Back Lapping Procedure, Introduction | National Mower 68 DL, 68 SR

BACK LAPPING PROCEDURE

	DANGER	Be extremely careful not to let the
	DANGER	brush, your fingers or your clothing
		brush, your fingers or your clothing

get caught in the reels. Wear gloves to avoid cutting fingers on sharp edges. Wear approved safety glasses to protect your eyes from flying particles and abrasives.

INTRODUCTION

Back lapping is a very important step in maintaining sharp reel blades on the cutting units.

This procedure should be performed when the reel blades and the bed knife become slightly rounded and the grass is not cut cleanly with only a slight reel to bed knife adjustment. Also, after grinding the bed knife and reels, you should back lap to establish a perfect match between the bed knife and reel blades.

RECOMMENDED STEPS

1.Adjust the reel to the bed knife so that the bed knife is parallel to the reel and light contact is maintained.

2.Reels must be run in a reverse direction to be lapped. Remove the lower drive belts and attach a back lapping machine (not supplied by National Mower) to the reels. Follow the instructions furnished by the machine manufacturer.

3.Apply the lapping compound with the reels running, using a 2" or a 3" (5 - 7.5 cm) brush. Apply the compound evenly to the moving blades.

Many types of compounds are available for lapping. We recommend a good pre-mixed water soluble compound. Pre-mixed compound saves the time required to mix, eliminates the waste of abrasive, rinses off easily with water and is available in all grit ranges from coarse to extra fine.

4.Stop the reel and examine both bed knife and reel blades to see that the cutting edges are uniformly sharp. If not, gradually tighten the reel adjuster bolts (see "Reel to Bed Knife Adjustment" above) and repeat Step 3 until the proper sharpness results.

5.Rinse off the compound thoroughly with water to remove all abrasive. Check for sharpness and readjust the bed knife if necessary. Reel to bed knife contact should be adjusted to easily cut a sheet of paper (see "Reel to Bed Knife Adjustment" above).

NATIONAL 68 SR & DL TRIPLEX

BACK GRIND IN THE

DIRECTION

OF THE ARROW

25O

Note position of

blades to reel

axis

GRINDING REELS

Reels must be ground at 25° in the direction shown by the arrow in the figure. Back grind until reel blades are free from roundness, dents and nicks. Spin grind to remove all burrs. All blades must be on the same diameter.

GRINDING BED KNIVES

For maximum cutting efficiency, grind bed knife top and front edges at 5° as shown in the figure.

68OM-06/03

68 SR, 68 DL specifications

The National Mower 68 DL and 68 SR are two outstanding models in the world of lawn care, engineered for efficiency and ease of use. Both mowers offer a range of features tailored to meet the needs of both residential and commercial users, making them popular choices among landscapers and homeowners alike.

The National Mower 68 DL is designed with durability and performance in mind. It features a robust steel deck that enhances longevity while providing a clean and even cut. Equipped with a powerful engine, the 68 DL delivers high torque and swift acceleration, enabling users to tackle even the toughest grass and rough terrain effortlessly. The mower's advanced cutting system ensures that grass is cut finely and evenly, reducing the need for additional clean-up.

On the other hand, the National Mower 68 SR offers a self-propelled option, allowing users to move with ease across various landscapes. This model incorporates hydrostatic transmission technology, which provides smooth, variable speed control. This feature is particularly beneficial for those who demand precision in their mowing tasks, as it allow for adjustments on the fly, catering to changing terrain conditions.

Both models come with adjustable cutting height options, offering users the flexibility to choose their desired grass length. The easy-to-use lever enables quick and simple adjustments without needing tools, making the mowing process more efficient. Additionally, both the 68 DL and 68 SR are designed with ergonomics in mind, featuring comfortable handles and intuitive controls that minimize operator fatigue.

Safety is another critical consideration in the design of the National Mower 68 series. Both models come equipped with protective shields and safety switches to prevent accidental starts, ensuring that users can operate the machines with confidence.

For convenience, the mowers also feature large, easy-roll wheels that enhance maneuverability. The inclusion of a bagging system offers an option for collection of grass clippings, contributing to a cleaner lawn appearance post-mowing.

In summary, the National Mower 68 DL and 68 SR combine advanced engineering with user-friendly features that prioritize performance and safety. They are exceptional choices for anyone looking to maintain a pristine lawn with minimal effort, making yard work a more enjoyable task. Whether for home use or professional landscaping, these mowers stand out in their class, delivering reliable performance time after time.