Strength of Aluminium base plate
I have a fixture designed in which the base plate is Aluminium. Two clamps (diagonally oppiste) will be used to hold the job. Clamping is done using M6*0.75 Allen bolts. Aluminium base plate is of 20 mm thick, in which 10 mm tapped hole is provided for clamping. Clamping of allen bolts are done with hand tightening, which equals to 60 LBS torque. After two or three times of using the fixture (unclamping, fixing new job, and clamping) I find that the tapped holes in aluminium base plate got loosened. Is there any basic design problem in this fixture? Can anyone help to resolve this issue?
Thanks and regards,
GM