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  1. #11

    Join Date
    Apr 2000
    Posts
    610
    Location
    Ontario
    Tractor
    Ford 1710: Loader, Hoe, Snowblower, Box scrapper & 3ph Forks

    Default Re: shear pin vs. slip clutch

    Shear pins are on the PTO shaft. The ones perpendicular to the shaft on the spline collar. Maybe there are other arrangements as well.

    Decent bolts are made with an ID code on the head so you can tell exactly what a bolt is, if a bolt book is available. I wish I had one when I worked on early '70's British motorcycles. Sometimes you could find American SAE, several metric standards and British Whitworth bolts on the same machine.



  2. #12
    Veteran Member wen's Avatar
    Join Date
    Apr 2000
    Posts
    1,513
    Location
    Central Texas
    Tractor
    Kubota M6800SD/LA1002 Loader Kubota RTV900

    Default Re: shear pin vs. slip clutch

    SAE bolts are marked with the marks on the bolt head, ungraded are kinda use at your own risk - made from old beer cans. [img]/w3tcompact/icons/laugh.gif[/img] See post below for details. (the edit function is great)[img]/w3tcompact/icons/smile.gif[/img]


  3. #13
    Elite Member
    Join Date
    Mar 2000
    Posts
    3,239
    Location
    Eastern Virginia
    Tractor
    EarthForce EF-5 mini-TLB (2001)

    Default Re: shear pin vs. slip clutch

    Wen - Actually, the marks are:

    None, no writing - Could be Ungraded, Grade 1, 2 or 4
    3 Marks, equally spaced, no writing - Grade 5
    3 Marks, all on one side of the head, no writing - Grade 5.2
    5 Marks - Grade 7
    6 Marks - Grade 8

    There are others, but they're specialty bolts that aren't very common. (Actually, the Grade 5.2 bolts aren't real common, either.) But the important thing to remember is that 6 marks is Grade 8, not Grade 5 and should never be used as shear bolts unless they're specifically recommended, which I've never seen.

    Mark


  4. #14
    Veteran Member wen's Avatar
    Join Date
    Apr 2000
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    1,513
    Location
    Central Texas
    Tractor
    Kubota M6800SD/LA1002 Loader Kubota RTV900

    Default Re: shear pin vs. slip clutch

    Oops...The only ones I have ever used were the 1/2 hard (3 marks on head) and the hard bolts (6 marks on head) and the ungraded types. [img]/w3tcompact/icons/smile.gif[/img]


  5. #15
    Elite Member
    Join Date
    Mar 2000
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    3,239
    Location
    Eastern Virginia
    Tractor
    EarthForce EF-5 mini-TLB (2001)

    Default Re: shear pin vs. slip clutch

    Also, you'll note that I erroneously used the expression 'Grade 3' in my earlier posts. Technically, by SAE standards, there's no such thing, but unmarked bolts are often called Grade 3 in stores, for some reason.

    Mark


  6. #16
    Elite Member
    Join Date
    Mar 2000
    Posts
    3,239
    Location
    Eastern Virginia
    Tractor
    EarthForce EF-5 mini-TLB (2001)

    Default Re: shear pin vs. slip clutch

    Wen, I think I like your designations better. Let's call them half-hard, hard, and "huh?" from now on. [img]/w3tcompact/icons/laugh.gif[/img]

    Mark


  7. #17

    Join Date
    Apr 2000
    Posts
    26
    Location
    Sunol, CA
    Tractor
    Kubota L3600GST, loader, 4-in-1 bucket, backhoe, post hole digger, 5' bush hog, 6' box scraper

    Default Re: shear pin vs. slip clutch

    On my mower I have a shear pin and I typically blow through 3-4 a year in mowing the pasture. On my auger I finally bought a slip clutch. Our soil has a real rocky layer (3" - 6" rocks) about 18" down and it wasn't uncommon to lose 3 or 4 pins per hole. With the clutch I just back off and start again. So, I think it depends on your conditions. If you don't break pins much I would stick with them because they are much cheaper. If you spend all of your time changing bolts I would get a clutch.

    Dave


  8. #18
    Veteran Member wen's Avatar
    Join Date
    Apr 2000
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    1,513
    Location
    Central Texas
    Tractor
    Kubota M6800SD/LA1002 Loader Kubota RTV900

    Default Re: shear pin vs. slip clutch

    Yeah, I personally would NOT have an auger without a slip clutch. I have the same problem with chunk rock soil (as well as solid rock). I find that most people with slip clutches don't know that they must maintain them properly or they would be MUCH better off with a shear pin. [img]/w3tcompact/icons/smile.gif[/img]


  9. #19
    Epic Contributor Bird's Avatar
    Join Date
    Mar 2000
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    38,267
    Location
    Texas

    Default Re: shear pin vs. slip clutch

    JerryG, when I bought my first two Bush Hog implements, the dealer didn't have any shear pins in stock and wasn't sure which grade should be used, so I called Bush Hog and they just mailed me some spares.

    Bird

  10. #20
    Silver Member
    Join Date
    Apr 2000
    Posts
    103
    Location
    Georgia
    Tractor
    2000 JD 790

    Default Re: shear pin vs. slip clutch

    Thanks for all the information. I bought the Bush Hog SQ600 with shear bolt arrangement. Used it about an hour, works great. Could have cut longer, but I read the instruction manual first (really). Looking at the shear bolt, it is in a collar that will allow it to spin free if the bolt breaks. I don't see what keeps the PTO drive shaft attached to the bush hog once the bolt breaks. It seems that the teliscoping action of the drive shaft could allow the drive shaft to come off of the splined attachment at the bush hog end. Is this possible? Normal?


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