Finish (or grooming) mowers typically have two or three blades and are designed for quality mowing of turfgrass. They are not designed to cut tall, weedy grass. They have multiple gage wheels and rollers that allow a relatively low cutting height with minimal scalping.
Height of Cut
Height of cut with a rear-mounted finishing mower is generally controlled by gage wheels. Quality finishing mowers have four gage wheels. By setting all four wheels to the same setting, you can control the height of cut. You then merely drop the 3-point hitch all the way down and let the mower ride on the gage wheels. Some cheaper finishing mowers have only two gage wheels so the front of the deck must be carried by the tractor the same way a rotary cutter is carried, and they must be adjusted the same way as a rotary cutter. To measure the height of cut, park the mower deck on a smooth, level (preferably paved) surface, and measure the distance from the ground up to the cutting edge of the blades (be sure the tractor engine is turned off). This measurement should be the same for all blades.
It may come as a surprise that the deck should not be run level. With any rotary mower, it is desirable to set the front slightly lower so that the blade cuts at the front and the rear of the blade does not recut the grass or drag on the grass. This will reduce the power requirement and provide a cleaner cut. This slight angle should be designed into your finishing mower so that all you have to do is set the front and rear gage wheels to the same position to achieve the correct “nose down” position.
When running a finishing mower, the sway bars or chains on the 3-point hitch of the tractor should be reasonably tight to assure that the mower follows straight behind the tractor and doesn’t sway. This is especially important when you have to back up with the mower.
Freedom to Pivot Vertically
A finishing mower must be able to pivot vertically about the lower link pins of the 3-point hitch to allow the mower deck to follow ground contours, yet it must also have a limit on this flexing motion to allow the mower to be raised for transport. All finishing mowers employ some type of moving linkage on the upper hitch point to allow this, but improper adjustment can negate it. You must adjust the upper link of the 3-point hitch on your tractor to allow some flex of the mower deck but still be able to lift the mower. This adjustment is somewhat subjective, but you should adjust the length of the upper link out enough that when you lift the 3-point hitch above the normal operating point, the rear gage wheels remain on the ground for a while as the front of the mower lifts, but the rear gage wheels eventually lift at least a foot off the ground when the 3-point hitch is completely raised.
A finishing mower must also be level from side to side. The easiest way to check this is to bend down behind the deck (with the PTO disengaged) and sight over the deck at the tractor rear axle. If the deck is not parallel with the tractor axle, you will need to adjust one of the lower 3-point-hitch lift arms until it is parallel.
All of these steps are simple and take only a few minutes, but they contribute significantly to both the quality of cut and the longevity of your mower.