Retaining large nuts
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  1. #1
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    Default Retaining large nuts

    I have a 3-point mount grader blade that I occasionally use and the nut that retains the blade section of the unit had come loose some time ago. The mount is a 2"x4 1/2 tpi bolt and the nut worked down allowing the top plate on the blade to bang out the upper inch or so of thread. I suspect that the occasional swinging of the blade from one side to the other just walked the nut down. Rather than take the time to cut the whole top apart and replace the bolt mount I simply made a 1" thick washer from some 4140HT, putting the replacement nut into good thread.

    The old nut had a retainer made by drilling a hole in the middle of one flat and welding in a 3/8 nut to keep a bolt, tightening the bolt against the thread. From getting the old nut off all this really did was to make removal harder.

    Rather than replicating the failed system I was thinking of maybe trying some Loctite? Think there's a chance that Loctite would help retain that honking but nut that's a little wobbly on the threads? I'm a little tempted to dab a little weld between the nut and bolt if the Loctite isn't expected to hold.

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    There are Nylocs available in that thread configuration, and that style, along with some loctite may do the trick. There are also threaded split locking collars made just for that purpose, but I haven't seen one in that thread..but you could make one!

    If the attachment you're dealing with isn't expected to be removed often, a dab of weld wouldn't be horrible. You could also hand drill a hole for a cotter pin and use a castle nut..or double nut it..all kinds of options.

    Stuart

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    Is there room for a jam nut on top of the present nut? Loctite may never harden if the gap is too wide but if it's a new nut on good thread, it should be ok.

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    I think the original idea of using a screw/bolt to lock the nut makes sense with one modification. You need something softer between the bolt tip and the threads the nut runs on to prevent the bolt from damaging the threads. Usually something like a slice of nylon rod is used although some old timers used a piece of lead shot. Other possibility is to add a thin jam nut outside the main nut if there is room.

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    The right Loctite could be fine, but confirm with their tech reps to make sure you use the proper grade. And make sure you've got adequate leverage for the initial tightening, you may need a serious cheater tube or gear reducer to bring the bolt to the correct torque.

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    I like Atomarc's split threaded locking collar idea. Is it possible to make one from the existing nut? It'd hold a lot better than the old method, soft point or not.

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    use a tapping sized drill through the locating screw hole to put a pocket in the 'bolt' then use a dog point screw to hold the nut. It won't damage the thread as much and should give a better hold.

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    If the nut, old or new, is tight, then one flank of it's thread should be in intimate contact with the bolt's thread. That pair of thread flanks should have the needed, small gap necessary for Loctite to work. I would expect this condition to exist for all nuts and bolts that are actually tightened, regardless of the class of fit of the threads.



    Quote Originally Posted by HuFlungDung View Post
    Is there room for a jam nut on top of the present nut? Loctite may never harden if the gap is too wide but if it's a new nut on good thread, it should be ok.

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    The nut tightens the bottom of 2 plates and can't be used to torque the plates together as they do need to slide against each other to change the blade angle relative to travel. So I can't torque the nut up, and a keeper nut would likely have to come in from below, using up some of the nut's threads. I think.

    Putting in a lock bolt takes too much wrench room from the nut - I have the completely bashed one that took 2 hours to get off showing that. Slugging wrench and a 4 pound hammer, arm still hurts from that. A locking setscrew, maybe? But the nut is a grade 8 and I'd have to locally anneal it to have a shot at tapping it. Probably have to use a brass setscrew so the threads don't end up buggered, the existing one didn't seem to be tightened against the threads and the point wasn't damaged on removal.

    Loctite suggest a "high viscosity" retainer in their literature, so I'll start looking for that. The main concern is that the fit of a 2 x 4 1/2 tpi nut against it's bolt isn't exactly a 2G fit so there's likely a lot of room in the threads and so far as I know that's the limiting factor in Loctite. Maybe an epoxy?

    I should have put in a picture but it's a couple hundred feet away. I took the shot needed, here it is. The mechanism to the left is the locking tab keeping the blade from rotating on it's own - an added benifit is that it blocks the way for most 3" wrenches (all of mine, but I only have the one slugging wrench). All of this is bashed up in the typical way of construction workers not really caring about their boss' equipment, so even tightened up the 2 plates aren't going to be touching together all the way around.

    grader_nut.jpg

    Anyway, it's a lot better than it was and I can take up a little more slack, just didn't want to until I had a better way to retain the nut. Thanks for the suggestions.

    On edit: Loctite max thread goes to 1". 2" is right out there. Might try one of the red sticks anyway.

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    Now that I see what the nut does, I agree with whoever suggested making a split clamping nut. Seems like that's the best way to deal with it, perhaps adding a hardened slide washer like those used as bearing races on needle thrust bearings. That way the nut face won't get eroded by lateral movement (if it happens there).
    Last edited by Milland; 04-16-2018 at 08:10 PM.

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    You could split the nut, on only one side or all the way, and weld lugs on for one or two transverse clamp bolts. Make the nut into a threaded clamp collar. Perhaps there is not enough radial room for the lugs. If not, you could split the nut into two jam nuts, and make a thin wrench is needed to hold one while you torque the two together..

    If you can't do that you could make the jam nuts, then drill and tap(in one of the nuts) holes for clamping capscrews parallel the the axis of the 2" bolt. Set clearance with the first jam nut, then run the second one down but leave a gap. The axial clamp screws will draw them together and the clamping will provide friction to prevent loosening.

    Another way is to make a small box-wrench for the big nut out of 1/2" plate...in the "handle" end, drill a hole for a 1/2" holddown screw, which goes into a tapped hole next to the nut. Loctite or torque the heck out of the holddown, the wrench prevents the nut from turning....unless the surface under the nut NEEDS to turn relative to the shaft and nut.

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    Or...

    Given the nut is "in a hole or corner" weld as large of nut to one face as will fit and also allow it to be removed.

    Now when tight screw in a long good grade bolt with jamb nut to secure it in place.

    This bolt simply keeps the nut from turning as it bumps against the wall.

    No damage to threads of main bolt as it is not touching.

    If that not possible then drill and tap nut to allow a bolt to thread into nut side to do same.

    Sent from my SAMSUNG-SGH-I337Z using Tapatalk

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    Nobody has suggested safety wire. Modify the nut like aircraft practice, either drill or find a place to anchor the wire.

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    Quote Originally Posted by EPAIII View Post
    If the nut, old or new, is tight, then one flank of it's thread should be in intimate contact with the bolt's thread. That pair of thread flanks should have the needed, small gap necessary for Loctite to work. I would expect this condition to exist for all nuts and bolts that are actually tightened, regardless of the class of fit of the threads.
    That would be also my reasoning but I do remember that Loctite has recommendations for maximum fastener sizes.
    For most retaining compounds M27 is the biggest recommended fastener size and 2" UNC is about twice as big as that.

    http://www.loctite.com.au/aue/conten...sers_Guide.pdf

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    Quote Originally Posted by daryl bane View Post
    Nobody has suggested safety wire. Modify the nut like aircraft practice, either drill or find a place to anchor the wire.
    Instead of drilling holes for the wire I found it sometimes easier to put a piece of sheet metal under the bolt or nut and "wrap" it around the bolt head.
    "sheet metal" in case of 2" dia bolts would be 1/8 or 1/4" thick and hammered to shape. For joints that you have to take apart more often than once in five years the safety wire or thnner sheet is easier..

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    isnt there enough room to drill a hole for a pin?

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    Quote Originally Posted by MattiJ View Post
    That would be also my reasoning but I do remember that Loctite has recommendations for maximum fastener sizes.
    For most retaining compounds M27 is the biggest recommended fastener size and 2" UNC is about twice as big as that.

    http://www.loctite.com.au/aue/conten...sers_Guide.pdf
    Amorphous Sulfur was still in use back when I wore Castles on my collar. Probably an EPA hanging offence, now, the burn-away part more than the placing.

    But the trend suggests a question to me - must provide slack for blade movement, cannot be torqued tight? Unless a Belville washer can help, why use a threaded fastener AT ALL?

    Straight cylinder, headed. Cross-pin retainer, stand-off bushing plus a few thinner washers for initial setup and later adjustment for wear.

    Should nail and hold the amount of slack needed. Fast and easy to adjust or replace, even if shorter-lived.

    Which it might not be?

    PS: 2 INCHES is not a "large nut". At all. Two FEET is.

    The nuts atop the ninety-foot studs that hold the lock wall to rock, Charleroi, PA were around three feet or larger, IIRC. Been a while.

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    I’m thinking a flat disk could be attached to the face of the threaded shaft (2 or 4 small screws) & then another small capscrew used to go back into the nut on the out side face. It’d take a while to make that though... (fair bit of hand drilling & tapping).

    Good luck,
    Matt

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    Quote Originally Posted by Matt_Maguire View Post
    I’m thinking a flat disk could be attached to the face of the threaded shaft (2 or 4 small screws) & then another small capscrew used to go back into the nut on the out side face. It’d take a while to make that though... (fair bit of hand drilling & tapping).

    Good luck,
    Matt
    Fair bit of.. work of soem kind, regardless of solutiom trialed.

    This:

    I have the completely bashed one that took 2 hours to get off showing that. Slugging wrench and a 4 pound hammer, arm still hurts from that.
    .. doesn't get easier just because "we" are six months- or thirty-six months - older.

    Shouldn't take more than 2 to 4 hours, counting go-fetch to implement the most complex of solutions so far contributed, if-even one of the simpler, faster, ones might not be the wiser route.

    That looks like a break-even, or perhaps a loss, by the wall-clock hours, even one more two-hour go.

    But Oy! The TYPE of work to wrassle it, yet-again, the hard way?

    Hate to even roll-dice on "maybe" having to face that twice if it can be avoided.

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    Quote Originally Posted by Scottl View Post
    I think the original idea of using a screw/bolt to lock the nut makes sense with one modification. You need something softer between the bolt tip and the threads the nut runs on to prevent the bolt from damaging the threads. Usually something like a slice of nylon rod is used although some old timers used a piece of lead shot. Other possibility is to add a thin jam nut outside the main nut if there is room.
    I think this would be my choice. Warner and Swasey use similar on the adjusters on their turret lathes. The longitudinal feed stops have threaded rods/bolts for adjusters. To lock the adjuster in position, a threaded hole is perpendicular to the adjuster's threaded hole. A brass disk is placed in the bottom of that perpendicular hole against the threaded adjuster, and a setscrew is tightened against the brass disk. The soft brass disk conforms to the threads of the adjuster and allows infinite readjustment and relocking without damaging the threaded adjuster rod.


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