Hi rossf, in my opinion, there should be no contact between the cylinder reel and the bedknife. The clearance that we are discussing here is .001 of an inch...so it is minute, but it doesn't contact.... This is the reason we discuss replacing the reel bearings after sharpening to keep everything running "true".
Here is some interesting info for you to read....
Myth: You must have contact between cylinder and bedknife.
Fact: �You do not need contact between the reel and bedknife to cut turf grass. Contact between the reel and bedknife will generate heat which will have many effects on not only the turf grass, but also on the traction unit. The heat generated between the reel and bedknife will tinge the leaf blade. Also that heat can cause the bedknife to expand which will tighten the cutting unit up even more. The tighter the reel - bedknife contact, the more strain this puts on the traction unit which can cause hydraulic hose failure and premature failure of the hydraulic system�.
Contact between cylinder and bedknife causes drag requiring greater effort to turn the reel and in turn this greater effort has an adverse effect on drivelines and engines. This drag also leads to rapid wear and loss of sharp edges, as well as a poor quality of cut. With contact you have the undesirable �scissor� action instead of the desired �scything� action. It is the scissor action which damages the turf plant and can prolong the healing process.
Myth: New bedknives are �true� and don�t require grinding.
Fact: �New bedknives are certainly not true coming from the factory. Every bedknife that gets installed on a bed bar needs to be ground properly in order to achieve a consistent quality of cut. The bedknife is the single most important factor in achieving a great quality of cut. The bedknife�s job is to position the grass before the reel blade cuts it. Depending on where the position is will depend on how clean and consistent your turfs after cut appearance will look.
Bedknives will take the shape of the existing bed bar once tightened. By grinding the bed knife properly it will give you a smooth surface that you will then align to a reel that has been ground to a true cylinder. Once this is complete you will have 2 perfectly aligned surfaces that can achieve the quality of cut that everyone is looking for. It is very important that the bed knife is ground to its proper angle (manufacturer�s recommendations) in order to maintain high quality turf grass.
Hoping this information helps clear up any ambiguity.
