All hands on deck

Use a locking tape measure to adjust the side-to-side and front-to-back settings on rotary mowers. The job goes quickly if you have two people and four identical locking tapes. Photo by Scott Nesbitt

Scott R. Nesbitt

Editor’s note: From time to time, GCM presents articles from its archives that are timelessly helpful for its readers. This article was originally published in November 2005.

The art of adjusting a rotary mower deck doesn’t get much attention in the golf world because the serious action in the game is on the putting green, where reel mowers are king.

The health of the turf, the appearance of the grounds and the longevity of the mowing equipment are all heavily affected by the accuracy of adjustments on rotary mowing equipment. Whether it’s a single-blade walk-behind mower, a three-blade deck on a riding mower or a wide rack of tractor-towed brush cutters, the basic concepts of adjustment are the same.

•  Thoroughly pressure-wash the machine, paying special attention to cleaning the top and bottom of the mowing deck.

•  Check that tire pressure is within the range set by the equipment maker. Especially on older equipment, make sure that each tire is the right size, tread type and pressure to its mate on the other side of the axle.

•  Lift the frame and support it on jack stands. Spin each wheel to make sure it’s not wobbly or bent. Make adjustments or replace parts as needed.

•  Lubricate the chassis. Verify that the steering system is snug, not sloppy.

•  With a strong light, check the frame for cracks, loose bolts or other problems.

•  Check all mowing deck gage wheels and rollers to assure they actually roll.

•  Clean, lubricate and inspect the links, pins, bolts, bushings, etc., that attach the mower deck to the frame. The deck linkage pivot points should be snug and move smoothly.

•  Remove the mower deck drive belts or at least relieve the tension on the belts to let the blades, pulleys and spindles rotate freely. Crawl under the deck and, while wearing gloves, grab the blade tips and try to move them up, down and sideways. If they wobble or wiggle, you likely need new spindle bearings, shafts or possibly the entire spindle and housing assembly. Spin each blade and listen for rumbling, indicating bearing failure.

•  On single-blade machines, check that each blade tip lines up exactly the same with a spot on the deck sidewall. On a three-blade deck, rotate adjoining blades so their tips come as close as possible. Check that the blade cutting edges are at the same level. If not, check for bent blades by removing and stacking them; a bent blade will stand out from the pile. If no blade is bent but the mounted blades don’t match up, you’ve got a bent deck or a bad spindle mount assembly.

•  Lower the machine and move it to the flattest floor you can find. Raise the deck to its maximum height. Rotate the blades so there is a blade tip pointing straight out to each side. Use lockable tape measures to check the height at the underside of each blade tip. Adjust the deck so the blade tips are exactly equal side-to-side.

•  Now rotate the blades so they are pointing straight forward. Measure the front and rear heights, and adjust to the manufacturer’s recommended setting. For most rotary mowers, the front tip should be 1⁄8 to 1⁄2 inch lower than the rear. When in motion, the deck is pulled forward and slightly upward, taking up the slack in the linkage, raising the deck nose and bringing the blades up to level.

Scott R. Nesbitt is a free-lance writer and former GCSAA staff member. He lives in Atlanta.