Prevent adjustable threads from backing too far out - How? 4

[KegOBear]

I am designing a device that uses treads to allow the user to set variable distances from the source item by simply threading and unthreading a "bolt". The problem is, the user could potentially unthread it too far which could lead to damage and personal injury.

As you can see in screen shot below, we do not have access to the start of the threads on the "bolt" as it is being inserted in to a "helicoil" that is being inserted into a tube that blocks us from putting a nut, weld, or deforming the treads on the start of the threads. I was thinking of drilling a hole and inserting a spring pin into the bolt is smaller than the pipe's ID but larger than the "helicoil". The problem with that is it can easily go too deep and stop the threads from spinning freely.

Long story short, I want the green arrow to the maximum allowed distance. Any suggestions?

Thanks All!

 

[btrueblood]

Put a circlip (or a Smalley internal retaining ring) down the hole before installing the helicoil. Put a mating circlip slot on the end of the male threaded part, along with a conical feature to guide and expand the circlip as the male part is threaded in (obviously the end of the female hole will need clearance to allow the end of the male thread to push in and engage the circlip, and there needs to be a flat to hold the circlip flat and push it onto the male part). Downside is that this is not removable after the circlip engages, if that matters. Smalley has examples on their website.

 

[KegOBear]

Great idea! I am looking in to it now.

 

[KegOBear]

Again thank you for this. I looked on their website and I did not find the application you were referring to. I did contact Smalley's engineers. They too were not sure. Do you have examples of what you are referencing?

 

[hydtools]

Smalley refers to ID/OD locking ring.

https://www.smalley.com/blog/special-rings-self-locking-balanced-and-idod-lock

Ted

 

[hydtools]

Concept

Ted

 

[moa1]

If exterior tube wall permits access, this may provide a thread stop. Machine threads to produce sufficient bottom foot to engage roll-pin or grub screw? Good luck

 

[mfgenggear]

hole with cotter pin

 

[KegOBear]

You are awesome! I poked through this idea. We currently have castings that prohibit the threaded portion from becoming longer. So alas... your great idea won't work for us "as-is". (See top image below).

But... it may (may) be possible to install one of these rings before we thread it in. The idea is to possibly compress it down, run it through the threads, and have it expand on the other side where it blocks (or at least makes it stupidly difficult) to fully unthread the object again. The biggest concern is will the threads survive the first run through? We ordered samples and hopefully will be able to try soon. (See bottom image below)

 

[hydtools]

A round wire circlip may tend to cause less thread damage.

Ted