OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers SB45 bedknife...sharpen or replace?

This is a picture of the fixed blade wear my mower has. the "shiny" part is about 4mm wide and fairly even along the length of the fixed blade. the wear is (by my guess) at an angle of about 2 degrees. The cut is not much better than my rotary mower at the moment. The blades are not contacting and I can get aprox 1/2 to 3/4 turn of the cylinder blade when spun by hand, but it is tending to grab and rip the blades of grass rather than cut them cleanly.

My question: am I better off having this sharpened or milled flat and square, or should I replace the knife because I will probably loose a fair bit of meat on the knife to return it to square ...and it could take some costly labour time?

Sorry the picture isn't great but I think you should be able to see what I mean.

Cheers

It would be best to take it to your engineer and see what they say, I am not an expert on these yet... But I do know how to pull one apart now

Hi again, I must agree with Joe here, remove the reel and the sole plate with the bottom blade attached, and take both to your engineer....he will examine the bottom blade and instruct you as to its serviceability....he can replace it for you if it is too far gone, and also advise on the serviceability of the bearings.

Beammeup, from your picture you appear to have the bluntest reel blades I've ever seen, and I thought I'd seen some blunt ones. That, plus what may be too much clearance between reel and bedknife, would produce the outcome you are getting. Your description of what is happening, and of your bedknife, suggests what you need is a routine resharpen of both items, followed by proper adjustment of the clearance between them. Of course they must be sharpened simultaneously by the same expert. I seem to recall deviosi telling you where you can get an excellent job for $45, which is a highly attractive price. Remember you need to have the reel bearings checked by the expert, and you need to try to get him or her, or better still someone from your local bowling club, to instruct you in adjusting the clearance between reel and knife: that is the main determinant of how well it cuts, and how long it is until you need another resharpen.

Grumpy, when Joe was at my place last week, as I had to have my Scotty 45 reel and bottom blade resharpened, I got Joe to video the removal procedure. The replacement also will be videoed, as well as the adjustment procedures. I will also be replacing the bearings. After editing, we will post it for future reference and the archives.

Thanks for the replies. I think my course of action is clear now. Grumpy's assessment is noteworthy!

Any chance you could send me the unedited video of reel and knife removal Deejay (since it is a pressing matter for me now)? I have found verbal directions elsewhere and can probably manage with those, but there is nothing as instructive as actually seeing it done.

Cheers

Beammeup, because your reel blades seem to be running some distance away from your bedknife, you can at least fix your folding-without-cutting-the-grass problem by adjustment. Try a sheet of newspaper between the reel and bedknife, and turn the blades by hand (spark plug lead disconnected, of course). If, as I expect, the newspaper is not touched at all, you could practice adjusting it - on both sides individually of course - until it cuts or tears the newspaper most of the way across, but doesn't touch the fixed and moving blades against each other. (You can't expect scissor-like paper cutting from blunt blades.)

You said the reel only turns half a turn or so, despite there being clearance between fixed and moving blades. This sounds as if your reel bearings may not be in great shape.

The reason I suggest you practice a bit more before sharpening the blades is that if you make a small error in adjustment and there is light contact between them, it won't really matter because they need sharpening anyway.

You're right Grumpy; the newspaper doesn't even get damaged between the blades. I will make some adjustments gradually (say 1/2 turn of the adjusting screws on each end at a time) and see how it goes. Thanks again.

Note that you will never get a full sheet of newspaper cut the full length without the blade hitting the reel. Thicker paper maybe.

Thanks Joe. I was using strips of newspaper about 100mm wide at different positions across the width of the reel. Still didn't get a cut or even a tight binding of the blades with the paper sandwiched between them.

Hi Beammeup, unfortunately the video is on a thumb drive and on its way to Joe Carroll's for editing....file to large for email, nearly 600Mb and of course segmented until edited......

Removing the reel and soleplate is not difficult, here's how:
1. Remove the chain case cover screws.
2. Undo the nut on the chain tensioner and slide down to slacken the chains, then remove the joining links and cutter and drive chains
3. Remove the nut that holds the cutter sprocket
4. Using a gear-puller remove the sprocket and the half-moon key from its key-way (keep it safe for replacement later)
5. Remove the upper halves of the cutter bearing holders by undoing the 2 screws on each.
6. Now looking at the cutter reel from the front....lift the reel from left hand side and slide up and out of the machine.
7. Remove the soleplate with bottom blade attached.
Your done!
Take both to the engineer for sharpening.

Replacement is the reverse of the above procedure.
However, before replacement, don't forget to loosen all nuts on the adjusters and wind both up so that the new reel doesn't contact the bottom blade during replacement.
Best of luck with it and please let us know how you get on.

Yeah thanks for that Joe, you will hear a lot of hoo-haa about cutting the paper....the machine is designed to cut grass not paper....from experience adjustment is a slightly tricky business due to the nature if the adjustment fittings.
Providing the cutter adjustment screws and nuts, reel bearings are in good order, reel and bottom blade sharpened professionally...it should be a case of lowering the reel carefully until contact is made then lift it slightly so that a minimum of clearance exists.

The trouble then sometimes starts when you proceed to tighten the nuts....the adjustment will be out a fraction and you have contact with the knife-blade again.
Damn!! Back to the drawing board....No, seriously, it is then a matter of patience, undo the outside chassis nuts slightly, the cutter adjustment nuts slightly, and raise the reel a smidgen and lock it up again. Eventually, you will get it spot on. If you're really lucky, sometimes you get it right first time.

Hi Deejay. Yes, I have already discovered that tightening things after thinking the setup is right leads to minor movements that bring the bed knife and cylinder blade into contact...trial and error seems to be the way to go.

Hi again Beammeup, yes mate you're right there, but that is the nature of the beast....just as an aside, the cutter adjustment screws with nut are available or if needed the cutter clamp, bolt and screw adjustment assembly complete are also available. If you wish I could PM you the details.

Video should be up tonight all going well, and I will post it tomorrow morning.... I would do it now but I have to wait for my off peak internet at 11pm to upload any faster than 5kb/s

Thanks for the heads up Joe, will look forward to seeing it!!

Hi Beammeup, the video is in place now; Click HERE for the info...We hope it is of help for you.

Thanks so much for this Deejay. Great job!
Love the tee-shirt!

No probs mate, we hope it helps you...
BTW...the 'T' shirts are available from the 'Online Store' (contained in Site Links in the left hand navigation panel) under apparel.... look great and great quality

Hi Deejay et al,
Well I have just removed the cylinder and sole plate with blade according to your excellent video instructions. I had to borrow a gear puller from a neighbouring mechanic; this was the trickiest part because the puller was far too big for my needs and tightening it without having it fall off was very tricky. I finally resorted to using a long cable tie as a second pair of hands around the puller legs...a piece of cake after that! The bad news was that one of the bearings was as dry as sun bleached bones and immovable from the shaft; How the bearing itself turns at all amazes me! It is precariously standing in a penetrating oil bath with a couple of props on the cylinder to stand it vertically at the moment. The other bearing doesn't feel too bad but I will replace both. About how much should the new bearings cost and can you recommend a source for them?

By the way, there was no felt disk for retaining oil on either end of the cutter shaft.