Once you’ve established turf, its routine mowing is your single-most important grounds-care practice. Mowing dramatically affects the appearance of a landscape and the health of the turfgrass plants. And it is often the largest cost factor in maintaining any landscape.
HEIGHT OF CUT
One of the most common turf-management mistakes homeowners make is cutting turf too low and not frequently enough. They don’t necessarily scalp it to the bare ground, of course—just to the lower limit of tolerance. Their objective is to improve the turf’s appearance, but the result is often the opposite.
After maintaining turf too low and cutting infrequently for a couple of years, you’ll find more weeds, more disease, more insects and generally poorer turf quality.
Specifically, these results are caused partly from mechanical removal of too much leaf tissue and subsequent physiological effects on the plant. Mowing cuts newly emerged, highly photosynthetic leaf blades. This means older, less photosynthetically active blades must carry the burden of carbohydrate synthesis for the plant. As a result, the plant weakens and root growth slows as the plant-produced carbohydrates are shunted to produce new leaves. Turfgrass in this weakened state is not quick to recover from insect and disease injury. Weeds fill in the void.
Proper mowing height is critical to turfgrass health because it:
- Allows for proper food production
- Reduces stress
- Inhibits weed growth
- Reduces irrigation requirements.
But there is more to the story than this. By removing more leaf material and maintaining a lower canopy, you change the stand’s architecture and influence the turf canopy’s microclimate. More light reaches into the canopy, increasing turf and upper-soil temperature. Consequently, temperature of lower-cut turf is generally higher than that of higher-cut turf.
High temperatures speed up metabolism and can deplete carbohydrate reserves that turfgrasses need for growth. In addition, high temperature can interact with pesticides and cause phytotoxicity.
Be aware that turf temperature may be quite different than that indicated by a thermometer on the side of a building. You must consider actual conditions in the turf. Sunlight intensity is an important factor influencing turf temperature. On a sunny day, turf temperature may be considerably higher than on a cloudy day, even when the thermometer on the side of a building reads the same on both days.
MOWING HEIGHT VS. FUNCTION
You should select a mowing height based on turf’s function. Although each species has different mowing requirements, pay attention to turf quality and weediness at each of the following mowing heights.
1.5 inches. Most of the major cool-season turfgrasses require mowing every 6 to 11 days. The quality of these turfgrasses at 1.5 inches is typically below an acceptable level (6 on the table “Mowing requirements of cool-season turfgrasses,” above), and weed cover is often high.
You should not use cool-season turfgrasses in the transition zone when water is restricted and mowing height is 1.5 inches or less. Cool-season grasses often decline in this situation, and weed cover often dominates.
2.5 inches. Increasing mowing height from 1.5 to 2.5 inches generally reduces mowing requirements by about 5 days between mowing (DBM) with acceptable turf quality.
For example, according to a study by Dr. David Minner when he was at the University of Missouri—Columbia, chewings fescue and sheep fescue required the least mowing (12 to 14 DBM) with modest weed infestation. KY-31 tall fescue had 11 percent weed cover, but its rapid growth resulted in an 8-day mowing interval. With turf-type tall fescue such as Rebel, Minner was able to extend mowing from 8 to 11 DBM. But, he discovered, there was a trade-off between less mowing and more weeds with KY-31 and Rebel.
4 inches. At a 4-inch mowing height, most cool-season turfgrasses require mowing every 10 to 24 days.
You should base mowing frequency on the growth rate of the grass, not on a set time schedule. Though this is easier said than done, it is the best practice.
Mowing frequency typically varies based on the turf’s use and location. For example, a golf course typically mows its golf greens on a daily basis, while you only may need to mow a roadside several times a year. For most moderately to intensively cultured turf areas, the best advice is to remove no more than one-third of the turf height at any one mowing. If you remove more than one-third, you may create an imbalance between aerial shoots and roots, thus retarding growth. Plus, too-frequent mowing can cause less rooting, reduced rhizome growth, increased shoot density, decreased shoot growth, decreased carbohydrate reserves and increased plant succulence.
Mowing according to the turf’s growth rate may mean you’ll mow more frequently during part of the season and follow a reduced schedule during other months. Weather conditions, irrigation and fertilization also affect turf’s growth rate.
When preparing to mow, adjust the mower to the proper height for the primary species of turf. If grass has grown more than normal since your last cut, don’t mow it to its normal height. Instead, increase the height of cut and gradually return it to the normal cutting height over a period of several weeks. If you cut excessively tall grass down to its normal mowing height, you can severely damage it, especially during warm weather. Doing so removes most of the leaf area, leaving primarily stemmy turf. This is less dense and more susceptible to invasion by weeds. Therefore, mow often enough that you do not remove more than one-third of the leaf blade. Regular mowing controls weed growth and encourages the development of dense, sod-forming turfgrasses.
Ideally, you should allow turfgrasses to rest between mowings. Research has shown that when bentgrass was given 2 or 3 days to recuperate between mowings, vigor increased. This is because regrowth vigor is related to the photosynthetic potential of the clipped plants and their ability to use stored carbohydrates, both of which increase when some recuperation time is allowed.
The commercial turf industry creates more than 3.5 million tons of clippings a year, according to 1990 U.S. Environmental Protection Agency (EPA) statistics. Grass clippings can account for 20 to 50 percent of the residential solid waste added to municipal landfills each week during the growing season. As a result, while some turf managers still choose to bag clippings, many are finding it hard to dispose of them. Many states, in fact, have banned or are planning to ban yard waste (grass, leaves and tree and brush trimmings) from their landfills.
Many industry experts say that bagging will become obsolete not only as a result of environmental concerns but because of the financial burden clipping disposal presents. A spokesman for the National Solid Wastes Management Association says mulching is increasingly becoming one of the most feasible options for grass-clipping disposal: “The most inexpensive method of clipping disposal is to leave them on the lawn. Pay more, and you can haul the clippings to a separate composting facility. You can also pay to dump them in a landfill—if you can find one that will take yard waste.”
If you are considering collecting and disposing of clippings through composting, keep in mind that this method is not cost-free. Bagging clippings places greater wear on machinery. In addition, collecting clippings and delivering them to the compost site takes increased time, labor and fuel and is an overall inconvenience, especially for smaller crews. Educating and convincing customers about composting may take time as well. Finally, if you do not properly aerate or water your compost pile, it will not mature properly and can develop odor, which can make it hard to find a location on which to place a composting site.
Even more costly is the use of a centralized composting facility. Fees at these sites are rising because the number of landfills is shrinking.
Finally, some operators use side- or rear-discharge mowers without the bags and leave clippings on the lawn. However, many in this market will not tolerate such excess clippings. For example, you must regularly collect clippings if you care for golf-course greens—not only for aesthetic reasons but also because their removal prevents interference with the ball. Plus, some commercial customers demand bagging clippings because they also prefer a more aesthetically pleasing appearance.
Obviously, you can’t avoid collecting clippings if you mow golf greens and other similar turf areas. In these cases, though, collecting is really not that significant of a problem. The clippings are minuscule in length, and most golf-course superintendents simply spread the clippings onto rough areas. However, if you have customers who would really prefer that you collect the clippings, try to convince them to discontinue bagging by describing the many benefits of leaving the clippings on the turf.
Leaving the clippings can add as much as 1 pound of nitrogen per 1,000 square feet seasonally. That can mean a 25 to 35 percent reduction in total fertilizer applied annually. Other studies have shown that, when you bag clippings, you remove about 100 to 150 pounds of nitrogen per acre every year.
You’ll gain not only agronomic benefits from returning grass clippings to the turf, but you can reap other savings, too. For example, a waste-reduction study in Florida showed that commercial participants who recycled clippings saved as much as 50 percent in mowing time and, as a result, used 50 percent less fuel. They also reduced labor costs and tipping fees to landfills and placed less wear on their equipment, especially on the bag side of the mower, which carried the extra weight.
THE BENEFITS OF MULCHING MOWERS
Although you can use a side- or rear-discharge mower to throw clippings back onto the turf, a mulching mower is really your best choice. These units are specially designed to cut clippings into smaller and smaller pieces so they will easily fall back to the soil, rather than sitting on top of the newly mown turf.
Unlike past units, today’s mulching mowers offer a much better-looking and more consistent quality of cut in a variety of conditions. Like any evolving tool, the degree of improvement has hinged on critical design elements. How air is managed under the deck dictates when, where and how the clippings will exit. Therefore, air-flow management is a pivotal feature in today’s mulching units and a key factor in determining a unit’s effectiveness.
In general, the units that have provided the biggest improvements incorporate a deck, cutting chamber and blade design that manage clippings better than older units. Skeptics remain, but these more sophisticated units do create adequate suction to “stand” the grass, cut it, hold it long enough to chop it into tiny pieces and then evenly blow it into the turf without clumping. The subtle design of the individual cutting chambers and the blades inside the deck housing play a critical role in this process.
EQUIPMENT Choosing the right mower for specific grounds-care conditions can be confusing because you have literally dozens of models, types and sizes from which to choose. As you compare mower options, keep the following criteria in mind:
- Type of grass
- Height of cut
- Mowing frequency
- Area use
- Total area to be mowed
- Obstacles present
- Safety of operator and bystanders
- Skill required for operation and maintenance
- Skill level of operators and maintenance personnel
- Equipment versatility.
Evaluate equipment choices on the basis of performance and cost, not on the purchase price alone. Cost considerations include the price paid for the equipment plus the cost of fuel, oil and lubricants, operating labor, parts, labor to make repairs, insurance and interest—less any trade-in value—for the expected life of the machine. You then should apportion the cost to the total area cut by the machine during its useful life and compared to similar costs per acre of alternative mowers.
Buy quality. Although it may be tempting to buy lower-priced homeowner models for large areas, professional users may cover several times as much ground annually as the average user, resulting in accelerated wear and increased maintenance.
FEATURES TO CONSIDER
- A good range of operating and transport speeds. You want your mower to match the terrain and density of vegetation. A variable-speed drive—mechanical or hydrostatic—or an on-the-go, high-low shift can permit slowing to cut close to obstacles without reducing blade speed, which can cause poor cutting.
- Easily adjusted cutting height and other settings. These aspects are important because you’re more likely to perform necessary adjustments if they’re easy to make. Plus, an easier job is usually a quicker job, thus saving time. Blades should be easy to sharpen or replace and should hold a sharp cutting edge. A good range of height adjustment allows the operator to match varying lawn conditions and terrain.
- Transport considerations. Consider also the number of crew members needed to load and unload your equipment, as well as the ability of larger mowers to reduce to safe, legal transport width for movement on roads or streets and through narrow spaces. If the mower is front-mounted, does it block the operator’s view when raised to full height? Will it lift high enough to cross curbs and work around similar obstructions?
- Flexibility. The mower should be able to follow ground contours without scalping and to cut close to obstacles to reduce later trimming. Mower ends and shielding should be smooth and preferably rounded to reduce damage in case of contact with trees, shrubs or other objects.
- Adequately shielded drives and blades. The mower should meet all current safety requirements. Liability for possible injuries could be blamed on the purchaser if equipment that fails to meet safety requirements is knowingly bought and placed in service. This also applies to use of rollover protective structures (ROPS) for tractors and larger mowing units. Law requires such protective devices and shields on some vehicles and equipment.
- Adequate power. You want to prevent lowered productivity from downshifting or frequent stopping when cutting heavy growth or traveling up an incline. However, too much power may overload equipment and cause rapid wear or premature machine failure.
ENGINES, OPTIONS AND MAINTENANCE
A choice between 2- and 4-cycle engines is usually available, particularly on smaller mowers. On 2-cycle engines, you don’t have to check oil because the lubricating oil is mixed with the gasoline. In fact, with these units, engine oiling is assured even when you operate the equipment on steep slopes. However, you must mix oil with gasoline in the proper proportions, a step that can lead to fuel contamination if you mix carelessly.
With 4-cycle engines, you have no oil-fuel mixing. However, you must periodically change or add engine oil.
Whether you choose a 2- or 4-cycle engine is up to you. One type is not necessarily better than the other. When operated as recommended, either should provide satisfactory service.
Similarly, a choice of gasoline or diesel engines may be available. Diesel engines generally produce more work per gallon of fuel consumed, usually last longer, will lug down better and require no regular tune-ups. However, diesel engines are usually heavier than gasoline engines of equal power, which can be a problem on soft turf. The initial cost of a diesel engine is nearly always higher, and diesels are more troubled by contaminated fuel.
Compare also the maintenance requirements of different mowers. Some mowers need more greasing and other regular attention, but certain options may reduce maintenance. Some walk-behind mowers, for example, offer an air-intake extension hose that draws and filters air from the handle area so that the engine doesn’t pull in the heavy dust and dirt from around the engine. This feature helps reduce engine wear and should extend filter-cleaning intervals. A larger fuel tank option can extend operating periods and reduce time wasted in refilling the tank.
Increasing the number of blades and sections of a mower, regardless of type, usually improves uniformity of cut, particularly if the mower can flex over uneven terrain. Similarly, many reel mowers are available with different numbers of blades on each reel to match cutting ability to turf conditions. Some reels also are reversible to permit easy clearing of foreign objects or slugs of plant materials and for easy back-lapping. However, the addition of each extra blade, joint or other component increases mower complexity, cost and maintenance. Choose the simplest mower capable of providing satisfactory cutting of the area involved.
Flail mowers, with many knives mounted on a horizontal shaft, avoid the windrowing problems of many rotary mowers. They also can handle wet grass better than most rotaries because the discharge area runs the full width of the machine. Because of the lighter blades that are generally free-swinging, the slower blade speed and the housing shape and normal trajectory of cut material, you usually have less danger of solid objects being thrown from a flail mower than from most rotary units. Therefore, some people suggest that flail machines are better suited for areas with heavy trash or where there may be large numbers of bystanders. You also can reverse some flail mowers (with blades swung forward at the bottom and up in front) for closer cutting of fine lawns. The greater number of cutting blades on flail mowers requires more maintenance and may increase the cost per foot of cutting width compared with most rotary mowers.
Front-mounting provides easy visibility of the cutting units, but the extra weight may increase steering effort, reduce maneuverability and possibly reduce visibility when raised for transport. Power units designed for front-mower attachment rarely have these problems.
Mid-mounting provides excellent maneuverability and good visibility. On tractors, it usually makes mower attachment and removal more difficult, but it is of less concern with single-purpose mower power units.
Rear-mounted mowers are usually easiest to attach and remove if you use the regular tractor 3-point hitch. Plus, your costs are reduced because of the absence of special mounting brackets or transport wheels, as well as direct connection to the tractor PTO. However, rear-mounting means low mower visibility.
Trailing mowers are usually the simplest to attach or remove. However, trailing mowers have the lowest operator visibility, and maneuverability can be a problem in tight areas. They also have the added cost of a hitch and transport wheels.
THE NEWEST MOWER OPTION
The newest entry into the mower market is the battery-powered mower. These mowers are gaining in popularity due to their low noise levels. The only commercial units available are for mowing golf-course greens. However, several consumer riding models are available, as well as an increasing variety of consumer walk-behind units.
These units have their limitations, of course. Powered by lead-acid batteries, the commercial greensmowers have a limited operating time before power runs out. You then need to recharge them overnight. They run for about 3 hours depending on temperature, terrain, battery age and other factors. Other considerations with these units include battery life, battery use (and abuse) and weight. (The batteries themselves are relatively heavy, which adds to the weight of the vehicles and thus reduces their driving range. Oversized tires have helped to compensate for this aspect.)
As for the consumer units, they run on batteries ranging from 12 volt to 36 volt. These units can cut from a quarter acre to 2 acres before needing recharging. Recharging usually takes overnight (about 12 hours).
Despite their limitations, battery-powered units have many advantages. Their maintenance is minimal, for one. The main advantage that most grounds managers see with these units, however, is their low noise levels. Golf courses situated in residential areas have been particularly interested in the mowers. (Admittedly, some gas-powered units are reaching new noise-level lows, too.) And even the consumer battery-powered units have found homes on sites where grounds managers must mow near vacationers or near hospital windows.
If you don’t sharpen your mower blades regularly, then you’re probably shredding turf rather than cutting it. When this happens, you end up with discolored grass that needs more time to recover. In addition, you put excess strain on your mowers’ engines, because they need greater horsepower to rotate or turn the blades.
A rotary mower’s cutting edge varies in length. Usually it is several inches long. Even so, only the first inch does most of the cutting, so it’s important that you keep this area neatly sharpened. A razor-sharp edge is not necessary, however. In fact, an extremely thin blade wears rapidly. Also, stones or other debris can too easily damage an extremely thin blade. Therefore, most experts recommend leaving a slightly thickened edge on rotary blades.
If you mow often in dry sandy conditions, you may need to check your blades more often. These conditions can cause blades to wear prematurely.
Step 1: Check the blade. Before you check your blade, shut off the mower’s engine and remove the ignition key. Detach the spark plug wire so that you can’t accidentally start the engine while you are working on the blade. Remove the blade from the deck (see Figure 1, above right). Check to make sure it is whole with no bends, cracks or other damage. You cannot safely straighten a bent blade. You must replace it. Likewise, replace the blade if it appears that the area where the sail and the flat part of the blade meet is cracked (for identification of a blade’s parts, see Figure 3, right). The sail is the slightly upturned, non-cutting, back edge of the blade. If a slot forms in this area, a piece of the sail could break away while you mow and injure you or someone else. If the blade appears whole and in good shape, clean it well. Remove all excess mulch.
Step 2: Grind out nicks. You can remove nicks and sharpen dull blades using a variety of techniques. Use a grinder, hand file or an electric blade sharpener (see Figure 2, page 54). (Be careful not to overheat the blade. You can recognize overheating by the blueing spots that appear on the blade. This ruins the blade’s temper and durability.) Position the upper side of the cutting edge against the grinding edge and move it back and forth. Grind only the top surface of the blade. If you grind the blade’s bottom, you will create a chisel shape. This will push the grass down. The blade tip also should be straight, with the cutting edge lower than the sail (also known as the heel). A twisted blade with the sail lower increases the engine’s power requirement and does not allow the blade to cut evenly.
Step 3: Grind the angle. Follow the manufacturers’ guidelines for the proper angle and grinding pattern, or simply maintain the original bevel. Firmly move the blade into the grinding area while moving the blade back and forth along the length of the cutting edge. Continue this motion until you have sharpened the blade sufficiently.
Step 4: Sharpen the other end of the blade next. Remove the same amount of material from each cutting edge to try to keep the blade balanced.
Step 5: File the edges. After you’ve got a good edge on the blade, file the back side to remove any rough edges that are left over from the sharpening process (see Figure 3, page 54).
Step 6: Balance the blade. A blade must be balanced before you can return it to the mower. To check, place the blade on a balancer (see Figure 4, above), or clamp a screwdriver horizontally in a vice and rest the center of the blade on that. A balanced blade will rotate so that the heavy side falls. The rate of fall shows how much out of balance the blade is.
Step 7: Grind the blade end to balance. If you need to remove weight from one side of the blade to balance it, grind off the outer end of the blade tip rather than the cutting edge. You typically can balance the blade with no more than three balance checks and two correction grindings.
Step 8: Re-install the blade. Re-install the blade onto the deck. Make sure that you position it properly and that the cap screws or nuts are properly torqued. An improperly installed blade can cause severe vibration and might work loose or break during operation.
SHARPENING A REEL
Reel mowers were common long before rotary mowers became popular in the 1950s. Reel mowers’ acceptance continues to last despite the machines’ many drawbacks. For example, they generally cost more than rotary mowers; they are more difficult to use; they have limited capabilities; and they are more complex to maintain. Reel mowers endure, however, because they produce a superior cut—especially at low mowing heights.
Reel mowers perform their job by the reel shearing individual grass blades as they contact the bedknife. The action is similar to a pair of scissors cutting paper. This technique differs greatly from the swinging-machete action of a rotary blade.
While a rotary mower with a severely dull or bent blade will continue to cut grass, this is not true of a reel mower. If the reel does not properly meet the bedknife, the machine will not cut. You make reel-to-bedknife adjustments by one of two methods. Some machines have a stationary bedknife, and you simply move the reel by turning an eccentric bearing plate on each end of the reel. Others have a stationary reel, and you move only the bedknife by turning adjustment screws at each end of the bedknife. When you no longer can adjust the cutting surfaces so that they meet, you must replace either the reel, the bedknife or occasionally both. This situation typically develops after many sharpenings have removed much material from the mating surfaces.
How do you know when to sharpen—or back lap—your mower’s reels? Look for the following conditions:
- Mowed grass looks uneven. This is a result of severely rounded reel blade and bedknife edges.
- Mowing leaves streaks of uncut grass. This condition results when one or more reel blades are bent, leaving too much clearance between the reel and bedknife. It also can result from reel blades or bedknives that are severely or unevenly worn.
- Mowed areas are higher at one end of the cut than the other. This condition results from a cone-shaped reel.
Step 1: Find out whether you need a back-lapping machine. Refer to your mower’s instruction manual to determine whether you need a back-lapping machine or whether you can perform this task without one. If a machine is necessary, first attach the cutting unit to the back-lapping machine. Elevate the cutting unit at the rear so the lapping compound flows onto the lip of the bedknife through the back-lapping process.
If you don’t need a back-lapping machine, simply follow the steps below and turn the blade backward by hand.
Step 2: Apply a water-soluble lapping solution. A water-soluble solution is easiest to remove. Apply it with a 2-inch brush.
Step 3: Turn on the back-lapping machine. Allow the reel to turn in the reverse direction for about 3 to 4 minutes. If the blades still aren’t sharp, continued back lapping will not solve the problem because most likely the bedknives are worn or flat, or the reel-to-bedknife adjustment needs actual sharpening.
Step 4: Clean off the lapping compound. After back-lapping, whichever method you use, thoroughly clean the compound from the cutting surfaces to prevent premature wear and dulling.
Step 5: Grind the bedknife if needed. Several different brands and types of machines are available to perform the sharpening process. Two basic designs exist. Either a carriage assembly moves the bedknife or reel back and forth past a stationary motor and grinding wheel, or the motor and grinder shuttle past the stationary mower parts. The basic principle remains the same for both.
Follow your grinder manufacturer’s instructions for mounting the bedknife or reel in the grinder. Improperly placed or secured parts can lead to cone-shaped reels or chipped or broken grinding wheels.
Next refer to your mower manufacturer’s instructions to find at what angle to grind your reels. Some mowers require you to grind the reels on the blade’s edge, while others are designed with a relief angle on the backside of the blade.
Remove the bedknife and attach it to the bedknife grinder.
Step 6: Adjust the grinder. Before you turn on the grinder, move the carriage back and forth and adjust the wheel to lightly contact the highest point on the edge to be ground. (Heavy contact can result in heat buildup that causes an uneven bedknife surface.)
Step 7: Move the carriage back and forth in slow, smooth passes. Don’t expect the grinding wheel to contact the full length of the bedknife at first. Look for bright sparks that travel 1 to 2 feet. Dull sparks that travel only a short distance may mean you need to dress the wheel.
Step 8: Don’t stop the carriage while the grinder is contacting the cutting edge but make adjustments throughout the process as needed. Continue grinding until the cutting edge is sharp, checking the edge by sight and feel.
Step 9: Replace the bedknife on the mower. Now you can prepare to grind the individual reel blades.
Step 10: Check for any movement—either radial, axial or end play—in the reel bearings. Next repair or replace any broken blades. Then tighten loose fasteners to the recommended tightness. Finally, clean dirt, dust and debris from each reel blade.
Step 11: Attach the reel to the grinder. For spin grinding, first make sure the alignment is correct by using an alignment tool or gauge, or you may accidentally grind the reel into a cone shape.
Step 12: Measure the reel. After you have finished grinding across the entire length of the reel, measure both ends of the reel to ensure it is a true cylinder. If your mower requires relief grinding, procedures are slightly different. Use some type of marker (such as chalk) to mark the flat edge of each blade and to number each blade. Position the grinding wheel and follow your mower’s instruction manual as to the relief angle recommended.
Step 13: Back lap again. Once you’ve finished grinding your reel blades, some authorities recommend back lapping them. Doing so establishes a contact area on the blades, which in turn ensures the proper match between the bedknife and the cutting edges.
Though performing such maintenance tasks may be time consuming, remember that preventive maintenance is the least expensive type. If you expect your machines to take care of your needs, you must take care of their needs.
SPIN GRINDING VS. RELIEF GRINDING
Some reel sharpeners offer features and methods to accomplish a complete regrind that includes single blade relief and spin functions. Others don’t, so the debate between spin grinding only and spin plus relief has emerged as a hot topic — as is the comparison of “scything” vs. “scissor” actions. Spin grinding alone produces a sharp cutting edge and is often compared to a scythe, which produces a good quality of cut as long as it remains sharp. Keeping the reel sharp can require the time-consuming task of regrinding during the busy periods of summer. If the reel blades are not maintained to a sharp edge, then the bed knife must be kept sharp by facing or filing the front edge of the bedknife. With no relief, the reel blade thickness could cause increased drag as debris is brought between the reel and bed knife. A gap of one to two thousandths of an inch is recommended between the reel and bed knife when you spin grind alone.
On the other side of the debate, if you add a relief grind or grind the back side of the reel blade off as to produce a very thin land area, you can adjust the reel to the bed knife with virtually zero clearance between the two. With new varieties of ultradwarf turf and heights of cut well below 0.100 of an inch, you can measure the amount of leaf tissue being removed only in microns.
A scissor action is attained when the reel in conjunction with the bed knife creates a shearing type action. Just like a pair of scissors, the two blades must be maintained extremely close to each other, so close that measuring would be impractical. The natural juices in the grass blades act as a lubricant and actually keep the reel blade and bed knife at near zero contact. If you want to have increased performance, you can do so by making the reel blades thinner by relief grinding, that is, by grinding away the backside of the blades.
Mowing is serious business. In 2002, about 230,000 people were treated in hospital emergency rooms following injuries related to various lawn and garden tools, according to the Consumer Product Safety Commission (CPSC).
Each year, about 75 people are killed and about 20,000 are injured on or near riding lawnmowers and garden tractors. One out of every five deaths involves a child. CPSC estimates that most of the deaths to children occurred when a child was in the path of a moving mower.
“No parent wants their child to be one of these statistics,” said CPSC Chairman Ann Brown. “Young children move quickly and are attracted to mowing activity, but they don’t understand the dangers it poses. Parents should keep young children away from any outdoor power equipment.”
The CPSC safety standard for walk-behind mowers has substantially reduced the number of mower injuries. In addition, CPSC has worked with industry on a standard for riding mowers to stop the blade if the rider gets off or falls off the seat.
To prevent you or your crew from becoming a statistic, you should be aware of safe practices for operating mowers. You’ll find advice from the Outdoor Power Equipment Institute (OPEI) and the CPSC for safe mowing practices in the boxed information that appears on pages 55 and at right. Make sure you understand this information. And train your crew to always follow these safety procedures.