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Collection, Preservation and Display of Old Lawn Mowers

Backlapping, my experience so far

So from my comments on previous forum topics, I've mentioned my interest in how backlapping  could improve a mowers capabilities,  after completing the tidy up (I don't consider it a restoration as I'm a novice in all things mechanical, electrical and metal paint covering) of my Webb whippet, I tried for the first time with my newly delivered grinding paste. Here's my opinion


Obviously left the chain off for easier access to the cylinder shaft, considered attaching my combi drill to the thread but fear of damage I secured the shaft nut back on and used the appropriate socket and drill attachment,  using the star washer to aid the nut not coming loose as the cylinder to be lapped needs to spin anti clockwise from the nut end.  Finding the right speed to have the most effective grind without flinging paste everywhere is something that I'll get the hang of but I needed a shower afterwards. Was I pleased with the results, a bit disappointed, it cut the lawn but nowhere near as well as the same width Swift which I haven't touched since acquiring it at the auction at last years agm for £2. 


I cut the lawn with the swift I use, it's set quite low and cuts the grass brilliantly, or so I thought. I took it to the garage, undid the two screws retaining chain cover, released the cylinder from the bottom blade slightly, and got out the paste. Attached the drill to nut like before and gently squeezed the trigger to get the blades spinning, once I fixed the broken chain I was ready to start again, (top tip, remove chain before backlapping) although rear roller was off the ground supported by the rear cross member, stupidly I thought I could leave chain on, but the socket caught the link that joins the chain and mangled it, breaking it off,. So with the chain off the paste was soon flying all over the place, a very satisfying noise comes out of the cylinder when the blades are being ground, turning both screws gently to get the blades perfectly sharp along every edge. Before reassembly, I released the cylinder from bottom blade, I cleaned and bathed the fixed chain in an oil Bath, washed and dried the mower from all residue and oiled all the relevant places, chain back on, cover back on, back to the lawn, after resetting blades. I just couldn't believe it, it wasn't the same mower, it was smooth, made a nice little whispy noise as it sliced the grass, it rolled over the ground easier, and seemed just a well sorted Lawnmower,  to anyone who hasn't given it ago, try it, wear overalls and eye protection but try it, it's very satisfying and worth it.

Tomorrow I will give the whippet another go, not an easy adjustment so maybe that's where the problem is, I'll try and be a little more precise in getting bottom blade and cylinder to meet, but maybe an underlying issue, I should have tested mower before lapping but I was eager to do it.

Any tips please feel free to post, any name calling regarding the broken chain is welcome too

Sorry for long post. 

Triumph66 Mon, 01/06/2020

That's a very interesting feedback Lee. I am planning to get several of my mowers backlapped too at some point. A well sorted machine is a great experience. 

I have also made a note about the chains.....


wristpin Mon, 01/06/2020

The majority of domestic drills are too fast for back lapping and those with variable speed and soft start on the trigger lack torque at low speed. The ideal tool for the job is the cranked hand brace that used to be included with socket sets .

Lee Smallwood Mon, 01/06/2020

The whippet came up better the second time around, maybe a harder metal which took longer to grind, having a closer look at the blades on the cylinder, not all had a smooth finish, there were very small blotches of untouched metal I missed previously, but another 10 minutes with the paste and some very slow turns with the Webb spanner and hey presto, another, lovely cutting mower. Can't wait to do another. 

John.Sutherland Tue, 09/06/2020

I use the same process on my side wheel Lawnmowers, instead of a drill, I use a crank handle to rotate the wheel, it is certainly a good work out.