How to stiffen a bolt?

[yadnom1973]

I have a long M8 bolt passing through a part. By putting a few turns on the bolt I adjust the parts position on the threaded stud and how it functions. I also am looking at some female cam levers that by turning the matting bolt would adjust the tension when the lever is applied. Both are simple but functional solutions to a problem but if the bolt is too loose then it can turn accidentally and loose the position it was set at so I’m looking for a way to stiffen the bolts on the thread in their holes.

Some people have suggested wax but I need something that will not migrate, something permanent and the stiffer the better.

Any ideas on a permanent way to stiffen a bolt on it’s thread?

 

[Nick Hulme]

A captive Nyloc nut where the bolt enters the assembly is easy to arrange.

 

[RM-MN]

If you cannot use the Nyloc nut a really cheap way to emulate one is to use a bit of monofilament fishing line. Just push it through the threaded hole before screwing the bolt in. Different line diameters will adjust how hard the bolt is to turn or you can use more than one line. It may need to be renewed occasionally.

 

[WOB]

Loctite was invented to solve this problem.

WOB

 

[yadnom1973]

Sorry about the delay. I had to step away for a moment.



WOB - I think you misunderstood the question. Loctite locks nuts and bolts in place, I need to be able to change their position.



Nick - A nylon locking bolt is a good idea. I’ve actually been playing with some here and for the cam levers I think that they will do the job but for the part not so much, it would be too stiff to turn easily with the small thumb wheel attached.



To be clear this part is an M6 bolt, 100mm long, passing through a 13mm square aluminium bar.



RM-MN - This sound interesting I’ll have a play and see how it feels but ultimately I need a permanent fitting of some kind.

 

[nautilus29]

Maybe a stiff spring. You could trap the spring with a nut so you can adjust the tension that it applies to your setup.

 

[Blogwitch]

Viagra works wonders for stiffening some things up, but that is a solution for something totally different.

Go with the nyloc nut and partially thread it from the steel part first with a tapered tap. By experimenting a little on depth of penetration from the steel to nylon core you sould end up with a nut that will still hold fast, but still allowing you to fairly easily adjust it.

OR

Another way is to put a normal nut into your vice and just put the squeeze on. Depending how tight you go depends on how little or much the nut goes oval inside. Again, trial and error should get you just the right amount of grip you need, usually for something you are trying to do, only a little squeeze should be sufficient.

Hope this helps

John

 

[yadnom1973]

The spring is an interesting idea, something to put the whole thing under tension might do the job.

The nyloc nut is a good solution for the cam levers but there is no place to put a nut on the part that has the long bolt passing through it and is screwed into different positions. Maybe if a nut was somehow attached to the part but I cant see how I would attach it.

Putting the part that the threaded bar passes through and squeezing it slightly out of shape sounds like a possible solution, bit scary but I’ve a few spares to practice on.

 

[bazmak]

If you have room make your nut with a grubscrew to nip on the thread

 

[kiwi2]

Hi,
I had a bit of trouble figuring out how to sign in. Who would have thunk that the sign up button is the way to go.
If you want to stiffen up the action of the screw, drill and tap a 3mm hole in the side of the square aluminium through to the m6 screw. Cut a short length, (say 2-3mm) of 2mm nylon strimmer line and put it in the hole followed by a 3mm grub screw. You can infinitely vary the stiffness of the bolt by tightening the grub screw.
Eccentric Engineering use this arrangement on their Acute sharpening system and it works well.
Regards,
Alan C.

 

[yadnom1973]

The Nylon Locking nut has been the solution for the cam levers. The part with the threaded bar was trickier but a M3 grub screw to push small length of nylon wire onto the thread inside the hole sounds like the solution I was looking for. Thanks to everyone for the advise and help and especially to Alan C for this clever solution.

 

[Brian Rupnow]

You can buy nylon grub screws. One of them screwed into the threaded portion of the part which holds the screw at 90 degrees will serve that purpose very well.

 

[WOB]

WOB - I think you misunderstood the question. Loctite locks nuts and bolts in place, I need to be able to change their position.

See Loctite 222MS. It's designed for adjustable screws.
Also https://www.vibra-tite.com/threadlockers/removable-reusable-threadlockers/

WOB

 

[Wizard69]

There are a number of ways to do this.

The plain old lock nut / jam nut is often ideal.

You can also buy or make threaded split collars that will lock to threads. To prevent rotation the collars can be bolted or even welded in place.

Nylon face set screws can work but in my estimation a thick nylon plug backed by a set screw works better.

A cotter can be threaded an thus secure the bolt. This assumes you have room for a cotter.

Im not sure about this device but sometimes an anti rotation device, a pin or Rod, can keep the rest of the mechanism from nudging the screw.

Another option is a ring or bar that locks against a nuts hex or the bolts cap. Tedious and it limits you to fixed fractions of a rotation. In some places these are referred to as keepers.

You could always take the route of aviation and drill a hole and tie everything together with wire.

There are some other crude ways but hopefully you have some good ideas.

 

[Herbiev]

I just wrap teflon plumbers tape around the thread

 

[yadnom1973]

Yes there are some good ideas. I’ll have a look at the Teflon tape though I fear it may wear away. I’ll have a look at the nylon grub screw too. To be clear I don’t want to lock this just stiffen it. WOB, Loctite no matter how weak, such as the purple one, will lock the thread and when its turned will be broken and the resistance will disappear but the second product you link, Vibra-Tite, is something I had never heard of and could be perfect for the job. It sounds, as you first post said, like it’s designed to do the job I’m asking. I’ll do some more research into this.

 

[goldstar31]

Such a fuss over what is really nothing!

An old blacksmith would simply distort the thread of the bolt by hitting it along a line with a ball pein hammer.

If that failed, one would use a bit of fuse wire.

Threads are measured with the three wire system on micrometers or were.

Dear oh, dear oh dear!!!!

Norm

 

[yadnom1973]

These adjustments back and forth with the knurled wheel can be over very small distances and may need to be done smoothly and with precision and they could take place at any point on the 80mm length of the bolt.

I did considered distorting the thread, not with a hammer but by applying an even pressure in a vice. However the result of my experiment felt like what it is, trying to turn a damaged thread, inconsistent and catching in places and I think it would deteriorate over time as it in turn damaged the threading in the hole and became loose.

With a central threaded bore and movement possible in both directions threading wire, like threading the nylon or fishing wire, may work but only till it fell out. I need a more permanent solution.

 

[goldstar31]

Perhaps you might consider screw cutting ?

 

[DJP]

A split brass nut that you can squeeze with a set screw would be my preferred solution if you need precision resistance along the full length of thread. Adjusting thread pressure over the life of the device sounds like a requirement.