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Collection, Preservation and Display of Old Lawn Mowers

A beginners problem with a replacement bottom blade.


This problem may seem obvious to most of you here but I am absolutely stumped.  I have nobody to ask for advice and everything I know has been gleaned from experimentation so it was inevitable that I would get stuck at some point.

At the moment I am renovating a mower for my grandad.  He doesn't get on very well with his rotary mower as he finds that it tends to run away with him and if he turns the speed down it doesn't cut very well.  So I have bought him a second hand Qualcast Suffolk Punch 35s (1991 model I think) and I am trying to get it up and running.  I know this isn't exactly old and it definitely isn't a classic but this is my first project and I have more worthy models lined up.  I have dismantled the cutting mechanism, replaced the cylinder with a refurbished one, cleaned and degreased everything and hosed it all down with a modern spray lubricant before reassembling it again.  I have also bought a new bottom blade on ebay as the old one has a large dent in one end and I am told that they are such hard work to straighten that you may as well replace them.  It was advertised as being for a qualcast 35s but the problem is it doesn't seem to fit.

It is the same shape and width as the old one but it seems to be too thick.  When I installed it I attempted to adjust the cylinder height using a method I found online (you doubtless know it, it involves a piece of paper).  The problem is that the cylinder scrapes along the bottom blade along the whole of it's length, in other words it is too tight.  I have loostened the adjustment bolts until they are rattling loose in their sockets and held the cylinder up by hand as I have turned it but it makes no difference, it still scrapes badly.  The only way that I can stop it scraping is to loosten the bolts holding the bottom blade, but this is less than ideal as it could allow the bottom blade to move during use and affect the cut.  I don't really want my grandad to have to check the blade before every use.  The old blade seems to have a step in it, for about 9/10ths of it's length it tapers down to a thin edge, but the new blade does not.  A blade on another model I have looked at is the same shape as the new one but it looks as though it has been bent to make it fit better, which is definitely not a good solution.

I am stuck as to a solution.  I would rather not have to buy another blade as I have very little money at the moment.  Also how would I know that the new one would fit properly? I don't know whether to try and block out the bottom blade with something (but what? a washer wouldn't fit), to try and find a tool shop that could grind it down for me (no idea where to start with that one) or whether to just give up and put the old one back on and hope it doesn't cause too much of a problem.  Any suggestions or advise would be gratefully received.



wristpin Thu, 03/04/2014

Have to say that I've never encountered this problem  - usually the other way round where a many times ground cylinder will no longer reach the bottom blade!!

An image would help but I'm assuming that you have bought something like this but a 35cm item.…

If it's a genuine original part it should fit ok but I suppose that there is a possibility that it could be a badly produced pattern item.

Your "refurbished" cylinder - is it the right one for the machine? Is its diameter the same as the one that you have removed?

Couple of things to check - you do have the "return" springs installed under the cylinder bearing holders so that when you release the adjusting screws the holders rise under spring pressure and hit their stops?

The "hump" of the blade sits in side chassis plates and is secured with the shaped "wedges" with the retaining bolts running through them, the blade and the chassis side plates and finally the "captive" nuts? Slackening the bolts may allow you to tip the blade a fraction away from the cylinder and you may be able to retain this when re-tightening the bolts.

Without being there, hands on, I'm guessing that it is either an assembly problem or a badly made pattern part but an image or two would help.

Where abouts in the country are you? There may be a member near you who will offer assistance.

IntempestaNocte Sat, 05/04/2014

Wasn't expecting such a quick reply so I haven't checked the forum for a couple of days.  Thanks for getting back to me.  I bought the parts a few months ago and it has taken me quite a long time to get round to attempting the repair owing to the weather so I no longer have the auction listings.  The cylinder I bought from these guys:…

​The bottom blade I bought from a guy called alanmsmower and he seems pretty reliable looking at his feedback.  I am pretty sure it was not an original part though, it looks quite new and has been painted black rather than the traditional green.

The diameter and length of the cylinders are the same as far as I can tell, might be an idea to measure them.  But in this case it is definitely an original part from a 35s so it should be alright.

I have the springs in place, yes.  It doesn't so much rise as sit there, the springs aren't very... springy.  Haven't tried pushing down on it to see if they work properly, I will have to try that out tomorrow.  A very amateurish oversight on my part really.

I have tried loostening the bolts to try and tip the blade but I was not sure whether tightening would push the blade back into it's original position.  If you think that might work I could give it a try.  I need to take the blade off again anyway as one of the wedges had a "wing" snapped off (god knows how) and I need to replace it.

I currently live in Newcastle-Under-Lyme.  If you let me know what pictures you would like to see I will try to take some when I have another look at it.  Thanks again for the help.

wristpin Sun, 06/04/2014

Interesting but puzzling !

Movement  of bottom blade. There won't be very much  and yes, it may move back as you tighten things up but you never know.

Springs. Interests me that you describe them as not very springy. - they are fairly strong. From memory, to fit the bearing housings the adjusting screws need to be fully undone and the housings tilted against the spring and then pushed into place against the spring pressure. Once "over centre " they stay in place

I am just wondering if your springs have been cut down to allow a well worn cylinder to reach a worn bottom blade. Seen this done sometimes in conjunction with an enlargement of the hole in the LH chassis side plate where the shaft enters the chain case and even an extra link in the chain to allow the cylinder to drop down far enough. Is the chain very slack ?

Bottom blade. How does the profile compare with the one that you have removed?  Obviously buying a genuine original (F016101509 £26.25 +vat I think ) is the safe bet but blades from Central Spares or Garfitts should be OK but no doubt there are some bad pattern ones out there.

Not sure what else to suggest !


greensleaves Tue, 08/04/2014

Hi there  older no for  bottom  blade is L101509 as wispin stated  ,the no has been  updated but contains the 6 nos as listed. Please note the older models have a different part no which could be the problem you have got without looking has the bottom blade a stamped part no on it . I do have the master parts cat ref for models described.This Part no is for 35s   P/S the bottom blade pack is listed as L221133 . hope this helps a little. If i have a guess the wrong bottom blade supplied just a guess.ROB

wristpin Tue, 08/04/2014

That L221133 part number is no longer listed and I've never come across it. I'm guessing that it was for a "pre-pack" containing the (F016)L101509 blade and two bolts and maybe two retainers. The sort that was designed to be hung on "popular parts" merchandising displays .

I'm fairly sure that there was only ever one version of the "corrugated" bottom blade and that if yours is wrong it is because it's a poorly made "pattern part"; have you been able to check its profile against the original from the machine or a genuine replacement? As far as I know, Suffolk/Qualcast never stamped a part number on their bottom blades however at least one pattern supplier did.

DJD Tue, 26/01/2021

Looking at this old post with no good ending makes me wonder if the owner slackened the drive chain to the cylinder off, something easily forgotten.