OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers SB45 Reel Adjustment

Hi Guys,

I have read various threads and watched the outdoorking youtube video of the reel adjustment all of which is very informative.

However, I have just got my reel and bedknife back from being sharpened, have thrown all new bearings into it, regreased everything and am attempting to set the bedknife clearance correctly.

I don't know whether or not I'm trying to achieve something that doesn't pertain to the SB, but in my searches I read that your bedknife clearance should be set such that if you place a strip of paper between the bedknife and reel and rotate the reel, that it should cut it exactly like a pair of scissors.

I find that i can only achieve the cutting of the paper when i more or less have what I determine to be contact with both of the surfaces where you can definately feel the reel 'drag' over the bedknife. What i find is when i back it off ever so slightly that there is no drag, then it doesn't cut the paper, merely catches it, but doesn't cut it like the scissor action.

Is it too tight? should it be cutting the paper as above and is the 'audible drag (like a metal scratching/scuffing noise, not really like a ching ching ching noise' ok across the bedknife?

Cheers!

Hi oldmatty,

I think you may open up a can of worms with this thread as there's many different opinions on setting up SB45's.

This is taken exactly from the SB45 operating instructions.

The paper test works well but ultimately you're going to be cutting grass and not paper. Perhaps you can try setting the reel with no contact and then testing the mower on your lawn. If you get down and look closely and the grass is being torn or the leaf blades are being stripped on the ends, that is unsatisfactory and requires further adjustment. If the grass is being cut cleanly like a pair of scissors would achieve, then all is well, even if it won't cut paper.

I once had a reel sharpened by a local mower shop that claimed they had the proper equipment to do a grind. When I got home and put everything back together I couldn't get a good adjustment, I had contact on some blades and not on others. When I rang the mower shop to question them, it turned out they didn't do a spin grind but a single blade grind and managed to get the reel ever so slightly out of round. Never again will I get anything but a spin grind done by an experienced professional.

Michael

Michael has given you a good summary, oldmatty. In the end, if it cuts each leaf of grass at least as cleanly as a pair of scissors would, it is correctly adjusted. Obviously it will remain sharp and adjusted longer if there is no contact - but the acid test is what a blade of cut grass looks like through a magnifying glass.

I suggest that you should not run your freshly sharpened reel at all, with contact, or you'll have damaged its new edge before you even begin. Deejay is sure to log on at some point in the day and will be able to make specific recommendations, but meanwhile please don't blunt the blades before he gets the chance.

Ok great thanks for the input.
The reel indeed has been spun ground, I can tell that by the feel of it and how it looks.

When i was installing the soleplate to the chassis I noted that there is bit of play/give (I'm talking only about the amount of movement the bolts can move in their holes in the chassis) before you actually tighten the bolts, I wasn't sure if this play mattered too much as i figured that after you 'lock' the bedknife in by tightening it, that you then set the reel to marry up to the bedknife, or am I mistaken, does the soleplate have to be installed 'true/square' to something via measurement.

Now I am cutting buffalo grass, so i can only assume that as its quite a broad thick leaf, i may not infact need to be running such a 'papercut' tight clearance?

Lastly, I've noted that you need about 8-12mm chain deflection on the large chain that uses the plastic tensioner to tighten, but I'm unsure of the other 2 chains and their required tension, i forgot to take note when i stripped it all down and now i think its too tight but cant be sure, all i know is it looks and feels too tight.

Hi oldmatty, you will find that there are 2 schools of thought here....(1) that you need slight contact and can cut paper and (2) (which is my method) that you have NO contact but minimal clearance. here is a brief extract from a professional turf care magazine:

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 if fitted�.

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 drive-lines 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.
You do not need to cut paper...the cylinder reel is designed to cut grass.

The primary chain should have a minimum of 12mm play to prevent chain stretch and primary sprocket wear. All other chains should have slight play as well.

Ok great thanks for the tips!

Some tinkering to do this arvo now

Hi oldmatty, and I hope you enjoying the tinkering.
Re: cylinder reel adjustments, if you check out the very end of our video, you will see my machine cutting grass with no bottom blade contact.

Surprisingly, not a lot of people don't realise that the cutting action of a cylinder mower takes place between the front edge of each reel blade, and the very top of the front edge of the bottom blade.
Keeping this edge sharp and true, is most important for the quality of cut.