Instrument Cluster Screw Hole Repair - Can it be done?

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1973 Convertible Q code Ivy Glow Auto C6
I'm continuing my project of refurbishing my interior (and a bunch more) and ran into an unexpected problem on my project. When taking the Instrument Cluster apart, I found two places where the Speedometer and the Fuel Gauge attach to the cluster where the screws were barely hanging on. When I got it apart I found that the plastic had been cracked pretty severely on two of the screw holes.

I was thinking of adding some type of glue to fill the gap where the plastic has separated since I can't really compress it? Any thoughts or experience on this would be appreciated.

Bob
 

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An ABS adhesive would probably work. Check the plumbing dept at Home Depot. You could probably clamp it back in place. If it was me, id do that then find some styrene rod at the hobby shop. Drill down the screw hole so the rod fits and glue it in. Cut flush and redrill for screw.

I've fixed similar things on my Opel, but the screw bosses were not connected to anything, so I could slide brass tubing over them.
 
If you fill it with baking soda and add crazy glue ( perhaps 1/2 baking soda, then crazy glue, then more baking soda and crazy glue) you will fill the hole up to be solid, then just drill a pilot hole and put screw in. Tape off crack before baking soda so it does not spill out.
 
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I'd do the superglue+baking soda combo. Lots of videos on the youtubes about how strong that one is.
My concern would be after you fill it in and drill it, then try to run the screw into the new hole, some other part of the 50yr old plastic may crack. So don't drill the pilot hole too tight.

I'd probably drill it and tap it. Then use a screw the same thread pitch as the tap, rather than some coarse thread screw we commonly see used on these parts.
 
As suggested above, I will use ABS pipe solvent cement from the hardware store. We are lucky that ABS can be remelted with solvent. For better results, if you can find extra ABS from elsewhere in the panel you can melt it with the solvent and then fill the hole with it. You are basically making a paste to use as filler.
1723753557379.png1723753612761.png
 
tony-muscle said:
As suggested above, I will use ABS pipe solvent cement from the hardware store. We are lucky that ABS can be remelted with solvent. For better results, if you can find extra ABS from elsewhere in the panel you can melt it with the solvent and then fill the hole with it. You are basically making a paste to use as filler.
View attachment 91999View attachment 92000
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We use this often in the 3D printing hobby. Just acetone and scraps of ABS dissolved in a glass jar.
Legos and barbie dolls are another source for ABS, supposedly. OP may go rob a gray lego out of his kids' bucket and dissolve it with acetone to make a filler paste. :D
 
The black ABS cement is basically ABS plastic dissolved in solvent and dries to ABS plastic. Because the split section is hidden from view you can just fill in the hole with the black ABS cement, wait for it to dry, and drill it to size for the original or a sheet metal screw.
 
giantpune said:
We use this often in the 3D printing hobby. Just acetone and scraps of ABS dissolved in a glass jar.
Legos and barbie dolls are another source for ABS, supposedly. OP may go rob a gray lego out of his kids' bucket and dissolve it with acetone to make a filler paste. :D
Click to expand...
Only an uncouth barbarian would sacrifice Lego! Barbie is fair game, tho....
 
Don C said:
The black ABS cement is basically ABS plastic dissolved in solvent and dries to ABS plastic. Because the split section is hidden from view you can just fill in the hole with the black ABS cement, wait for it to dry, and drill it to size for the original or a sheet metal screw.
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Masking tape the outside so the cement stays inside.
 
The black ABS cement is fairly thick and designed not to run, so is unlikely to run out of the gap. In fact, I would use a flat blade screwdriver to force some into the crack. It'll also need to be forced into the screw hole.
 
For me, I'd weld it. Why, because that's the sort of work I did and have the equipment to do that. But, there have been some suggestions I did not know about. The one benefit of ABS is that it is a solvent based plastic and much easier to repair. Plastics like PP or PE are a different story. So it's probably a good thing that car manufacturers chose a cheap plastic to make these parts from.
As for this scenario, I'd go with the black ABS cement as it will have similar properties to the original material. The baking soda and crazy glue might be on the hard side to form a good thread. That's speculation on my part as I've not tried that.
 
Thank you so much for all your help and advise! I never thought about the ABS plumbing cement and will try that and see how it goes. Seems less intrusive and like mentioned perhaps a little softer for the screws to cut into. I'll play with it thanks to you all's input and I feel much more confident with it. Once it's done, I'll post a picture and share how it worked.

It'll be awhile though, because in taking these gauges off my cluster, I found my Fuel Level Gauge had a defective threaded post/stud and I twisted the whole post, no doubt damaging it. So it's off to Rocketman to try and fix & calibrate this. We're so fortunate to have our great vendors!

If interested, here's a picture where you can see the threads are at an angle versus perpendicular to the shaft???
 

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cv_72mustang said:
I used something called PC7 long ago. Used it to fill carb and 2 cycle ports. Think it might still be available. Course the 'formula' might have changed to abide by toxicity regs.
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This stuff looks incredible! Thanks for sharing this idea. Never heard of it, but now I have to get some and try it. Not sure I want to go with this hard of a substance for my plastic Instrument Cluster though. When looking it up to learn about it, I found this video of a guy that used it for a rust repair. He say's he's used this stuff for like 30 years in the application shown in the video successfully??

https://www.google.com/search?q=pc7...ate=ive&vld=cid:d01c819d,vid:6UMfwSp3zNE,st:0

Thanks for introducing me to this stuff! Bob
 
Something to consider when fixing damaged holes...the 'filler' should be no harder than the material you are fixing. The smaller the repair, the more important this is. If the material you are trying to drill into is harder, the bit may tend to slip or drift into the softer material and either end up with a hole in the wrong place or it might just destroy it.

I've also coated the appropriate sized screw with grease and embedded it into the repair material while it is uncured. When it has set up, the grease allows the screw to be removed leaving preformed threads. Doesn't work with anything the grease would affect.
 
detritusmaximus said:
Something to consider when fixing damaged holes...the 'filler' should be no harder than the material you are fixing. The smaller the repair, the more important this is. If the material you are trying to drill into is harder, the bit may tend to slip or drift into the softer material and either end up with a hole in the wrong place or it might just destroy it.

I've also coated the appropriate sized screw with grease and embedded it into the repair material while it is uncured. When it has set up, the grease allows the screw to be removed leaving preformed threads. Doesn't work with anything the grease would affect.
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Perfect! Thanks for this. You've been sooooo helpful.
Bob
 
On my center console and a few other places, I roughed up the hidden places, coated with epoxy and laid fiberglass or carbon fiber resin and top layered again with epoxy….works great for larger and structural repairs…
 
here is a plastic welding kit I purchased a few months ago. I have yet to need to use it. But, the "Chichanic" (YouTube Channel) has used it and showed some examples of what she has done to repair roken or cracked plastic parts with it. I saw enough to know that if ever again I have a broken item made of plastic I will be effecting its repair using this kit. I may do some addition filler using baking soda and crazy glue or ABS cement. But, I feel a physical (re)bonding of the plastic material, especially with an inserted steel reinforcement piece, will do far better of making a permanent repair as opposed to a chemical bond. It is worth a shot.

https://www.amazon.com/gp/product/B08ZCQRVJ2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
 

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