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Broken cutting edge?

Discussion in 'Truck & Equipment Repair' started by Groove, Jan 9, 2006.

  1. Groove

    Groove Junior Member
    from Boston
    Messages: 20

    I've been running an 8' Fisher MM1 for three seasons and noticed it was time to put on a cutting edge. I bought a 5/8"x9"x8' for it with the factory Fisher bolts as I was told not to use grade 8. I was told that you want the bolts to be the weak point. Well my third time out this year and I hit a man hole cover. It sounded like my windshield shattered. I jumped out of the truck after I couldn't see any broken glass. There were broken bolts and nuts everywhere. I broke all 8 bolts all at once! I then searched for my cutting edge. I found it in two pieces! I snapped the thing clear in half.

    How often do you guys break edges?

    Should I have used grade 8? I feel like if the bolts didn't start to break, the edge wouldn't break and the edge would have (should have tripped.)

  2. JTW

    JTW Senior Member
    Messages: 137

    WOW....how fast were you going?
  3. BayviewLawn

    BayviewLawn Member
    Messages: 67

    Im impressed!Snapping all 8 bolts and the edge..geez..I would think grade 8 should be used and the blade should trip long before sumthin breaks.
  4. Groove

    Groove Junior Member
    from Boston
    Messages: 20

    You'd think I was plowing a highway but I was just doing a parking lot. I was going 10-15?

    Has this happened to anyone?
  5. Mick

    Mick PlowSite.com Veteran
    from Maine
    Messages: 5,546

    I've never had that happen, but breaking all eight bolts at the same time and the cutting edge, I have to wonder if the bolts were tight to begin with. I can't hardly see the edge breaking considering the use they commonly get. It should have tripped. I've hit some pretty big rocks that were solidly anchored. It sounded like the whole truck frame was coming apart, but nothing broke. When you said all the bolts broke was really the clue that they might not have been tight enough and allowed the edge to "flop".
  6. makplow

    makplow Senior Member
    Messages: 242

    I agree with Mick. What grade bolts did you use? Even grade #5 Its hard to believe they would all snap. Are you sure your trip is working properly? :confused:
  7. Rappa

    Rappa Member
    Messages: 84

    Ok you said you have been running this plow for three years. Did you just change the cutting edge after three years? I go through 1 or two a season per blade. Three years seems like along time if the blade gets any use. You must have worn down your trip edge significantly.

    Now you then add to the problem by purchasing a humungous cutting edge. A 9 inch cutting edge is pretty big for a plow, nevermind a blade that has a worn trip edge. You don't have enough "meat" behind the cutting edge where it bolts on to sustain a hit like that without breaking the bolts and/or snapping a cutting edge -wow-... The stress is distributed solely on the cutting edge and nothing on the trip edge.

    In the future, I would buy the regular 6 inch cutting edge for parking lots and driveways. I use an 8 inch on one of my trucks, only because it is plowing the highway and wears extremely fast when you plow the interstate for long hauls each way. The other two have 6 inch edge's. Hope my explanation makes sense.
    Last edited: Jan 10, 2006
  8. justme-

    justme- 2000 Club Member
    Messages: 2,138

    Rappa you can;t assume that. Depending on the amount of plowing an individual does if they use shoes or not, the quality/grade of the cutting edge, and their style will influence significantly the edge wear rate. I have seen commercially used blades last forever, I have seen guys run through 2 edges in a season. The base angle is supposed to be worn down before an edge is put on also.

    I have worn only half a inch to 1 inch off my trip edge and cutting edge in 6 years. Previous owner had no real wear to the base angle in 2 years.

    That said- 9 inch edges are too much for a Fisher, especially in 5/8. That's alot of steel. I have to agree I suspect the bolts were not properly tightened- one bolt snapping yeah, maybe 2 bolts, but not all of them. Are you sure you were only going 10 to 15 mph?
    Since I have only seen 9 inch edges available for municipal plows I have to presume it is a hardened edge- made for highway use, which makes them brittle so yeah- a hard solid hit is not unheard of to crack one.
    The longer the edge the more severe the angle of attack on the ground- that makes a huge difference in the trip force. I would suggest raising the rear of the moldboard (go to bottom hole) for a new 8 inch edge on a normal blade.
  9. Rappa

    Rappa Member
    Messages: 84

    You are still on your original cutting edge in 6 years???? Are you serious?
  10. Plow Meister

    Plow Meister PlowSite.com Addict
    Messages: 1,174

    Rappa, I am still on my original cutting edge in 10 years and I may have only worn down about 1.5" of edge. I am just now considering replacing it but not until next plowing season.

    Granted, a lot has to do with the amount of plowing a plow does, but I do a LOT of plowing when the snow hits. I can't imagine going through even one cutting edge a season. I just don't think that's possible. Maybe in Alaska or other high accumulation areas but certainly not the northeast.
  11. Rappa

    Rappa Member
    Messages: 84

    Plowmeister and Justme, all I can say is wow! 6 years and ten years, that's crazy! Maybe myself and everyone that I know are doing something wrong. Maybe they don't make them like they used to? Who knows... I would be curious to hear from others on this subject. I have a friend that plows a highway with his 04 GMC 2500hd and a minute mount 2 that goes through an edge every 2-4 good size storms.

    Ten years? Come on now... Does this truck go out on a regular basis?
  12. Plow Meister

    Plow Meister PlowSite.com Addict
    Messages: 1,174

    Yup. It is my primary truck. I have 5 other trucks with Westerns that have never had the cutting edge replaced and I have had them going on 7 years now and I bought them all very used.

    In a typical storm my truck goes out for about 10 to 14 hours and we get about 10 storms a season. I know the northeast gets a lot more snow than we do but in order for me to have to replace my blade even once a season I would have to plow 100 storms a season according to my numbers.

    I don't want to say you are doing anything wrong. Are you buying actual cutting edges or are you just using mild steel?
  13. Rappa

    Rappa Member
    Messages: 84

    Yeah as far as I know they are the real deal. And I don't always buy from the same place. I wish I would get that much life out of one! I started another thread in the commercial forum on this topic to see how others weigh in about the subject. I am curious for sure now...
  14. PremierLand

    PremierLand PlowSite.com Addict
    from detroit
    Messages: 1,572

    Maybe what you consider worn down really isnt worn down to other members?
  15. Mark Witcher

    Mark Witcher Senior Member
    Messages: 605

    I replace mine after about 1 inch to inch & a half of wear. I have seen lots of people run them until its wearing into the moulboard. And if you are running the Pro wings the plow is kinda held up off the ground by the rubber when the cutting edges get too short and then the plow doesnt scrape as well.
  16. oarwhat

    oarwhat Senior Member
    Messages: 166

    I hear ya rappa none of our trucks would make 3 or 4 years let alone 10 wow. My truck goes through 1 to 2 edges a season. I use 1/2" x 6". I didn't catch the 9" blade the first time i read the post. I think you guys correct that blade has to much leverage and weight. My dad and brother got the bright idea to use 5/8" x 8" wing edges we had . The weight ruined springs ,plow pumps, alignments, tires. At first it seems fine but the wear and tear is brutal!!!!
  17. Plow Meister

    Plow Meister PlowSite.com Addict
    Messages: 1,174


    The rubber on the Pro Wings wears MUCH faster than the steel of the moldboard. Not to mention that the rubber is extremely pliable and bends a lot when needed. There's no way the rubber from the Pro Wings will make the steel cutting edge last any longer.
  18. justme-

    justme- 2000 Club Member
    Messages: 2,138

    Yeah, primary truck plows regularly. 30 customers on the route on average since I bought the truck.

    Couple of things to note- the less snow on the surface the faster the edge will wear. You guys plowing commercial lots that want the snow pushed at one inch have more friction then us who trigger at 3 inches or more. If you plow treated surfaces you also have more friction- no ice layer on the pavement.

    Many guys consider the edge worn at 1 inch gone- a 6 inch edge should wear 2 inchs MINIMUM, an 8 inch edge should wear 4 inches MINIMUM.

    Now, I never wore the base angle down before installing the edge- the 1/2 inch edge is flush with the base angle creating almost triple the surface area in contact with the ground versus just an edge. The pressure of the blade on the abrasive is less than 1/3rd- wear rates are less than 1/3rd versus the single edge. Scrapes as good as a brand new Fisher without an edge, but not as good as a brand new cutting edge alone. Good enough for me in most storms and VERY cost effective.
    I tried replacing the edge last season- bought the new one and was ready to unbolt the old when it occured to me the old one was very close in size to the new one- a quick measure confirmed it was only worn about 1/2 inch after 6 years.
  19. Groove

    Groove Junior Member
    from Boston
    Messages: 20

    I sub for someone as I have 9-5 job I can't miss. This means I usually only plow half the amount of time the rest of the crew is out. Otherwise I think the factory edge would have lasted me only two seasons.

    I figured that since the cost wasn't very different between the 6" and 9" and I always hated the drift coming over the top of the plow, a 9" would last longer and allow me to push more without buying a foil. I kind of figured most people would run the 9" but neer looked.
  20. Groove

    Groove Junior Member
    from Boston
    Messages: 20

    I think they were in a Fisher bag. I'll go back to the store and look later. The guy at the store told me not to use grade 8 and to use the carrage bolts they stocked for it.