What are the myths and facts about backlapping?

What’s more important, the speed at which the operators mow, or the quality of the surface that results from the cut? As well, which is more important, how quickly a reel is ground, or the quality of the resulting grind?

General Information
Backlapping has become a controversial practice in the field, and while Neary Tehnology encourages doing what is needed to maintain high cut quality standards, we do not profess that you HAVE to backlap when using our grinding system. In fact, all spin grinders have the capability to do in-season touch up without the need to backlap. It should be made clear; however, that if you do choose to lap, it will not “kill your turf” or “ruin your bearings”, and can indeed be a viable maintenance practice if conducted as intended.

FACT or MYTH: Backlapping will ruin bearings.
Manufacturers choose bearings for specific applications, and the reel is typically designed for bearing loads to withstand ten times the loading, which may occur for the lapping process. Example: A tapered roller reel bearing used for a 5” to 7” diameter reel is capable of working under a radial load that ranges from 1,200 lbs. to 1,700 lbs. The load deflection for a bedknife to pass the compound grit during the lapping process is less than 100 lbs., substantially below the load ratings of the reel bearings. It is a fact that impact spin grinding will produce a much greater radial load on bearings than lapping ever will.

FACT or MYTH: Backlapping forces water and grit into the bearings, causing premature failure.
In years past, lapping compounds were oil-based and required high pressure to be washed from the reel. There are still some compounds today that do not easily rinse off the reel. However, with good quality lapping compounds, normal hose pressure can be used to clean the reel. This eliminates the potential for high pressure to push water and grit past the seals and into the bearings.

FACT or MYTH: Lapping takes a lot of time and doesn’t do anything.
The fact is that lapping correctly is a very quick preventative maintenance practice that is very effective when performed correctly. The key is to do it in a timely manner, with reels that have been ground properly, using the proper materials, and performing the practice correctly. The objective of a backlapping schedule is to keep the edges at an optimum, while avoiding the potential for dulling to increase to a level where grinding must occur.

For this reason, backlapping modes have been put on most hydraulically driven cutting units (or as an option) and if used in a timely manner, two minutes lap time per reel should be all that is required. As the reel wears, this lap time will increase due to more surface metal needing to be removed.

To effectively produce an even finish and to minimize the lap time as described above, the operator needs to stay with each reel for the two minute time span, redistributing the compound to keep the abrasive material cutting at the maximum rate. If this type of practice is followed, the process is fast and effective.

Four factors that affect whether backlapping will prove to be an effective practice:

  1. How dull was the reel when you made the decision to lap? Remember, lapping is a preventive maintenance process. If you have let the reel go too long between lapping, then cut quality can suffer.
  2. How much relief was left on the reel blade? The efficiency of the lap process will decrease as the season progresses, and if the relief has worn away, lapping will be less effective in generating an edge. If lapping a reel where relief does not exist (or a reel that has been spun ground only), there can be excessive wear on the bedknife.
  3. How long do you backlap? You need to lap long enough to effectively put an edge on the reel and the bedknife. “Lap” time depends on how dull the reel is, how much relief remains, and what materials are being used to lap.
  4. What is your backlapping procedure? If you don’t stay with the reel for a brief period and keep the grit evenly dispersed, the quality and effectiveness of the process may not match expectations.