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

Came across this place while looking for parts on a SB45, as I decided to fix up the one I have.

had the mower 20 odd years, and it was old before that, been trying to find out the year it was made. seems that is difficult. its a 17 greeen with orange reel (was), black catcher, 3hp BS orange also. doesn't have the original handle bars when I got it.

It pretty much done now, got a brand new briggs 3.5 engine OHV, had to enlarge the clutch to fit the bigger engine shaft, and make a new key to fit. was going to get one of those cheap Honda 5 hp copy motors only $110, but got the new Briggs instead for $275 delivered.

Front roller was a bit loose so rather than get new plastic ends i made a bigger shaft for it.

Bought a new accel cable before the motor turned up, but new motor doesn't really need it as it has an accelerator lever on it. So I thought bugger, take it back who needs one now, one less part not really needed. Motor has a manual choke and fuel cut lever as well. starts first pull, so it should.

Chain was a bit loose to the blades, as in very loose even on full adjustment it was hanging down. so removed a link, big error, far to tight now, so bought a new chain. New drive clutch cable also fitted. Whole thing stripped and reassembled without any instructions on how to do it

cleaned it up somewhat for another 20 years service i hope. Bit dirty just tested it here after the chain finally turned up past the expected delivery day. Was hoping to complete it last week to mow last weekend, but had to use the push mower because the part was late. Only had about 4-5 hours on the rebuild in total after work over a week.

Oh the green hammer paint is a bit brighter than original but ok for a quick grab from bunnings, yellow blade paint is a rust proof paint rather slow drying stuff.



I know someone who has this mower. i assume it a fairly recent one with the black briggs motor (one before the current motor I just got I assume), a rover not a scott bonnar or are they the same thing? Was trying to find some model history on all the 45's for some sorta time line of when what came out.




How are the blades done when sent away, on a lathe or bed grinder? The sole plate is easy, just not sure on the blades. Saw on here you say ground to match? I assume they are both just done perfectly straight which will match, then backhoned on the mower to match, or some sort of jig made up. however a jig won't mean you get a perfect match when fitted back onto the mower. you need smooth straight edge blades that rotate to a perfect distance to the sole plate all along it. To get that the final hone should be on the machine, well thats my thinking without any manual or instructions on the process.

LOL my latest almost new push mower hit something the other day, snapped off the plastic blade adjuster and bent the blade and bottom plate. with a spare adjuster off the last push mower, and fixing the blades I finished the last 2 metres. Who knows what i hit didn't see anything.

The numbers on the original B & S should give you the year of manufacture

Hi Steve, and welcome to Outdoorking.

You raised a lot of points in your post, and most of them are best answered by Deejay, our resident SB guru. However with regard to dating your mower, as Padman said, the numbers on the air cowl of the original B&S engine are the best estimate we can make. If you post the whole long string of numbers from the cowl we can tell you a few things about it, most of which you won't care about since you've pitched that engine anyway. The last block of numbers includes the manufacturing date.

From past explanations supplied by Deejay, I understand that matching the reel to the bedknife can be done either by lapping them together on a jig built into the special-purpose grinding machine, or on the mower itself. The reel should be spun backwards to do this because otherwise the grinding paste will round the leading edge of each blade, and the bedknife as well. The process is a bit fraught with difficulty either way, because typically the reel bearings have a little bit of slack in them, especially if they are not new, so lapping on the mower is less than ideal. Nevertheless backlapping on the mower, so long as the bearings are new and the parts are already sharp, seems to be able to extend sharpening intervals and perhaps slightly improve mowing quality.

The colours on that late SB-type mower indicate it is a Rover, not an SB. Rover bought SB and continued manufacture of the model 45 with very minor changes. Deejay can tell you what they were.

Hi Steve99, and a warm welcome to the OutdoorKing forum, and nice to welcome another Scott Bonnar owner as we all like to learn new things and tinker here.

With regard to the Scotty 45, Padman is correct, the old orange Briggs cowling numbers will give the actual date of manufacture....but of the Briggs itself...not of the Scotty chassis...No exact date of assembly exists for any particular machine, unfortunately. So the motor could be old stock, placed on a newer machine or vice-versa.

There are clues to dating a Scotty 45, here's a few things to look for...(yours is a late model)
(1) Plastic front roller ends (early had alloy), (2) Alloy height adjuster with red plastic button (early ones were brass), (3) Black plastic grass deflector knobs (early ones had screws ), (4) Twin rail engine deck (early was a solid deck), (5) Screws on the chain-case cover are vertical (early were horizontal) and on the 20" machine there was the 3 segment rear roller and later 2 segment. the paint colour varied also

The Scotty 45 was continued under Rover ownership and eventually "badge engineered" to become the Rover 45 (solid red and green coloured) but some commentators have questioned the build quality as being inferior to that of the Scotty. I tend to lean that way also.

For an explanation on spin-grinding...click HERE
Please read down further in the posts (Post Number 15182) about 'Facts and Myths'...You may find that interesting.
Once again

Thanks quite helpful I'll check out the number on the motor when I get home.

watch that video, also found a number of others on youtube from brand new machines and how to use them to home made ones.

This guy seems to have a lot of video's this one is hone the bottom blade and adjust. Not sure what he said only saw it with the sound off so far.

[video][/video]

I've moved this thread to the Questions on Scott Bonnar Cylinder Mowers forum so it can be continued - it is way out of scope for the Introductions forum. You might consider a different title for it.

Steve, I think that video is useful but it avoids some of the main issues.

He is doing the same job that Deejay does with his "Bedknife Buddy", a small file set in a plastic block. This tool sharpens the bedknife's cutting edge. That is an operation that needs to be carried out regularly, not rarely like resharpening the reel. The problem is to remove only a very small amount of metal, and keep the entire length of the bedknife edge not only perfectly straight, but also parallel to the axle of the reel. The video makes no mention of this entire subject: he just trusts his air tool to do all that for him. I rather doubt that it can, though it may come closer to doing it than the Bedknife Buddy can. Whatever the tool does not do inherently due to its design, the operator has to do through skill and care. Meanwhile I was not comfortable with his failure to deburr the top edge of the bedknife after he sharpened it.

Note that on the subject of paper cutting, the video says it is a test you routinely make whether you are using no contact or light contact. Because there is more than one opinion on this subject and Deejay is sensitive about it, I won't go into it further.

[video][/video]

Thanks for moving.Won't let me change the first title.

This machine could be useful. I could make something similar to this, would save some time, If I get some time to make it it will......

I like how it grinds the other way is small and simple. machine home page

The video is currently not available on Youtube - perhaps it will heal up after a while. Meanwile I changed the thread title to the new one you nominated, and that overwrites all of the posts.

There have been many a simple method tried, but a good engineer doing a spin-grind is the method (in my opinion) that's the best.

The direction and lower speed this machine grinds at would be better than the bumping higher speed grind to the front on the blades as in the other video. You wouldn't get the horizontal shock to the blades as much by coming across the blade at lower spinning speed. From an engineering point this machine is a better method for a blade type hone for these mowers. The straight on front approach grinding is good on solid round things (solid metal rod etc), where the stone is in constant contact with the material.

Bit expensive for home use at $5,000 for a new machine, Ok for a shop to recover that cost. I have to make something similar, or find a shop that grinds a similar way down the blade low speed.

Now I know how they do it, these options are ok so far....................

But better still is relief grinding the blades which is original manufacture specs, improving the final cut even further. Not something I can do at home cheaply, much more difficult to do.
Do any of the places you guys get your done do relief grinding on these blades? That is perfection if you can get that done.

If you can recommend who does relief grinding I'll just use them next, bugger making something if I can get this done.

Hi Steve, that video I initially posted just as an example of what spin grinding is...That particular 'Garfitts' grinder is absolutely nothing like the specialist machine my engineer uses to spin grind...and this guy just did all the reels for the 2011 Australian Lawn Bowling championships held last October here in Wagga. He is a perfectionist at his craft.
The grinding wheel on the machine my engineer uses is huge compared with that flimsy Garfitts outfit.

Now re 'blade thinning' or 'relief grinding' please read the facts and myths....Please click HERE this might be of interest for you...

yeah i guess it makes sense if you have no contact then you don't need relief. plus the edge being thinner may mark up more easily.

Hi Steve, yes mate, I think in the long run it boils down to personal preference and what works best for you...but that is the nature of the beast working with cylinder mowers. They need to be well maintained to do the job that they are designed to do and have a lot more moving parts that the rotary....they are definitely not for the faint-hearted, and do require time and effort to keep them in tip-top condition.