Return to the Metalworking Forum | Post a Follow-Up

 o
Screw thread question

Posted by hald (My Page) on
Sun, Jan 4, 09 at 1:07

Does anyone know of a product, somewhat like Locktight, that I can put on machine screw threads to make them tighter but still movable?

I am trying to correct a problem I'm having with one of the tuning keys on a folk harp. The key is too loose and will not keep the string in tune. Thanks in advance -
hald


Follow-Up Postings:

 o
RE: Screw thread question

Its possible to keep a machine screw from loosening by first degreasing or cleaning the threads, and then coating them with oil paint, your choice of color. With the paint still wet, assemble and tighten to whatever position you desire. The paint will dry, and help keep the screw in place. However, paint will not stand up to repeated movement of the screw, it will gradually wear off. So, this is not a permanent solution, it will just get you by for a while.


 o
RE: Screw thread question

I'm not familiar with your folk harp....like Eric said, eventually whatever you put on will wear off in the long run.
How often do you turn?
I'm thinking of silicone, you can experiment on some other screw first and see.
The screw goes into a nut right??...I'm thinking of a nylon lock nut, these can hold fairly long.
What I have done in the past,...drilled a small hole true the nut and pushed in a nylon pin tight, this pin will
rub against the thread, thus creating friction and nut staying put.

Or something what has tension, ...the screw could be split in that section where the mating part goes.
Splitting in half with a very fine slitting saw about half thickness of a hacksaw, [machine shop] this section then
slightly spread open, this makes tension, ... perhaps the nut could be cut open one side too and pushed together slightly what creates tension.

Konrad


 o
RE: Screw thread question

Thanks for the information. The problem I'm having is a bit different than what I first thought. The metal pin that holds the string end is tapered and fits into a tapered hole in hardwood. From other forums I learned my problem is common. I will try the oil paint suggestion first.

Harps are tuned often, daily or more. On my folk harps I usually tune a couple times during practice. Tuning is a huge issue because harpists spend so much time tuning. From other forums I read that designing and installing the tuning mechanisms is challenging. My harp maker has changed mechanisms since my harp was built.

An irony is that I traded in a harp with the same, though more severe, problem, because it had slowly progressed to being impossible to tune.


 o
RE: Screw thread question

Since the threads are tapered, it's a little more complicated. I wonder if you could use PFTE thread tape, like plumbers use, or pipe dope?

Is the tapered hole directly in the hardwood, or is there a metal insert? Unless there's technical reasons for it being done that way, it sounds as if the way harps are made hasn't changed for centuries.

If you could afford to, and there was no technical reason not to, the ultimate answer would be a metal insert that was threaded inside, which would give you more durability.

There is also an automotive product called a "helicoil" which is a very durable stainless steel spring-like product which replaces worn-out threads and becomes the new thread itself. A tapered thread might not be possible with helicoil, your best bet is an epoxy glue type thread repair such as:

Here is a link that might be useful: Permatex stripped thread repair


 o
RE: Screw thread question

Hm...perhaps Teflon..I would give it a try.

Konrad

Here is a link that might be useful: Teflon Tape


 o
RE: Screw thread question

Yes teflon is the right choice.

Here is a link that might be useful: concrete bolt


 o
RE: Screw thread question

lol:)

The metal pin that holds the string end is tapered and fits into a tapered hole in hardwood. Yea, I suspect it's been this way for centuries.

Teflon tape sounds like a good try! I'll report back.
Thanks!


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Metalworking Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here