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Life is full of surprises (bolt strengths)

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  • Life is full of surprises (bolt strengths)

    Todays main job was dismantling part of a marine gearbox.
    The propellor shaft coupling has to be pulled off its shaft, the coupling is 10" dia & the shaft about 3.5", keyed, parallel.
    I tried my 10-ton hydraulic puller, it wouldn't look at it. Tried heating the coupling & then cooling the shaft with a freeze spray, nothing doing.
    It would have been a nightmare to try to get the assembly into a press, plus I don't have one suitable. Next step was to cut a disc of 1" thick steel plate, & drill six 18mm holes to sorrespond with the holes in the flange. Then six well-oiled M16 high tensile set bolts & nuts through the two sets of holes, with the plate bearing on the end of the shaft. By going round the bolts several times with an impact driver, eventually the thing started to move. After a while the shaft end came flush with the coupling face, so some packing was needed. The shaft end is drilled & tapped 5/8" Whit, so I found an HT setscrew & screwed it in with 1/2" of exposed thread, there then being about 5/8" of thread engaged. I was a bit concerned that this 5/8" thread might strip, with the full force of the six M16 bolts applied to it. NO problem there, but what took me aback was that the exposed part of the bolt had very neatly compressed in length, and swollen in diameter by about the amount of the thread depth. Perhaps I shouldn't have been surprised, but I expected the thread to fail before that happened.

    Anyone fancy having a stab at what compressive force six M16 bolts can produce, with a 1/2" impact driver run to its limit?


  • #2
    About 4 to 5 tons each.
    Free software for calculating bolt circles and similar: Click Here