OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Scott Bonnar Model 65 in NZ

Well, finally got my new old mower home, it had been sitting outside for two years, with the only cover being the catcher sitting over the engine. Terrible!
From what I can see, it hasn't had a lot of use, but on disassembly seems to have a broken alloy pivoting cylinder carrier on one side.
It is held on by a big recessed nut on a left hand thread, and no socket I have seems to fit. Are SBs metric or imperial.I would have thought metric, but the bolts I removed to take the cutter unit out seemed to fit a 9/16 W open ended spanner, rather than 14mm which was a bit snug to be the proper size.
This nut looks like about 28mm, for which I do not have a socket. Previous owner seems to have used a centre punch to remove it, which has swollen the nut on one face, so I will have to try and dremmel it back to its original shape before I do any more.
Do you think the pivoting carrier could be welded?
I am also struggling to get the bottom blade off the base plate, and wondering whether a shop could sharpen it while still attached? Any thoughts?

Hi rayray,

The bolts won't be metric ,more likely Whitworth or SAE.

Yes the pivoting alloy carrier could be alloy welded.

It's best to remove the bottom blade off the base plate for sharpening.

There doesn't look like a lot of room to get a socket on that nut ,you may need a tube box spanner or
use a blunt chisel or pin punch or centre punch to try to undo the nut .

Cheers
Max.

G'day rayray,

Before I begin, have a look at [pics. 1 & 2].

I hope I can be of some help to you regarding this problem you have with your Hex. Lock-nut ¾" UNF [Unified Fine], Left Hand Thread.

To get at it, you will need to remove the damaged bearing housing completely, and the best way [and by far the easiest] is to use a bearing puller [see pic. 3]. The hole in the middle of the cylinder shaft surrounded by the red marking in your photo, is specifically there for this purpose, and also for use when your cylinder is being professionally sharpened using a lathe.

First though, remove the grease nipples then spray some WD40 into the holes. As for the alloy housing, you can use a large Stillsons wrench e.g. to try to gently rotate it, without causing any further damage.

Then, if it won't come off, you can use a bearing puller to remove it. Once it is completely off, you can then get the two parts welded together. The nut [see pics. 4 & 5] will be fully exposed and you should be able to get it off, remembering of course that it is a left handed thread nut, so you will need to turn it clockwise for removal. To prevent the cylinder from turning when you do this, place a stout piece of wood between the blades and your bench-top.

Regarding the bottom blade, once you have removed both alloy bearing houses, lock-nuts and bottom blade adjusters [see pic. 6] you should be able to take your cylinder and bed housing with the blade still on it, to a specialist and get them machined [i.e. both ground on a lathe, to get a perfect match]. Your bottom blade will need to be in pretty good nick though, for this to happen.

It is worth pointing out here that my bearings [see pic. 7] are sealed. They are [NSK 6304 V 845], and there is a Circlip [52mm INT] on each housing that holds them into place. I should also mention that these mowers, when they where first released over here, they had [NSE 6304], or the equivalent of, installed, which were sealed on one side only, and the idea was that the exposed side would sit tightly against the alloy holders wall, and you would use the grease nipples to lubricate them. Having said that, the grease nipples are still attached to my alloy housings, as they prevent any fine debris getting in, as this helps when it's maintenance time...

I hope this helps you get out of your predicament,

Cheers,

mice_elf