| [GMCnet] Rear panel screws [message #336624] |
Sat, 01 September 2018 19:06  |
JerryW
Messages: 256
Registered: August 2018
Karma:
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Senior Member |
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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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