tree stump

A Stump Grinder Buyer’s Guide

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As with any large, purchase, there are some key considerations to take into account when choosing a stump grinder for your home, farm or business.

As expected, your needs dictate the choice of stump grinder that you need. Likewise, this must be considered alongside the power output and efficiency of the model.

Additionally, durability and quality construction are important considerations as this machine has rotating parts that are subjected to wear and tear during use, and it is expected that you should service it after using it for some period.

High-quality construction reduces the frequency of service and maintenance while minimizing the odds of SG breakdown during use.

Nonetheless, the key considerations to make when choosing the right SG for your needs can be narrowed down to the following:

Type of Stump Grinder

Reluskie / Public domain

The type of SG that you need is determined by your existing and anticipated workloads, worksite location, and budget.

As mentioned earlier, there are 5 types of SGs, and the tow-behind and self-propelled types can feature heavy-duty construction to allow for handling of heavy workload.

Usually, for residential tasks, a handlebar SG is suitable because of its high performance-to-cost ratio as compared to heavy-duty models.

This means that even though you can use a self-propelled SG to remove a tree stump in your yard, using the handlebar SG is prudent because it can perform the same job at a much lower cost.

Also, if the worksite includes tight spaces, then you need to look for a compact SG.

In summary, the handlebar SG can handle residential tasks, while the self-propelled and towed SGs are for heavy-duty work.

Cutter Wheel

Stump-grinder

The maximum momentum that the rotating cutting disc can attain during use determines its ability to meet the needs of existing workload.

As it has been mentioned previously, the 4 factors that determine the workload are the stump age, hardness, size, and number of stumps.

This cutter momentum is a product of its rotational speed and its (cutting disc) weight. As expected, the weight of the disc is a function of its size, shape, design, and material.

Relatedly, momentum creates the high pressure on the tips of the cutting teeth that allow the teeth to slice through wood.

Because pressure increases if the tip of the cutting teeth has a smaller area, that is, if the teeth is sharp, then it follows that sharp teeth, high rotational speeds, and heavy disc weight are the prerequisites for chipping hardwood stumps with ease. The rotational speed is measures as revolutions-per-minute (rpm).

You are expected to determine your existing workloads based on the 4 workload determinants explained above, as well as anticipate your future workloads.

This allows you to know what type of SG you need, in addition to figuring out what type of cutter wheel you will need.

Size of the cutting disc

Also, you need to consider the size of the cutting disc because it determines the cutting depth.

Most importantly, your workload would determine if you need to use a toothed steel cutting disc, cutting disc with carbide teeth, or cutting wheel whose teeth have been bolted to the rotor plate (to form the wheel).

They type of cutter wheel chosen also influences machine maintenance because the most critical maintenance involves changing the cutter disc due to broken or worn-out teeth, or removing the cutter to sharpen its teeth.

The direction of rotation (clockwise or counter-clockwise) of the cutter wheel is also important as it determines the (front or back) direction of where the woodchips are thrown.

It is recommended that should choose a model whose cutter wheel throws chips away from the operator as this reduces the risk of injury when grinding away a tree stump.

A deflector plate can help direct the chips away from the operator, and it is a good safety addition to your stump grinder.

Cutting Depth

tree stump

The resistance of the wood to being grinded by the bladed cutter wheel constitutes the load against which the momentum of the wheel must overcome in order to cut the stump.

As expected, the deeper the wheel goes, the more the load (as the core dendrochronological rings are harder than peripheral rings); and if the load exceeds the wheel momentum, then the wheel can become stuck in the stump, and this can disrupt power transmission between the engine and the bladed wheel.

Moreover, the wheel is axialed on a shaft, and this means that the wheel cannot go deeper than its radius because the wheel shaft will hit the stump.

To prevent the operator from damaging the SG by pushing the cutter wheel too deep into the stump, manufacturers recommend a maximum depth that the wheel can be pushed into the stump without causing any damage to the equipment, or causing a noticeable depreciation in stump chipping.

This maximum depth is called the cutting depth, and it is usually measured in inches. Expectedly, the size and material of the cutter wheel, as well as the engine power output determine the cutting depth.

As expected, your desired cutting depth is determined by the stump size.

Usually, the cutting depth is equal to the height of the cutter tooth – which is, the distance from the rotor edge to the tip of the cutter tooth.

In models whose cutter head feature a safety shroud, the cutting wheel can be lowered till the lower edge of the shroud covering is just above the stump.

Engine power

Husqvarna_SG13_stump_grinder
Charles & Hudson / CC BY-SA

The four-stroke IC engine burns gasoline or diesel to produce power – during the power stroke – that drives the crankshaft, which then transmits engine motion to the cutter wheel through a motion (or power) transfer system connected via the clutch.

As expected, the spinning speed of the cutter wheel is determined by power output of the engine, while the momentum of the wheel is a function of both engine power output and wheel mass.

Therefore, large wheels with many teeth require an engine with a high-power output. Engine power is measured in terms of horsepowers (HP) or watts (W). For interconversion, a HP is equivalent to 745.7W.

Usually 8HP is needed to grind bulky stumps. Even so, it is recommended that you acquire a model whose engine power output is at least 12HP, as this can cover your future needs should there arise a need to grind bulky, freshly-cut hardwood stumps efficiently and quickly.

Ease of Use

Another consideration is how easy is it for you to handle and use the SG machine. Well-designed models with good handles and easy-to-access controls are considered ideal.

Even so, it is recommended that you should try to use the SG machine before you purchase it so that you find out whether you are comfortable using it, or not.

Additionally, an expert can be availed to help you learn how to use the SG properly, or even help you to choose the best SG based on your knowledge and skills levels.

Normally, it is recommended that you choose a model with an ergonomic handle that features handle cushioning.

Also, an emergency button in automated control units are a useful safety feature as they allow you to stop the grinding wheel in case of an emergency or accident.

Weight

The weight of the SG affects handling, with heavy and bulky models being more difficult to handle as compared to lightweight and compact models. Usually, it is recommended that the machine should weigh 300pounds or less.

Also, the weight determines if the machine can be carried on truck beds, or they need to be towed behind the vehicle.

Warranty and Aftersales Services

High-quality SG models are normally backed by warranty. Also, genuine SG models usually have a warranty. Therefore, you should check for warranty as it assures you that you are acquiring a genuine and quality stump grinder.

Another advantage of warranty of the SG parts is that it allows you to easily and cheaply receive spare parts should some of the machine parts be damaged or wear out.

Additionally, if the manufacturer offers after-sales services, including repair and part(s) replacements, then it is an added advantage that you should consider.

Cost

Lastly, you should consider the model cost as you cannot acquire an SG that is beyond your budget.

Nonetheless, the most important consideration should be the cost-to-performance ratio as this ensures that you acquire the best SG in your budget range.

The aforementioned 8 considerations, SG construction design, build quality, and durability can be used to grade and scale SG models in the market today so that the top stump grinders can be identified.