanner.
4. Remove the nut and old disc and inspect the flanges for burrs, cracks or uneven seating.
5. Select a new disc of the correct diameter and bore, and confirm that its maximum speed rating is equal to or above the grinder's speed.
6. Place the disc on the spindle and make sure it sits flat against the inner flange.
7. Refit the nut and tighten it securely using the spindle lock.
8. Plug in, stand to one side and run the grinder freely for about a minute, in a safe direction, before starting work.

Dressing a bench grinder wheel

Wear goggles, set the tool rest close to the wheel and keep it only a small gap away, about 2 to 3 mm, so that work cannot be dragged between rest and wheel. Run the wheel up to full speed and pass the dresser across the face gently until the wheel is clean and true. Keep the wheel guard in place. Replace the wheel when it has worn so far that it can no longer be dressed to a true face.

Note on trolley castors

Wheels on welding trolleys are not abrasive tools, but they are repaired in a similar way. Clean and lubricate their bearings, replace worn tyres or axles and tighten loose fixings. Replace any castor with a cracked frame or a seized bearing, because it can fail under a heavy load such as a welding set with a gas cylinder.

Chapter Summary

This chapter provides a comprehensive overview of maintaining fabrication tools, machines, and equipment essential for welding and metalwork. It begins by detailing the repair of various components such as handles, heads, jaws, blades, and discs or wheels, emphasizing the importance of addressing wear and damage to ensure tool effectiveness. The chapter also covers cleaning the external surfaces of machines to prevent contamination and deterioration. Inspecting electrical elements like cables, connectors, and power sources is highlighted as crucial for safety and operational reliability. Lubrication of moving parts is explained as a key practice to reduce friction and extend equipment lifespan. Preventive maintenance strategies specific to welding fabrication tools and machines are outlined to avoid breakdowns and costly repairs. Finally, the chapter discusses the preparation of preventive maintenance reports, which serve to document maintenance activities and support ongoing equipment management.