My problem is with a Webb H12R-A manual lawn mower which has the blade set on the lowest setting possible but doesnt cut the grass

Is the blade on upside down?

The problems with blades are common for newbies because it is really difficult to find a good blade. That's why I feel a need to tell you about Oregon 396-719. You can read good reviews on it and decide why you need it because this blade is really cool.

Are you sure that it is the lowest setting and not the other way around.

Hello Uriah Gayle,

Yes... 5 blade cutting cylinder... Neds to be clea, lubed, sharp & well adjusted.

You need to look closely and understand your mower works by a scissor action. You should have an opposing blade on the bottom where each of your rotary blades actually scrape against.

In proper condition the edges should be as close and as sharp as scissors (see "mr lawnmowers" at the bottom).
"TOOL FREE" adjusting.

As I recall as o child... (middle of the last century)...
the contact of the blades you could feel the resistance
and HEAR the blades scraping like the high quality, clean...
sharp & well oiled shears they are!!

Hope this helps.

I https://www.bing.com/search?q=Webb%20H12R-A&qs=n&form=QBRE&pq=webb%20h12r-a&sc=1-11&sp=-1&sk=&cvid=9A906B6CFD6048EDA9FEB6F317B7927F

https://www.bing.com/search?q=Webb%20H12R-A&qs=n&form=

http://www.mrlawnmowers.co.uk/lawn-mowers/webb/webb-h12r

Are the blades turning when you lower the deck? If not, your belt may be slipping or it's off the pulley. Once you lower the deck and lift your foot off the the brake / clutch it should engage because the slack is now taken up on the belt, so slipping, belt jumped off or belt stretched out.