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Putting Temper Back Into Your Blades

Discussion in 'Lawn Mowing' started by Canadian GreenScape, Jun 24, 2004.

  1. Canadian GreenScape

    Canadian GreenScape LawnSite Member
    Posts: 217

    I was just sharpening the blades on my gear and mentioned to my Dad (whos a welder) about not being able to keep the blades from turning blue (and taking the temper out of them as I read on here awhile ago) He said its true that heating them up to the blueish color will take the temper out but he told me how to put it back in :p He said you have to heat them up to a dark cherry color and then immediatly dip them in oil. Im thinking you'd need a torch or somthing to heat them up that much and I doubt Ill try it... but I thought it was pretty cool :D
  2. Avery

    Avery LawnSite Bronze Member
    Posts: 1,389

    Our blades do not last long enough to go through all that trouble. We only get one sharpening out of them. By the time they are dull again the sail is worn off from all the sand here.
  3. dvmcmrhp52

    dvmcmrhp52 LawnSite Platinum Member
    from Pa.
    Posts: 4,205

    If you heat too much of the blade or heat it too hot you will make the blade brittle.Unless you are experienced or have access to a heat treat oven don't do it.Grind your blades a little slower with less pressure to avoid the blueing to begin with.
  4. Canadian GreenScape

    Canadian GreenScape LawnSite Member
    Posts: 217

    Yeah thats what Dad said too... have to take it easy with the grinder I guess.. haha
  5. Sooners

    Sooners LawnSite Member
    Posts: 190

    ...52' is correct.

    I have a degree in Metallurgy (the heat treatment of steel) and wouldn't dare consider torch heat treating a mower blade.

    Everything depends on the steel the blade is made from. If you've heated it to a cherry red, it will be soft unless you quench it in oil or salt water. The rapid quench transforms the steel into a harder and more brittle structure. The steel then needs to be tempered properly to relieve the stresses induced by the quench.

    I just grind a little farther back to remove the blue area if possible. I just wouldn't want a blade to crack and hurt something.
  6. Albemarle Lawn

    Albemarle Lawn LawnSite Bronze Member
    Posts: 1,544

    Go easy when grinding, and sharpen more often so you don't have to try to remove as much metal in one sharpening session.
  7. Woody82986

    Woody82986 LawnSite Silver Member
    from DFW, TX
    Posts: 2,128

    I was just wondering if anyone sharpens their blades by hand with a file? I swap blades on my mower at the end of every day and spend about 20 minutes with a file sharpening the ones I just took off the mower and they seem to stay sharper and provide a better cut than when I use the grinder to sharpen them.
  8. skmodmsl

    skmodmsl LawnSite Member
    Posts: 74

    I have been concerned with blade temper myself. It seems that after sharpening the blades go away quickly. I have been sharpening my blades by hand with a file. It takes a long time. But it keeps the heat down.

    Heating a blade to "cherry red" and cooling will restore temper. There are way to many variables to consider. I've given up on worrying. Keep the blades as sharp as possible. Let the customer be your guide.
  9. Craig T

    Craig T LawnSite Member
    Posts: 87

    By hand with a file? You guys must have plenty of time to mess with blades. As far as heating them up, try a belt sander. I use a 36 grit and if I want a extra nice finish I will slap a 120 on just to make them shine. I can also take 3 or 4 passes with the 36 grit and still hold the blades with my hand. Unlike the grinding wheel. If you can hand grind try one you will see what I mean.
  10. BSDeality

    BSDeality LawnSite Silver Member
    Posts: 2,850

    i sharpen my blades with a belt sander. it doesn't heat them up like the wheel grinder does, nor take off nearly as much steel.

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