| [GMCnet] Rear panel screws [message #336624] |
Sat, 01 September 2018 19:06  |
JerryW
Messages: 256
Registered: August 2018
Karma: 1
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I had some off line questions about where to find the special fasteners for the rear panel on our GMCs.
They are called thread forming screws for brittle plastic. Sometimes also called hi-low thread screws. In McMaster Carr they are listed:
https://www.mcmaster.com/#high-low-screws/=1eeyu56
If you look at the OEM fastener for the rear cap you will see that it is a screw with both a high and a low thread and a blunt nose. These are designed to cut threads in the resin binder in fiberglass, SMC, and other brittle plastic materials when the pilot hole is the same size, or ever so slightly larger, as the root diameter of the screw.
The two piece fasteners some suggest for this purpose are generally called threaded inserts. The insert part only has a single height, segmented thread. Those are designed for use in the cross grain of wood where the segmented teeth will cut into the wood fibers and hold fast. They cannot be used in end grain very successfully because they will just tear out the end grain if over stressed. They may work for a while in fiberglass or SMC but over time they most likely will fracture the binders in these brittle materials and you will be right back to redoing them again.
If the holes in the SMC on your GMC body are damaged or enlarged you need to fill and redrill them before inserting the proper hi-low thread screws. You can use different sizes of these special screws anytime you fasten something directly into the SMC skin on the GMC.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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| Re: [GMCnet] Rear panel screws [message #336625 is a reply to message #336624] |
Sat, 01 September 2018 20:44  |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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Thank you for the info although I'm a bit confused on which screws to order. The screw I removed measures about 7/16"in dia and about 1" long which seems to be quite a bit larger than the ones MC sells-or am I looking at the listing wrong? Thanks for any clarification. BTW, my GMC is a 1977 vintage. Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: [GMCnet] Rear panel screws [message #336626 is a reply to message #336625] |
Sat, 01 September 2018 21:16 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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Hi Hal, there is a product that is an epoxy thread repair that you mix up and put in the hole then it has a release agent you put on the OEM screw and install it snug. When it sets up you can torque it to spec. Seems it was just called thread repair?
Hal StClair wrote on Sat, 01 September 2018 21:44Thank you for the info although I'm a bit confused on which screws to order. The screw I removed measures about 7/16"in dia and about 1" long which seems to be quite a bit larger than the ones MC sells-or am I looking at the listing wrong? Thanks for any clarification. BTW, my GMC is a 1977 vintage. Hal
C. Boyd
76 Crestmont
East Tennessee
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| Re: [GMCnet] Rear panel screws [message #336629 is a reply to message #336626] |
Sat, 01 September 2018 22:46 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Hal & Chuck
One thread repair product is "Form A Thread" by Loctite.
Dennis
C Boyd wrote on Sat, 01 September 2018 21:16Hi Hal, there is a product that is an epoxy thread repair that you mix up and put in the hole then it has a release agent you put on the OEM screw and install it snug. When it sets up you can torque it to spec. Seems it was just called thread repair?
Hal StClair wrote on Sat, 01 September 2018 21:44Thank you for the info although I'm a bit confused on which screws to order. The screw I removed measures about 7/16"in dia and about 1" long which seems to be quite a bit larger than the ones MC sells-or am I looking at the listing wrong? Thanks for any clarification. BTW, my GMC is a 1977 vintage. Hal
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Rear panel screws [message #336630 is a reply to message #336629] |
Sun, 02 September 2018 08:44 |
GMC.LES
Messages: 505
Registered: April 2014
Karma: -2
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Senior Member |
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Jerry,
Thanks for bringing those off line (back channel) questions back on line. I have never understood the logic behind people seeking info “off line” when a discussion on the subject is occurring on line. If those people need to ask their question, there is a good chance others might benefit from the answer. I doubt anyone would complain about the additional traffic it might create as we are all here to learn, help, and share.
When an answer is provided off line, it serves to help that single person at that instant. That info never enters the data base we call the gmcnet archives, and it often becomes lost and forgotten. If shared online, it remains available through a search for as long as the gmcnet archives remain alive.
Please don’t take my rant as a complaint. I’m just trying to point out how we all can help improve the function and value of GMCnet.
Les Burt
Montreal
'75 Eleganza 26'
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