Stihl TS420 350mm (14") Petrol Cut-Off Saw - 3.2kW 66.7cc Two-Stroke

Who is this for

The Stihl TS420 is used by groundworkers, civils contractors, road construction operatives, drainage teams, and kerb and slab layers who require a handheld petrol cut-off saw capable of sustained cutting through concrete, asphalt, stone, and masonry on UK construction and civil engineering sites. The 3.2kW 66.7cc engine and 125mm maximum cutting depth cover the full range of kerb cutting, slab trimming, road reinstatement, expansion joint cutting, and pipe preparation tasks encountered in daily groundwork and civils operations. The compact design and 9.6kg weight make it practical for handheld use in trench bottoms, alongside kerb lines, and in confined working areas where larger floor saws cannot be manoeuvred. Health and safety officers and site managers responsible for COSHH compliance will note the integrated dosable water connection provides the on-tool dust suppression required by HSE guidance on respirable crystalline silica (RCS) when cutting concrete, stone, and masonry materials.

Typical applications

• Cutting kerbs, concrete edging, and paving slabs to length during road construction, reinstatement, and hard landscaping works where a precise straight cut is required on site.

• Road reinstatement cutting to define clean saw-cut edges around carriageway repairs, utility reinstatements, and pothole patching operations in compliance with the Specification for the Reinstatement of Openings in Highways (SROH).

• Cutting expansion joints in concrete slabs, hardstanding, and floor construction where a controlled straight cut to a specified depth is required.

• Cutting concrete and clay drainage pipes to length during drainage installation, connection, and repair works on groundwork and civils projects.

• Cutting ductile iron pipes, valve chambers, and utility apparatus during utility diversion and connection works on infrastructure projects.

• Concrete and masonry cutting during demolition and structural alteration works where a controlled cut to a specified line is required alongside or beneath existing structure.

• Cutting stone, yorkstone, and natural stone paving to shape and length during hard landscaping and public realm works where precision cut quality is a specification requirement.

• Asphalt cutting for road marking preparation, gully and drainage channel installation, and utility trench reinstatement on highways maintenance contracts.

How to use

Step 1: Before starting, inspect the cutting wheel for cracks, chips, buckling, or damage to the spindle hole. Never use a damaged cutting wheel. Confirm the cutting wheel is rated for the material to be cut and that its maximum permissible speed equals or exceeds 4,880rpm.

Step 2: For diamond cutting wheels, confirm the direction of rotation arrow on the wheel matches the direction of blade travel. Position the front thrust washer and tighten the hexagon bolt to 30Nm using the combination wrench supplied. Block the shaft with the locking pin through the V-belt guard bore whilst tightening.

Step 3: Check the fuel level. The TS420 runs on a 50:1 petrol to two-stroke oil mix. Fill using an approved fuel canister in a well-ventilated area at least 3 metres from the cutting location. Never refuel a hot engine.

Step 4: For wet cutting operations, connect a water supply to the dosable water connection on the machine before starting. Diamond cutting wheels must always be used with water. Ensure a minimum supply of 0.6 litres per minute for dust binding and blade cooling.

Step 5: To start a cold engine, press the decompression valve button, actuate the manual fuel primer pump 7 to 10 times, set the choke to the cold position, and pull the starter cord briskly. Once the engine fires, return the choke to the warm position and allow the engine to warm up before beginning cutting.

Step 6: Hold the machine firmly with both hands throughout the cut. Keep the right hand on the rear handle at all times. Guide the cutting wheel into the workpiece using the weight of the machine rather than pressing down. Never exert lateral pressure on the cutting wheel.

Step 7: At the end of each shift, drain the fuel tank if the machine will be stored for more than 30 days. Run the engine at idle until it stops to clear fuel from the carburettor. Remove the cutting wheel before storing. Clean the machine and store in a dry, secure location.

Common mistakes

Using the wrong cutting wheel for the material: A composite resin abrasive wheel rated for general purpose cutting will wear rapidly and cut poorly in reinforced concrete or granite. A diamond wheel rated for hard materials will glaze and lose cutting performance in soft abrasive materials. Always match the wheel specification to the material being cut using the application chart in the STIHL documentation.

Dry cutting with diamond wheels: Diamond cutting wheels must always be used with water on the TS420. Dry use with a diamond wheel overheats the segments, causes glazing, leads to stress cracks in the parent wheel, and creates a serious breakage risk at operating speed. If the water supply fails during cutting, stop immediately.

Failing to use water when cutting concrete or masonry: Beyond the blade damage risk, cutting dry into concrete, stone, or masonry generates respirable crystalline silica (RCS) dust at concentrations that can cause silicosis with repeated exposure. HSE guidance and COSHH Regulations 2002 require that dust suppression measures, including wet cutting where practicable, are used when cutting silica-containing materials on UK construction sites.

Operating without PPE: The TS420 produces airborne particles, high noise levels of 98dB(A) sound pressure, and vibration at 3.9m/s² on both handles. Every operator must wear safety glasses to EN166, ear defenders to EN352, a dust mask rated FFP3 for silica dust, safety boots, protective gloves, and a hard hat where overhead hazards exist. This is a legal requirement under the Personal Protective Equipment at Work Regulations 1992.

Applying lateral pressure to the cutting wheel: The cutting wheel must be guided straight through the material without tilting. Lateral pressure causes the wheel to bind in the cut, creates a kickback risk, and accelerates segment wear on diamond wheels. If the cut begins to close and bind the wheel, stop the engine and support the workpiece to open the kerf before resuming.

Storing fuel mixture beyond 30 days: Two-stroke fuel mixture deteriorates within 30 days, causing carburettor deposits, starting difficulties, and performance loss. Mix only the quantity required for the immediate working period. If storing the machine for longer than 30 days, drain the fuel tank completely.

Safety

The TS420 is a professional petrol cut-off machine governed by the Provision and Use of Work Equipment Regulations 1998 (PUWER). Under PUWER, employers must ensure that anyone operating this machine is trained, competent, and aware of the risks. The machine generates high noise levels requiring hearing protection. Vibration levels of 3.9m/s² on both handles require exposure time management under the Control of Vibration at Work Regulations 2005. Cutting concrete, stone, and masonry generates respirable crystalline silica dust requiring control measures under COSHH Regulations 2002, including wet cutting wherever practicable. This machine must never be used to cut asbestos-containing materials under any circumstances. Never use circular saw blades, carbide-tipped attachments, or wood-cutting accessories on this machine. The machine must be operated by one person only and must never be started indoors or in enclosed spaces due to toxic exhaust emissions. Read the STIHL instruction manual in full before first use.

Maintenance

Before each use, inspect the cutting wheel for damage, check the fuel system for leaks, check the idle speed adjustment, and confirm the cutting wheel guard is secure. At the end of each working day, clean the machine, check and retension the V-belt if required, and inspect the anti-vibration elements. Weekly, clean the cooling air intake slots and check all accessible nuts and bolts for tightness. Replace the spark plug after every 100 operating hours. Replace the air filter only when a noticeable loss of engine power occurs. Change the fuel pickup body annually. All maintenance beyond that described in the STIHL instruction manual must be carried out by an authorised STIHL servicing dealer.