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  1. #1
    Join Date
    Mar 2012
    Location
    australia
    Posts
    20

    Default How to harden ride on mower blades

    These are the type of blades I use - not from this particular supplier but these types of blades.
    BLADES 38 INCH FOR JOHN DEERE RIDE ON MOWER (greenacresmowers.com.au)

    The blades get blunt quite quickly and I remove them and sharpen using an angle grinder. I'm wondering if I can heat treat the cutting edge somehow to harden them. (I have a propane torch I use for brazing so is this hot enough to use?)

    Any suggestions on how to harden the cutting edge on this type of blade?

  2. #2
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,439

    Default

    Hello Harry,

    I would suspect that the mower blades are just toughened rather than hardened ! There would be a risk of fracture if they were. Also you might find that an angle grinder is a little bit aggressive, I use a file to sharpen my mower blades.
    Best Regards:
    Baron J.

  3. #3
    Join Date
    Dec 2005
    Location
    South Australia
    Posts
    1,656

    Default

    As said above if hardened they will brake up and pieces will fly all over the place like shrapnel you could hard face them although that would cost more than new blades, I used to to just run them over a bench grinder in batches
    they were usually good for two or three grinds then into the scrap bin, they are cheap enough to be considered a consumable item.

  4. #4
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Age
    57
    Posts
    2,651

    Default

    I'm pretty confident they are heat treated (hardened and tempered) from the factory - but "steels-aint-steels", particularly when it comes to cutting blades (of any type).
    Likely they have done the best they could with the grade of steel used. Without knowing what steel it is then you'd have to experiment with heat treatment to try and improve it (unlikely) and just wouldn't be worth the effort IMO.
    We've got about an acre to mow, and a set of blades lasts me literally years - I usually give them a light sharpen annually. Because I've generally run cheap crappy old mowers, the blades typically outlast the mower itself

    If you're mowing commercially then it might be worth going to a higher quality blade that has better steel and will hold its edge longer.
    But if you're mowing crap with stones etc in it then you'll probably just kill good blades as fast anyway in which case likely more economical to just keep sharpening cheaper ones and replace them more often.

    Steve

  5. #5
    Join Date
    Oct 2008
    Location
    N.W.Tasmania
    Posts
    1,407

    Default

    I am in furious agreement with the other posters here. I would advise against any attempt to heat treat or use hard facing material on mower blades. Unless you knew exactly what you had to do, and had the correct equipment to do it, you are likely to have heat affected zones and could easily have a blade fracture with disastrous results. I once had a blade fracture on a Rover walk behind self propelled mower. One of four blades attached to the blade disc and it fractured near the bolt hole, I did not hear it hit the blade shroud, just felt the mower vibrating like mad and trying to jump out of my hands. Several years later while walking my dog along the roadside in the country I found the missing blade section probably fifty metres from where it parted company sitting in the gutter. I have heard that blades can climb from ground level when they come apart, due to the aerodynamics, and this is what must have happened in my case. I was just grateful that the missile didn’t hit anyone, and that blade may have had a sharpen (and some straightening), but definitely no hot work done on it. These days I never straighten them anymore, just in case that could lead to a failure of the blade.

  6. #6
    Join Date
    Jul 2003
    Location
    Sydney
    Posts
    493

    Default

    I wonder if Harry and his blunt mower blades are still around?
    Just in case ... agreed. Do not attempt hardening blades without forge, quenching bath, tempering oven and the know how needed to use that.
    Much cheaper to keep on buying blades.

    I used to sharpen my ride-on mower blade regularly but figured out it was a waste of time.
    What I did, was to sharpen them 'upside down' the first time I fit them ... that is, with the bevel going up rather than going down.
    I figured that blades lose their edge due to the occasional hit on stones and dirt, rather than from cutting clean grass, so I ground the blade in a way that the sharp edge is on the top of the blade and not at the bottom edge. The difference is just the thickness of the blade, however in my case the edge lasted much longer.

    Later I found out that the blade manufacturers, some of them, had copied my discovery without permission.
    That is plain rude!
    Civilized man is the only animal clever enough to manufacture its own food,
    and the only animal stupid enough to eat it.
    Barry Groves

  7. #7
    Join Date
    Sep 2008
    Location
    Riddells Creek, Vic.
    Posts
    831

    Default

    I used to use these HSS hardfacing electrodes to reclaim the cutting edge on my 48" cut 3 blade mower but I soon realized that it was not worth the effort and now I just regrind them until they are beyond repair and just replace the set. I never had one shatter, crack or turn into shrapnel.

    Hytec Electrodes.jpg

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