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Subject: Torque Guides

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Kimberly    Posted 03-15-2021 at 19:20:53 [URL] [DELETE]        [Reply] [Email]  
  • Torque Guides
  • Are there any torque guides I can use? For example, looking for the pto shaft retaining bolts I see P.T.O. Bearing Retainer Nuts 12-15 ft.lbs on https://fordtractorcollectors.com/service/specifications-and-data/?fbclid=IwAR0ixp35hjiVlN4JAKFiSvVfCfbFHLm-MtRoPNHmxlqLv7FlumPi__qfKVg.

    Sounds low to me for that application; I would think torque that low with running equipment off the pto would find the bolts vibrating loose. What is a PTO cover bolts? THey are listed at P.T.O. Cover Bolts 35-40 ft.lbs. Then I see that the P.T.O. Shifter Plate 40-55 ft.lbs; is that the side cover that has the PTO lever to engage/disengage the PTO? If so, then that sounds a bit high to go to 55.

    Then I saw this: Axle to Center Housing Nuts 55-65 ft.lbs. If that is the trumpet; then I only torqued them to 30; that was probably a disaster waiting to happen.

    I don't think I am reading things correctly or know what they are referring to.

    Jock (OR)    Posted 03-17-2021 at 21:10:59 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • To add to the confusion, torque values change depending on the friction applied to the fastener. The friction is in two places, under the head/nut where it contacts the part, and the engagement surfaces of the threads. I am not including such variables as misalignment and side loads on the fastener, which are pretty hard to calculate.

    Dry threads take more torque than oiled threads. A "slick" lubricant can make it easy to over-torque and stretch the fastener too much. I do not recall any advice on the effect of thread locker on torque values, but it must be acting as a lubricant.

    I sometimes see mention of correction for "oiled threads" in torque charts. Often, there is no mention of such variables.

    Bruce(OR)    Posted 03-18-2021 at 14:11:04 [URL] [DELETE]        [Reply] [Email]  
  • Re: Torque Guides
  • You forgot to mention the n"German Torque" factor.

    TheOldHokie    Posted 03-18-2021 at 09:58:17 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • The engineering formulas for torque to tension calculations contain a friction coefficient term called the "K-factor". The lower the K-factor the more tension produced for the same applied torque. In practice there is a wide variation in the predicted versus actual tensions produced for any given fastener and thread condition. In general the lower the K-factor the more reliable the torque to tension calculations become. Here is a table showing how various thread conditions affect K-factor and the "scatter envelope" of the resulting values. As you can see Loctitie generally reduces the K-factor resulting in more reliable tension results. Data and claims courtesy of Henkel.


    PS> Any fastener torque chart that does not specify thread conditions used in the calculations is not worth the time it takes to read it.

    Jock (OR)    Posted 03-19-2021 at 11:41:48 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • I thought that Loctite was supposed to only be applied to dry threads. That is why they recommended special degreaser and "primer."

    I take two items from the report:
    First, Loctite is very similar to oil in lubricating threads.
    Second, zinc plating gives better consistency in toque and clamp values.

    TheOldHokie    Posted 03-19-2021 at 14:18:33 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • No.mention of degreaser or primervin the TDS for 242. In fact it mentions K factor for oil lubricated phosphated fasteners. It does suggest activator if a faster cure is needed.

    Zinc plating significantly reduces torque requirement as does oil or PTFE. Conditions are important if you are set on torqueing things.


    Kimberly    Posted 03-20-2021 at 22:30:25 [URL] [DELETE]        [Reply] [Email]  
  • Re: Torque Guides
  • If tighten securely means using a 3/8 ratchet then I found I could get close to 40 foot-pounds on the pto shaft by pushing hard. I went back and used the torque wrench and tighten each to 40. I am assuming good to go. I didn't lubricate although the threads might not have been completely dry; I used a hand held wire brush to clean the threads and I used a tap to clean the bolt holes; my die that is marked 7/16-14 doesn't seem to fit the bolts and I find that strange.

    TheOldHokie    Posted 03-21-2021 at 19:27:47 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • I figure the handle grip on a 3/8 ratchet to he roughly 6" from the center of the socket. To get to 40 lb-ft of torque you need to apply 80 pounds of pull. Thats a pretty good grunt for me but doable.


    Kimberly    Posted 03-21-2021 at 20:17:10 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • Simple torque is t=Fr. Force times radius; perpendicular, so no resolving force vectors. However, here we are not doing a simple torque. We are applying it to a screw which is an incline wrapped around cylinder. The forces get more complicated.

    TheOldHokie    Posted 03-22-2021 at 04:49:30 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • No. Torque is and always will be simply T=FR. That is the value a torque wrench measures.

    The screw threads transmit that applied torque axially which results in the generation of axial tension (clamping force) along the center axis of the fastener. That is the force that stretches the fastener and makes it act like a spring. The formula for calculating (an approximation of) the tension generated from an applied torque is:

    F=(T x 12) / (k x D)


    F = axial tension (clamping force) in pounds
    T = applied torque in lb-ft
    D = diameter of fastener in inches
    k = a dimensionless coefficient of friction (K-factor)


    Tim Daley(MI)    Posted 03-16-2021 at 17:24:13 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • Kim-
    We have a torque value chart in our How-To's -click on the LINK if you don't already have one. Torque is the value set for yield strength by material and size for any fastener. Torque is a term often misunderstood and overused. Many do not know the proper method of torqueing a fastener. It's done in three steps, not all at once. Many do not know the different settings; there's inch-ounces; inch-pounds; foot-pounds; and Newton-meters so know what you are dealing with and how to convert each. Nm are usually used with metric fasteners. You might be amazed to see how close you can get with your hands first then check with a torque wrench. Your tractor, your call.

    Tim Daley(MI)

    Kimberly    Posted 03-16-2021 at 19:40:48 [URL] [DELETE]        [Reply] [Email]  
  • Re: Torque Guides
  • Thanks Tim. I do have the FO-4 manual and know that sometimes they will list the torque in the paragraph of the section.

    I just don't want to screw up; Normally one can easily reach 30 foot-pounds with a 3/8 drive ratchet.

    TheOldHokie    Posted 03-16-2021 at 05:14:52 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • There are a lot of variables in a torque calculation. It is not as simple as a one size fits all chart based on fastener size and grade. If your shop manual gives you an engineered number trust and use it. For most general applications when it comes to concerns about vibration induced loosening anaerobic thread lockers are your friend.


    Kimberly    Posted 03-16-2021 at 19:56:50 [URL] [DELETE]        [Reply] [Email]  
  • Re: Torque Guides
  • All of the parts are screwing into the centre housing so all that material is the same. The lift cover has a high torque requirement, I think listed at 57 to 65 foot-pounds. That is bolted to the centre housing, same cast iron material. So if the cast iron in that area can take that torque then so should the other areas. However, I wouldn't think you need to torque the pto shaft to 65 foot-pounds and I wouldn't. I guess 30 to 40 foot-pounds if there isn't a listing. Now the hyd. pump is cast aluminium and over torquing those might might result in warpage or cracks. I will probably take them back to the 25 foot-pounds. The problem is the manuals I have found talk about pump to transmission and it is not bolting to the transmissions, it is bolting to the centre housing.

    It is like the trumpet to center housing; by the size of the bolt and stud, it would suggest 30 foot-pound but then I read to torque them higher. I just don't want to screw up here. I am use to torquing every nut and bolt on a car to a specification.

    TheOldHokie    Posted 03-17-2021 at 06:29:36 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • As I said its more than just "material". I suggest you use the numbers from the manual. They are the very best data available engineered by very knowledgeable and experienced professionals to fit the specifics of the application. In many cases physical tests are conducted by the engineers to evaluate fastener performance under these very specific conditions. Why would you feel it necessary or appropriate to second guess them?


    Steve Dabrowski    Posted 03-18-2021 at 17:49:26 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • @ TOH: Everyone knows these torque guides are just a liberal plot to blot out our freedoms to tighten our nuts and bolts the way we all want. Everyone knows that a bolt is made to be tight and the tighter the better, so give em a grunt! Don't listen to these over educated elitists with a bunch of letters after their names!

    Zeke (OR)    Posted 03-20-2021 at 14:15:22 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • My Uncle Jack told me “stop an Inch and a half before it breaks”. True story

    Steve Dabrowski    Posted 03-20-2021 at 15:46:11 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • I don't doubt it, only problem is it has to break to calibrate the inch and a half!

    Zeke (OR)    Posted 03-21-2021 at 11:03:27 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Torque Guides
  • Sort of defeats the purpose of measuring torque. Dad says “A quarter turn before it breaks”. Can you tell that they were brothers?

    Kimberly    Posted 03-16-2021 at 19:41:57 [URL] [DELETE]        [Reply] [Email]  
  • Re: Torque Guides
  • Thanks TOH

    Douglas    Posted 03-23-2021 at 20:44:45 [URL] [DELETE]        [Reply] [Email]  
  • Re: Torque Guides
  • There is no other feeling like the one you get when deep down in your gut when you realize that you just screwed it all up with that last tug. Pop goes the housing and it will be the most costly one too

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