Blades vs Carbide Teeth

Tooling is the single largest running cost decision on a forestry mulcher, and it is usually made in a hurry at the end of an order. The choice is not about which tool is better. Blades cut wood; carbide teeth survive rock. The question that decides it is what fraction of your rotor’s working life will be spent touching something other than clean timber. If the answer is close to none, blades will cut faster, finer and cheaper. If the answer is anything meaningful, and on most Australian road, rail and mine-site clearing it is, carbide durability outweighs blade efficiency before the first tank of fuel is gone.

How each one works

A blade, sometimes called a knife, is a hardened steel cutting edge bolted to the rotor and presented to the material at an angle. It works like a plane iron: it slices fibre cleanly, shears it off and throws it back into the housing to be reduced further against the counter-combs. The energy per cut is relatively low because the edge is sharp, so more of the available hydraulic power goes into removing material rather than into pounding it.

A carbide tooth is a tungsten carbide tip brazed or fixed into a steel body that sits in a welded or bolted holder on the rotor. The tip is blunt by comparison and works by impact and abrasion rather than by slicing. Carbide is far harder than hardened steel, so it tolerates stone strikes, grit and buried wire in a way an edge never will, and it is far more brittle, so a direct hit on a large rock chips or shatters the tip rather than rolling it over. Both tooling types are offered across the Shearex VM excavator range and the HM front-mount range, so on those heads this is a specification choice rather than a choice of machine.

Where the difference shows up on site

Rock and ground contact decide most of this

Walk the site before you specify tooling. Road cuttings, float rock, gravel fill, buried fencing wire, old bitumen and stony ridge country all end up in the rotor’s path, and none of them care how sharp your blades are. A single decent strike can roll or break several blade edges and stop the head until they are changed. Carbide tips chip and wear rather than failing outright, so a head with a few worn tips keeps producing at a reduced rate. In mining and pipeline corridors and stony road-reserve country, that tolerance is the whole argument.

The corollary matters too. On genuinely clean sites such as plantation residue on sandy soil or farm shelterbelt work where the rotor can stay out of the dirt, blades are not exposed to what kills them and their efficiency advantage is real.

Cut quality and particle size

Blades produce a cleaner cut and finer, more consistent particles, because a slicing action leaves a shorter, tidier fibre than an impact does. Carbide tends to leave a coarser, more shredded product with more stringy material. Whether that matters depends entirely on what the client specified. For bushfire fuel reduction, a finer particle sits closer to the ground, breaks down faster and reduces the fuel load more convincingly, and some fuel-management specifications describe a finish standard in exactly those terms. For a solar site being levelled and covered, or a firebreak that only has to be trafficable, particle size is nearly irrelevant. Agree the finish standard in writing before you price the job, because the number of passes needed to reach a fine finish is the biggest hidden variable in mulching productivity.

Passes, power demand and fuel

Because a blade removes material with less energy per cut, a blade-equipped head often reaches a given finish in fewer passes or at a higher travel speed in clean vegetation. Carbide generally needs more power for the same reduction and holds the rotor closer to its power limit, which shows up as fuel per hectare and as heat in the hydraulic system. In an Australian summer that is not trivial: a head running hard on carbide can push oil temperature to the point where the carrier derates. See the hydraulic cooling and heat guide. A bite-limiting rotor helps either tooling type by controlling how much material reaches each tool, smoothing the power spikes that slow the rotor and stress holders; the Shearex VM range lists that design with G2.0 balancing as standard.

Sharpening versus replacement

The two tooling types have different maintenance rhythms and different demands on the crew. Blades are sharpened or turned and eventually replaced, which means the business needs a sharpening routine, a spare set to rotate and someone who will actually do it. Sharpening is cheap in parts and expensive in discipline, and blades run blunt cost fuel and passes long before anyone notices. Carbide is not sharpened. A worn or chipped tip is replaced, and the cost sits in the part and the labour to change it rather than in a workshop process.

Holders are the part buyers forget. Whichever tooling you run, the holder it sits in also wears, and on a rotor that has taken repeated impacts holders can crack before the tools do. Replacing them on a welded rotor is a much bigger job. Price holders, liners and skid shoes alongside the tools, as set out in the wear parts guide.

Operator technique and hardwood change the economics

The fastest way to destroy either tooling type is to push the head into the ground chasing a clean finish, which brings more wear, more fuel, more dust and more rock exposure. Blades punish that harder than carbide does, but neither survives it indefinitely. If the client wants a scalped finish, that is a different job with a different tooling budget. Dense eucalypt is hard on tooling in a different way again: the fibre is tough and the bark on many species carries embedded grit, so blades blunt faster in hardwood even without ground contact. See the Australian hardwood guide.

The numbers that matter

No responsible figure can be published for tool life per hectare, because it depends on species, soil, rock, finish standard and operator technique far more than on the tooling itself. What follows is the structure of the decision rather than a promise about wear rates.

Factor	Blades	Carbide teeth
Cutting action	Slicing with a sharp hardened edge	Impact and abrasion with a tungsten carbide tip
Tolerance of rock and soil	Low; edges roll, chip or break	High; tips chip and wear rather than failing outright
Cut quality	Cleaner cut, finer and more consistent particle	Coarser, more shredded, more stringy material
Power demand per unit removed	Lower; often fewer passes in clean vegetation	Higher; holds the rotor nearer its power limit
Failure mode	Sudden loss of several edges on one strike	Gradual loss of production as tips wear
Maintenance	Sharpen or turn, then replace; needs a workshop routine	Replace the tool; no sharpening
Consumable cost structure	Lower unit cost, higher replacement frequency in dirty ground	Higher unit cost, longer life where contamination is present
Secondary wear	Holders, liners, skid shoes	Holders, liners, skid shoes
Best fit	Clean sites, fine finish specifications, softer material	Rocky, contaminated or unknown ground; ground-contact work

Both tooling types are available across the Shearex VM and HM ranges, and the heads also carry Hardox 500 bolt-on liners and skid shoes plus the CONVEX DX protection system, which are what stand between the rotor housing and the material the tooling throws at it.

Running both: split tooling by contract

Contractors with a mixed book sometimes keep two sets of tooling for the same rotor and change them by contract rather than by wear, which only pays where changeover labour is modest against job length. The more common arrangement in fleets with more than one head is to dedicate tooling by machine: the excavator head that works batters, drains and unknown ground carries carbide permanently, and the front-mount machine doing clean broad-acre passes carries blades. That matches the exposure profile set out in excavator mulcher vs skid steer mulcher.

Cost logic

Illustrative only, with round hypothetical numbers. Assume a 60 hectare regrowth contract on clean sandy soil. Assume a blade-equipped head averages 0.5 hectares an hour and a carbide-equipped head 0.4 hectares an hour to the same finish, so 120 hours against 150. At an assumed all-in machine and operator rate of $240 an hour, that is $28,800 against $36,000, a $7,200 advantage to blades before tooling is counted. If blades cost an assumed $2,500 in replacement and sharpening across the job and carbide an assumed $3,500, blades win the contract by roughly $6,200.

Now change one thing: assume the site has scattered surface rock and the blade-equipped head suffers three strikes that each cost two hours of downtime and a set of edges. At the same $240 an hour that is $1,440 of lost time plus an assumed $2,000 in extra edges, and on a remote site a stoppage may also cost a crew and a float movement. The production advantage disappears quickly once contamination is real, which is why the site walk matters more than the specification sheet. Record tool cost per hectare, litres per hectare and hectares per productive hour on your own jobs using the cost per unit calculator.

Decide with these facts in hand

• A physical site walk covering cuttings, gravel, previous land use and likely buried debris
• The client's finish standard agreed in writing, including particle size and ground disturbance
• Species mix and bark character, since grit in bark blunts edges without any ground contact
• Unit price of tools, and separately of holders, liners and skid shoes
• Whether the rotor uses welded or bolted holders and what replacement involves
• Australian stock position and lead time for the tooling and holders quoted
• Whether your workshop will genuinely sharpen and rotate blade sets on schedule
• Changeover labour hours if you intend to swap tooling between contracts
• Measured tool cost per hectare, litres per hectare and hectares per productive hour from a trial

Frequently asked questions