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Bushing with grooves. Main purpose?

Bushing with grooves. Main purpose?

Bushing with grooves. Main purpose?

I have a butterfly plate in which a shaft runs through so it can open and close the plate. Occasionally, the shaft cause damage to the housing of the plate. Therefore, a bushing that will be used as a sleeve will be inserted in the butterfly plate. The O.D. of the sleeve has 5 grooves. Structural adhesive will be applied on the O.D. of the sleeve and the sleeve will be inserted into a butterfly plate. A shaft will run through the sleeve. What is the purpose of having those grooves for the adhesive? This will be a slip fit installation.

RE: Bushing with grooves. Main purpose?

Usually the grooves on a plain bearing are to facilitate the movement of lubrication across the bearing surface. I suppose in your case the grooves would hold extra adhesive as well. I doubt the grooves will add much holding power provided there is already enough space around the bushing for the adhesive.

RE: Bushing with grooves. Main purpose?

I'm guessing the unspecified structural adhesive is expected to bond only weakly to the unspecified bushing material, so extra surface area is provided to compensate. That also assumes that the adhesive will bond satisfactorily to the material in which the bushing is to be installed. If the shaft rotates with the butterfly, I'd expect the bushing to be installed in the housing, not in the butterfly, but perhaps I am misunderstanding your geometry.

Mike Halloran
Pembroke Pines, FL, USA

RE: Bushing with grooves. Main purpose?

Right, there is a slip fit. the space between the butterfly plate and sleeve is about 0.0005 to 0.001" in total diameter. The bushing will be coated with adhesive and inserted inside the butterfly plate. The shaft will run through the butterfly plate with the bushing installed. There will be a tight fit regardless, the adhesive is just there for extra bond. But I wasnt sure why there are grooves. I am guessing to add more surface area thus allowing to bond to more surface creating stronger bond?

RE: Bushing with grooves. Main purpose?

Adhesive bonds are subject to many different stresses. In the joint you describe the main stresses will be caused by cure shrinkage and CTE differences between materials (bushing, adhesive, and housing). The grooves create a mechanical lock that will hold the bushing in place even if there is no adhesion to the bushing. Also the bondline is far thicker in the groove than in the thin gap making the adhesive layer more compliant and less sensitive to dimensional changes due to CTE. If the bushing shrinks by 0.001", the adhesive strain in in your case will be over 100% with a smooth bushing. In a groove that is 0.01" deep, the adhesive strain is only 10%.

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