Add friction to threaded rod

[Asellith]

I am working on a project that is giving me headaches. I have a threaded rod with an aluminum tube around it. This creates the part I need but I have run into another design issue. When the two parts are screwed together orientation matters. However as I make additional pieces they are not lining up with each other like I need them. A simple fix would be to add friction to the threads so that it will hold the parts from rotating but not require over tightening to position them properly.

Any ideas on how to get nuts to stop on a rod but also be reusable? Most solutions work once and are more permanent thread locking. I need something like a nylon lock nut but on the threads not the nut.

I got a rubber grommet to work but it is way to big and ugly. Gonna try a bit of heat shrink tonight.

This is the first prototype of the project: http://www.corseceng.com/blog/2011/4/8/workbench-update-introducing-the-omnistand.html

[dunk]

have you considered an all nylon nut which you tighten against the aluminium section?
they come in fairly un-obtrusive clear nylon colour and are fairly thin.

alternatively you could add a grub screw through the aluminium component at right angles to the tread.
on the down side this would greatly add to the manufacturing time/effort as you would have another precise hole to drill and tap.
better still would be a nylon grub screw so it would not damage the main thread if over tightened.

another idea,
what about using keyed bar for the round section. this has a rectangular slot running down it's length.
after you cut the threads in the end of the bar, fill the slot with a strip of nylon that has been carefully cut to just touch the tread.
the down side of this is the keyed slot will run the entire length of the bar, messing with your aesthetics. but maybe you could fill the entire slot with the nylon and use heatshrink over the visible part to hold the nylon in place....


dunk.


[edit]
actually, now i think about it,
why not just make the whole bar from nylon and source a *slightly* oversize die to cut the threads? (i presume these exist...)

[MikeK]

Could you drill a hole into the threaded rod and insert a length of nylon screw?  It would help if you had access to a small lathe so you could machine the threads off of the nylon screw before you press it into the hole.

[Soeren]

Hi,

If you make the top part (that goes into the spaceship or whatever) without treads but with a tight fitting bushing made of synthetic rubber (like urethane), or make the entire top part in urethane and then keep the rod without the treads (but with a few mm of taper to ease insertion).
This way you will be able to get a friction fit that can be turned in any direction and still hold its position. It will be much cheaper to make as well.

Another option would be a bushing on the flat part of the stand and this will ensure a longer life, as 3..5mm acrylics are bound to chip and crack, sooner or later even sooner, from tension, when you repeatedly tension a screw into it.

[hopslink]

As an extension of Dunk's first suggestion. If you tap the "top hat" section slightly deeper then part it near the "brim" you will have your holder (top of the hat), and a matching jam nut with 'finger friendly flange'^TM (brim).

I suspect Soeren is closer to the money though.

[Asellith]

I need the threads on the top because the entire system is designed to take other components on top like the magnetic spheres and alternative miniature mounts. (for small fighters) The base also now has a threaded insert for plastic to minimize wear and tear on the acrylic.

I can't drill the rod or tap anything because I'm having trouble machining them by hand without screwing up. (my skills at machining suck)  I can't get perfect perpendicular rods for some reason even using my drill press as a guide. Also time is a big factor for me.

I've thought of a a nylon spacer glue in place at the top or some kind of washer. I'm experimenting with several thread lockers and sealants now. I'm also gonna look into some kind of soft tubing that I can cut really short and glue in place as a stop.

i could go with what I have right now and explain to the customer that they need to center their miniature when they attach it while it is on the shaft. that also means I need to be precise with my thread depth and insert placement. I have a mini cut off saw on order right now. When i get that in then I'll see how precise I can make these cuts and see what happens. How did I end up starting a company that requires so much mechanical engineering and no electrical engineering.... Someday I'll have the time to union the two and start promoting my erector set to electronics adapters and make a bunch of cool stuff with them. Then I'll get back to my roots.

[Soeren]

Hi,

When I need a semi tread lock in a hurry, I either cut an elastic band, screw what has to be screwed and pull on the free end for a close snip, or add a pinstripe of contact cement to the inside tread and let it dry.

Another way is to cut a slit through the rod (length-wise) and spread it a teeny bit for a friction fit.
Should be possible with your new equipment 

[Asellith]

I ended up putting a small #003 o-ring on both ends. It stretches enough to provide a good solid hold on the rod and gives me the friction hold I need. Cheap and easy. I love that combo. It doesn't look bad either. Once I get my saw in it should be really easy to put everything together.

[putz]

having little trouble visualizing but.... Rub a wax candle up and down the dowling. What ever nuts that thread on the dowling, just squeeze slightly in a vise, making the nut slightly out of round. i use the latter all the time and the effectiveness never wears out.

[Asellith]

This is what I went with for the final product.



It works great and looks cool.

Here is the full preview. Product is going into production now and will be available in a week or so.

http://www.corseceng.com/blog/2011/4/29/product-preview-omni-stand.html