How to bond plastic knob to metal screw?

[Piaw Na]

I broke the plastic knob on my truing stand (see attached photo). I have a replacement knob from Park, but am discovering that just threading it on doesn't work --- when I need to turn the shaft counter-clockwise it comes off the shaft instead of turning it. I've already tried red and blue loctite and those don't work on metal/plastic interfaces. Should I try epoxy next?

[Josiah Anderson]

The goal is to remove that threaded rod, right? I would try to find two nuts that fit on there and lock them together, like you would on a hub axle, and just use those to turn it. Alternatively you could wrap it in something soft (bar tape?) and turn it with vise grips or something. I don't think the broken plastic knob necessarily has to be involved in this process, unless I'm missing something, which is very possible.

Josiah

Missoula, MT 

Le jeu. 13 oct. 2022 à 20:53, Piaw Na <pi...@gmail.com> a écrit :

I broke the plastic knob on my truing stand (see attached photo). I have a replacement knob from Park, but am discovering that just threading it on doesn't work --- when I need to turn the shaft counter-clockwise it comes off the shaft instead of turning it. I've already tried red and blue loctite and those don't work on metal/plastic interfaces. Should I try epoxy next?

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[Josiah Anderson]

Oh, rereading I see now that you're actually trying to get the new knob to stay put. What if you used that same locknut idea, just with one nut pushing against the back of the knob? That would probably hold it on quite securely.

[Garth]

The Park TS-2 is your stand, yes ? (sorry I don't know your name as it isn't shown)

The logical first question is, How was the know attached on your stand to begin with ? And to follow that, how was it attached from the factory ? 

According to their parts diagram the knob is held in place with a locknut to begin with. The pdf parts diagram shows it, and the video shows the guy actually installing the knob on the shaft with the locknut. 

I don't know the hi-story of your stand, but regardless, it is supposed to have a locknut. Either you have one or you don't. If not you have a suitable one laying around, or go to the local hardware store. 

https://www.parktool.com/assets/doc/product/TS-2_instructions.pdf

https://www.parktool.com/en-us/blog/repair-help/ts-rk-installation

[Piaw Na(藍俊彪)]

I do have the locknut, but it doesn't help. It keeps the knob from turning clockwise once it's snug against it, but counter-clockwise (the unscrewing action) doesn't work.

On Fri, Oct 14, 2022 at 1:31 AM Garth <gart...@gmail.com> wrote:

My first question then is "how was the knob attached to begin with from the factory ?" 

According to the photos, that style of knob was used on the TS-2, this is yours yes ? (Sorry I don't know your name as it was not included)

So, ever inquisitive, whenever it comes to parts, I always refer to original parts documents. According the stock photos and parts pdf, there should have been a locknut for the knob to begin with.  https://www.parktool.com/assets/doc/product/TS-2_instructions.pdf

You may have a suitable nut on hand as Park likely uses common SAE threading. If not you could contact Park and maybe they'll send you one or just go to the local hardware store. 

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[Eric Marth]

I'd try something like red Loctite first. Easy to find, easy to apply. 

If that doesn't work you might try looking for a more robust replacement thread-on knob that has a set screw built in. Find our the pitch of your metal thread and check out McMaster-Carr for "threaded hole knobs." 

[Piaw Na(藍俊彪)]

Already tried red loctite. Doesn't work.

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[Garth]

Did you watch the video to see exactly how Park does it ? 

Are you sure you're not bottoming out the knob first before you tension the nut against it ? (They say leave 8 threads after the locknut is threaded on.)  

Follow the video, that's all I can say. If you say that doesn't work then that doesn't make sense as that's the way it comes from the factory in the first place. 

The obvious question then is why isn't or wasn't yours held in place with the locknut before it broke ? 

How was the knob held on yours ? 

How did it break anyways ?  

Have you ever called Park to ask for help ? I'm sure you wouldn't be the first to run into a seemingly insurmountable issue with the knob. 

[lconley]

Have you lubricated the other items along the threaded rod to reduce the amount of torque required to rotated the rod? Boeshield would be good for that. Lubricate the shaft (except for the knob/locknut) and the tighten the locknut real good against the knob. If that doesn't work, the just keep a wrench handy to turn the locknut against the knob when wanting to rotate the shaft the opposite way from the knob.

Laing

[rlti...@gmail.com]

I have used JB Weld on a number of metal to non-metal interfaces and it worked really well. I can’t recall any failing. This is the standard JB Weld that has black & white materials that you mix together to get a gray material.

Robert Tilley

San Diego, CA

Sent from my iPhone

On Oct 13, 2022, at 7:52 PM, Piaw Na <pi...@gmail.com> wrote:

I broke the plastic knob on my truing stand (see attached photo). I have a replacement knob from Park, but am discovering that just threading it on doesn't work --- when I need to turn the shaft counter-clockwise it comes off the shaft instead of turning it. I've already tried red and blue loctite and those don't work on metal/plastic interfaces. Should I try epoxy next?

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[Piaw Na(藍俊彪)]

I spoke too soon. Overnight, the loctite cured and now I can turn it (with a ton of effort, but it works!). Now I can build up my wheel.

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[David Person]

Epoxy

[Bill Schairer]

Sounds like you need to lubricate that shaft.  It shouldn't take a ton of effort to adjust.  I have one of those.

Bill S

San Diego

[Garth]

I forget to add what Laing already mentioned, I figured the knob was loosening because the shaft wasn't moving freely enough. Hence, people overtighten the knob and break it in trying to compensate for the resistance in the main shaft.  If lube isn't enough, a new main shaft kit would apply.

[Bill Schairer]

Oops, clean and lubricate the shaft AND all the other joints that are supposed to move when you turn the shaft.  Just do everything.

Bill S

San Diego