A Cut Above
There is no doubt that the cleanness of cut produced by a well maintained and sharp mower has a dramatic impact on the health of the sward and so the overall quality of the playing surface. Rather than achieving a cleanly cut appearance produced by a sharp unit, turf cut with a blunt mower will appear ripped and ragged as the leaves are pulled and torn between the cylinder and bottom blade.
In 2006, Bernhards and Company approached the STRI requesting they investigate the differences between two methods of maintaining mower sharpness; the non-contact method using their products and the back lapping technique:
1. the traditional method of ‘lapping’ or ‘back lapping’ requires light contact between reel and bedknife at all times to produce a clean cut. This technique causes dulling of the two edges and without frequent ‘back lapping’ will result in an inferior cut. To maintain the tolerance between reel and bedknife the cutting unit requires infrequent sharpening (grinding), but regular ‘back lapping’. The ‘back lapping’ process consists of spinning the reel in reverse whilst applying an abrasive paste to true up the wearing surfaces.
2.The second method is ‘non lapped’ or ‘non contact’. As the name suggests this method requires clearance between reel and bedknife so that there is no contact between the two. In this set up there should be a gap between reel and bedknife, typically the thickness of a sheet of paper. This technique imposes less wear on the mower blades as the wearing process is caused purely by contact with the grass and top dressing material rather than the ‘metal to metal’ contact required for the ‘back lapping’ technique. To maintain sharpness the cutting unit (reel and bedknife) should be ground every thirty days. Also the bedknife can be sharpened regularly with a portable front face (bedknife) sharpening device known as a ‘rapid facer’. This device is magnetically attached to the bedknife and is designed to restore the front face of the bedknife to the original grind angle.
Mark Ferguson of the STRI, who oversaw the research study, concluded ‘that running mowers using the ‘non contact’ method of setting up the cutting units and using grinding to maintain sharpness was an improvement on the ‘back lapping ‘ method.’ But what do our readers think? A recent survey of our readers showed that the majority continue to back-lap for the reasons of cost and convenience.
Says Mark Ferguson: “Research conducted at the STRI demonstrated that when two mowers were set to the optimum setting, one as ‘non-contact’ and the other ‘back-lapped’, over time the turf mown with the ‘non-contact’ treatment was superior to that mown with the ‘back-lapped’ treatment. These differences in visual quality, though not huge, were statistically significant. A common concern from groundsmen is that switching to this system will cost them time and money. Our study showed that although there is a significant initial outlay both in cash and time spent familiarising staff with the new system, over time running mowers with the ‘non-contact’ system is likely to save both time and money.”
A full copy of the report is available to download from www.iog.org
Reasons for using the non-contact method of setting up the cutting units and grinding:
“Research behind the method indicates stronger/healthier turfgrass”
“Less wear and less pressure on reels, bearings and engine”
“Our cylinders are partial relief ground in winter and a perfect cut is achieved by careful quality of cut adjustment which I alone set. Year in and year out a full season without lapping is possible while still retaining quality of cut. Should a cylinder become dull then I disassemble and have sharpened but seldom does this happen. Cylinders are set with no contact.”
“It increases the lifespan of the mower by reducing friction to cutting surfaces. I don’t believe in backlapping to produce to quality cut, grinding is the only way. Just look at a grass blade under a microscope after cutting and you’ll know why!”
“The mowers are sharpened professionally rather than by me”
“This method allows for longer life of the blades”
“It is more accurate”
Reasons for using the ‘backlapping’ method:
“Ease and simplicity”
“I use this method after having them ground first, just to keep them sharp”
“We’ve been happy with this procedure over the years”
“It’s the way I was taught to set up a mower and has always worked for me. I have also been taught to back-lap and as we have our own back-lapping machine I can use this to keep my reels in good shape”
“A good result is easily achievable”
“I spin grind my cylinders then relief grind them when setting up my cylinders. I set them with light contact and use this method because it is what is recommended by the manufacturers who have spent millions of dollars on research”
“Old tried and tested method”
“To ensure proper and even sharpness along the blade contact with the bedknife”
“It’s cost-effective and I can do it myself”
“Does not last too long but it gives a sharp edge to the blade for a good cut”
“Provides a quick fix during cutting season. Once a year machines are sent away for regrind and new bottom blades”
“A cost-effective and convenient way of keeping the mower sharp although depends on the type of mower”
“The manufacturers recommends this method”
“Can be carried out on site without any disruption”
“Mainly because this is always the way we have done it though we are starting to be persuaded by the non-contact method”
“Keeps a keen, paper-cutting edge”
“The blades and sole plate act like scissors to cut the grass, this method gives the best results and causes less damage to the grass plant”
How was the study conducted?
The trial was conducted on an area of fine turf dominated by bentgrasses and annual meadowgrass, typical of a UK golf green. The trial was laid out in a randomised design with twenty plots, ten plots for each mower treatment. Two identical Ransomes GS 55 Greens mowers were used. The first mower was maintained using the ‘back lapping’ technique. The second mower was maintained using the ‘non contact’ approach. In order to maintain the ‘non contact’ mower Bernhards provided an Express dual and Anglemaster grinding system along with a rapid facer for routine sharpening of the bedknife.
Both mower treatments were set up and maintained by STRI’s expert groundsmen and the trial area was subjected to the treatments for just over a year.
1. The boldness and longevity of striping and visual quality were improved in the ‘non-contact’ treatment. The ‘non-contact’ treatment was also less susceptible to disease.
2. The ‘non-contact’ treatment had a significantly faster rate of re-growth, or that the ‘back lapped’ mower, despite being set to the same cutting height, was cutting closer to the ground.
3. The turf colour of the ‘non-contact’ plots was a little greener, an indication of slightly better turf health.
The trial work suggests that maintaining mower sharpness under the ‘non-contact’ regime can produce superior turf.
Time and money is also a consideration when choosing a sharpening method. The STRI groundstaff felt that in terms of time spent maintaining the two mowers there was initially very little difference between the two treatments.
Routine ‘back lapping’ took approximately half an hour and routine front facing took five minutes. Monthly grinding of the ‘non-contact’ mower took less than an hour, with the timescales being reduced as the groundstaff became used to the system.
A system such as the Express Dual and Anglemaster would require a significant initial outlay. However, subsequent maintenance costs would be reduced as there would be no need to employ specialist grinding companies to re-grind mowers on an annual basis. In addition it was concluded that sharper mowers that produce better quality turf will potentially save money by reducing any remedial action that has to be taken to solve problems. Healthier turf is naturally more resistant to diseases; therefore time and money should be saved by reducing chemical input.