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Thread: Make a torque wrench extension

  1. #1
    2004 Wrangler X flyboy161's Avatar
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    Default Make a torque wrench extension

    Make a Torque Wrench Extension



    Background

    I have a decent "clicker" type torque wrench with a range of 15 – 150 ft-lbs. I recently had to replace the pitman on A friend's Jeep. When installing it back on, the nut needed to be torqued to 185 ft-lbs. What to do? My first inclination was to buy another torque wrench, at a cost of about $79.99 from Harbor Freight (for a decent one, ha!). But how often am I going to use it? Practically never.

    An alternative was to make a special extension which will multiply the torque. I DO NOT mean an extension like this:






    A regular straight extension like the one above does not change the effective length of your torque wrench, and will therefore not have any affect on the torque setting.

    Now look at this:





    The big difference is that the extension shown above does increase the effective length of the torque wrench. As a result, the actual torque applied to the bolt will be higher than the setting on the torque wrench.

    The extension shown in the above picture is called a crowfoot extension, which can be handy when trying to torque hard-to-reach bolts. You must, however, use a formula to account for the length of the extension:

    wrench setting = desired torque x wrench length / (wrench length + extension length)

    For example lets say that the length of the torque wrench is 15 inches, and the length of the extension is 8 inches. The desired torque is 185 ft-lbs.

    Wrench setting = 185 x 15 / (15 + 8)
    = 185 x 15 / 23
    = 120.7 ft-lbs.

    If the torque wrench is set to 120.7 ft-lbs, the actual torque applied to the bolt will be 185 ft-lbs.


    This tool I'm making allows my 150 ft lb torque wrench to place 230 measured ft lbs on a fastener.


    Making The Extension

    The extension must have a female fitting on one end, for attaching to the torque wrench. On the other end it needs a male fitting to attach sockets. Since my torque wrench takes 1/2" sockets, all the examples below are for a 1/2" extension. If your torque wrench is 3/8" or 1/4", then resize as needed.

    Parts List:
    1/2" x 3/8" socket adapter (available at Sears for $5.99)
    Serpentine belt tool ( available at Harbor Freight for $17.99 )
    Access to a Flux wire welder (available at Harbor Freight for $89.99)
    (the wire feed welder is an awesome tool capable of doing many hobby type projects. I use mine frequently for making tools, brackets, and even did some exhaust work with it. Because of this I won't include it in the total cost of this project)


    Total cost- $23.98 + tax

    I chose the serpentine belt tool looks like this





    Notice the small bar. It has a 1/2" drive male end and a 3/8" drive female end:





    We're going to use this piece along with the 1/2" female to 3/8" male socket adaptor:





    1. Prepare the extension by cleaning the paint off of the 3/8" female end. I did this with some emery cloth and a file to clean any burrs off the metal. I clamped it in the vice to do this.


    2. Next clean the chrome off of the socket adaptor. Chrome makes toxic fumes when it gets hot (as in welding).


    3. Insert the 3/8" male end in the 3/8" female end of the extension to test the fit. Both the male and female end of the extension are square with each other meaning the squares are oriented the same.


    4. Clamp the 2 pieces together. I used a large pair of vice grips to do this. This is only until the first weld is complete. Double check to make sure that the two pieces are sitting flat against each other.


    5. Clamp the ground cable from the welder on to the bar extension and suit up (gloves, visor, long sleeve shirt). Turn on the welder and do your tack weld somewhere clear of the vice grips. Hit it a welding hammer to remove any slag and clean it with a wire brush. I used wire speed 9 for my tack weld and it looked good, so I removed the vice grips and completely welded the fat side of the adaptor to the bar.


    6. Flip the whole thin over and then weld the 3/8" square side to the bar. Clean it up and then quench it with water. This allows the molecules of steel to align properly for hardness and durability. Dry it off and grind the welds smooth, but don't take off too much of the weld.


    7. Paint the entire piece with primer and then paint. I chose black. The finished piece should look like this:








    Sources of Errors

    Worried that using an extension might cause inaccurate torques? I don't blame you. Here are the various errors that can be introduced when using an extension:
    A. If you do not accurately measure the length of the torque wrench.
    B. If you do not accurately measure the length of the extension.
    C. If the extension is not perfectly lined up with the torque wrench.
    The above errors are in addition to the calibration accuracy of your torque wrench. If you are reasonably careful, each of the above errors will be negligible. But just how careful do you need to be? See the following:

    A. You measured 15" from the mark on the handle to the center of the head of the wrench:

    But actually should use the center of the handle to the head which is 14"


    So you do the math with an 8" extension and come up with 120.7 ft lbs to get 185 ft lbs of actual torque. Because you mis-measured the wrench you have actually put 189.7 ft lbs of torque on the fastener which is a 2.43% error.


    B. you measured the extension at 8" but it is actually 7.75" center to center. Here a 15" wrench set for 120.7 ft lbs should give 185 ft lbs of torque but because of the error in the extension length it actually yields 183.1 ft lbs at the fastener which is a - 1.09% error.


    C. The wrench is not aligned perfectly with the extension. In this case this would be due to the ratchet mechanism inherent to the wrench. As I place the wrench on the extension it is perfectly aligned, but as I apply force to the handle of the wrench the angle changes by as much as 10 degrees. This is what 10 degrees looks like:





    So, here 120.7 ft lbs on a 15" wrench turned 10 degrees relative to the 8" extension does not yield 185 ft lbs. instead it yields 184 ft lbs. At 20 degrees the 185 becomes 181.2 ft lbs. at 30 degrees it becomes 176.4 ft lbs.


    Obviously degree errors do not yield linear errors in ft lbs so be careful.
    10 degrees is a .53% error
    20 degrees is a 2.10% error
    30 degrees is a 4.66% error
    40 degrees is an 8.14% error


    An interesting thing happens at 90 degrees. The effective length of the extension becomes zero and it is exactly like using the torque wrench without the extension. So if you set 135 ft lbs it will yield 135 ft lbs.


    CONCLUSION

    Making a torque wrench extension is relatively easy and inexpensive, and is a viable alternative to purchasing a separate torque wrench that will get very little use. With a little care, potential errors can easily be kept to negligible levels.
    Last edited by flyboy161; 01-12-2014 at 17:18.
    "It is in my opinion that owning a jeep must be like raising a rebellious teenager: the more you try and love it and nurture it and get nice things for it, the more it says "screw you!! I'm doing drugs and drinking because I hate you!!!" And your stuck taking it to the hospital "

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  2. #2
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    i would never recommend this to anyone myself. a pitman arm? youd be better off with the goodntite spec than trusting a crowsfoot thats not designed for that. whats the calculated spring back for that wrench at the open?

  3. #3
    2004 Wrangler X flyboy161's Avatar
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    We actually used a 1 and 5/16 socket for the pitman arm nut off the sector shaft. The idea is a longer arm increases the effective leverage. This is a pretty standard tool in aircraft maintenance. The crows foot in the illustration was for illustration purposes only. Goodntight is an antiquated and dangerous procedure that may work well for you, but I'll trust my life to torque values and something a little more than shade tree "mechanic-ing" any day


    Sent from my iPad using Tapatalk HD
    "It is in my opinion that owning a jeep must be like raising a rebellious teenager: the more you try and love it and nurture it and get nice things for it, the more it says "screw you!! I'm doing drugs and drinking because I hate you!!!" And your stuck taking it to the hospital "

    Labor of Love build
    http://www.militaryjeepers.com/commu...-Labor-of-Love

    My build thread
    http://www.militaryjeepers.com/commu...61-s-Littlebee

  4. #4
    2004 Wrangler X flyboy161's Avatar
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    On the matter of torque values, I know another goodntight style mechanic. I've so far fixed three vehicles that he has worked on. Over torqued wheel nuts, starter bolts falling out, loose control arm bolts that nearly ruined the frame mounts, loose sway bar links and a disconnected track bar that caused the girls Jeep to torque steer (she's lucky to be alive)

    Being involved in aircraft maintenance for the last 24 years, I can tell you we weed out the shade tree mechanics. I still see them from time to time, but they never last.


    Sent from my iPad using Tapatalk HD
    "It is in my opinion that owning a jeep must be like raising a rebellious teenager: the more you try and love it and nurture it and get nice things for it, the more it says "screw you!! I'm doing drugs and drinking because I hate you!!!" And your stuck taking it to the hospital "

    Labor of Love build
    http://www.militaryjeepers.com/commu...-Labor-of-Love

    My build thread
    http://www.militaryjeepers.com/commu...61-s-Littlebee

  5. #5
    Senior Member HillBillE's Avatar
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    Great write up flyboy161!

    I'll be building one of those this summer, and saving the formula.



    For avaiation, you have to have everything to spec. But, when it comes to 'ground vehicles', sometimes the old 'Good-N-tight' works OK.

    Granted, there are some guys who never grasp the idea, and go overboard.

    But, I have also found just as many guys who can 'feel' the torque, and be with 5 pounds or so.

    And that works fine for wheels, bumpers, etc.

    As long as you can get all the nuts/bolts equal.

    With Aluminum wheels, I usually will use the torque wrench, as they tend to come loose when not torqued properly.

    Steel wheels, I just do by hand.


    As long as the people remain armed,
    government knows that it cannot rule over the people by force.
    Those who stand in defiance of unconstitutional laws
    do so out of duty, honor, oath and love of country.


    "Certified Jeep Junky!"


  6. #6
    2004 Wrangler X flyboy161's Avatar
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    Agreed Hillbillie, there are some things you can snug and some you can't. The girl I mentioned above drove her Jeep for five years and just adapted to how poorly it drove. Her rear track bar bolt fell out and every time she shifted gears the Jeep pulled hard to the left. Hard enough to pull you into the oncoming lane. Her lower control arm bolts were all finger tight, causing the bolts to shift around in the holes until they were nice and oval shaped. Her axles would shift fore and aft.

    Another guy in my group had his sway bar disconnects left loose by the installer and the nearly cut the disconnect pin on the drivers side in two. Same story with another member of my group plus loose shock absorber bolts up top.

    My sons Jeep, the Labor of Love, lost a starter bolt due to the calibrated elbow of the same guy. My Jeep acted as though the battery or the starter was toast. Both checked good. Care to guess what it was? Yeah, the torque on the starter bolts, or lack thereof, caused the starter to bind when it cranked. Re tighten and good. Guess who did that? Yeah...THAT guy.

    This last weekend, we repaired the damage caused by a loose track bar bolt in the front on another Jeep. Plus found the pitman arm bolt and lower shock bolts in the rear not tight. There's no way those bolts were anywhere near torque. I know I loosened them.

    I don't torque everything. But when it comes to suspension, steering, things that keep me, my family and others around me safe I check the FSM and if it calls out a torque value, well, you bet I'll be torquing it.

    There are a couple of things on the Jeep that require....and I do mean require... A torque wrench and a very high torque value. Like your flywheel, spindle nuts, control arms. Yeah okay, my bumper bolts are snug. My door nuts are snug. Heck, even the screws in my dash are just tightened a scootch. But my steering, brakes, suspension, transmission...etc...are tightened by the book. And another thing, my 5 and 3/4" lifted Jeep rides like a stock Jeep down the road. It doesn't rattle, squeak, clunk or wander!
    :rant off:

    P.S. I mean no disrespect to anyone, I've just kind of made it my mission in life to spread the word about torque wrenches and torque I suppose. Cheers

    Sent from my iPad using Tapatalk HD
    "It is in my opinion that owning a jeep must be like raising a rebellious teenager: the more you try and love it and nurture it and get nice things for it, the more it says "screw you!! I'm doing drugs and drinking because I hate you!!!" And your stuck taking it to the hospital "

    Labor of Love build
    http://www.militaryjeepers.com/commu...-Labor-of-Love

    My build thread
    http://www.militaryjeepers.com/commu...61-s-Littlebee

  7. #7
    Senior Member HillBillE's Avatar
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    Quote Originally Posted by flyboy161 View Post
    .... lost a starter bolt due to the calibrated elbow of the same guy.
    ROFL! Haven't heard that phrase in a long time!! LOL

    Quote Originally Posted by flyboy161 View Post
    P.S. I mean no disrespect to anyone, I've just kind of made it my mission in life to spread the word about torque wrenches and torque I suppose. Cheers

    Sent from my iPad using Tapatalk HD
    No offense taken here, I also torque the important stuff.

    I have 4 torque wrenches, keep 2 at home, one at my dad's in the shop, and one at the cabin, for the tractors.

    And it doesn't cost a lot, I buy the Harbor 'Fright' ones, and they are decent.

    I've compared all of mine to both a Craftsman and another top brand (don't recall which, but my buddy was an ASE Mech at a Dodge dealer)

    The cheap ones were extremely close to the high end ones, close enough to use with confidence.


    Biggest thing, is using the same torque wrench for all the bolts , ie: all the head bolts, or all the flywheel bolts.

    That way every thing is even.

    Gotta watch for stuff that calls for 'wet torque' also, ran into that a lot while pipefitting.

    Having lube on the threads changes the torque value.


    I'll definitely be building an extension, for the few times I need higher torque, it's a great alternative to buying another wrench.


    As long as the people remain armed,
    government knows that it cannot rule over the people by force.
    Those who stand in defiance of unconstitutional laws
    do so out of duty, honor, oath and love of country.


    "Certified Jeep Junky!"


  8. #8
    2004 Wrangler X flyboy161's Avatar
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    Thanks. Yeah, the old calibrated elbow, LOL. I wish I had a dollar for every time I have heard it. But seriously, the HF wrench is just as good as the top end stuff with proper care and feeding. I've used them for all sorts of things and never had a problem. I have a tech article on my forum on torque and all the different varieties of torque. There is a lot of different from break away, prevailing, etc. I could post it here if you'd like. It has a lot of of info, but explains a lot to a techie like me


    Sent from my iPad using Tapatalk HD
    "It is in my opinion that owning a jeep must be like raising a rebellious teenager: the more you try and love it and nurture it and get nice things for it, the more it says "screw you!! I'm doing drugs and drinking because I hate you!!!" And your stuck taking it to the hospital "

    Labor of Love build
    http://www.militaryjeepers.com/commu...-Labor-of-Love

    My build thread
    http://www.militaryjeepers.com/commu...61-s-Littlebee

  9. #9
    Wheelin requires wrenchin Doppler's Avatar
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    Good write up but I just went with this, plus I can have a local lab calibrate it for me.

    http://m.lowes.com/pd_337334-22328-8...ductId=3381202
    Just a redneck with a big Jeep!

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    I've used torque wrench extensions for submarine repair in a Subsafe environment. Just as long as you calculate the mechanical difference correctly, you're good to go!!

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