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ET: Engine (Twin) pressing pin into rocker bearing


charles d cannon jr

Active Website User
VOC Member
Looking for suggestions about how to do this because I have just ruined ANOTHER rocker bearing and rocker arm. I placed the bearing in a 1 and 1/4 in socket, pin hole vertical. The bearing is supported at four points by rim of the socket. I chilled the pin in the freezer, heated the rocker arm in boiling water, lubed with oil, and placed a flat plate on the protruding pin that had been inserted into the bearing hole and seemingly in the mildly chamfered hole of the rocker arm. I used a hydraulic press. Regardless, the pin scuffed metal out of the rocker arm hole and pushed it into the rocker arm hole, ruining the rocker arm and one side of the bearing. I don't recall such difficulty before and being the paranoid type wonder if the rocker arm holes are machined properly. Thoughts and prayers will be appreciated. Thanks, Charles Cannon
 

greg brillus

Well Known and Active Website User
VOC Member
Technically you should always put a slight chamfer (bevel) on the pin being pressed into the rocker and then ideally polish this chamfered edge........this applies to any shaft being an interference fit like a crank mainshaft or spindles into the timing chest. As you have found out, the edge of the pin will broach its way in taking metal with it and thus damaging the components. It's a hard lesson, but we have all done it.......... I was taught and reminded of this many times by one of the best old school machinists I have ever known, and a long time Vincent repairman.
 

vibrac

Well Known and Active Website User
VOC Member
That minute chamfer is all that is required i also add a bit of lanolin and press in with a sheilded vice without the chamfer I have seen the far end of the rocker shatter off
 

roy the mechanic

Well Known and Active Website User
VOC Member
Hydraulic presses have their moments, but this job should be done in the vice. This way you can feel what is going on (or wrong). Chamfer on the pin is good, A slight countersink where it goes will also help.
 

charles d cannon jr

Active Website User
VOC Member
Technically you should always put a slight chamfer (bevel) on the pin being pressed into the rocker and then ideally polish this chamfered edge........this applies to any shaft being an interference fit like a crank mainshaft or spindles into the timing chest. As you have found out, the edge of the pin will broach its way in taking metal with it and thus damaging the components. It's a hard lesson, but we have all done it.......... I was taught and reminded of this many times by one of the best old school machinists I have ever known, and a long time Vincent repairman.
Thanks!
 

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