Not quite sure what you are saying. Do you mean the pitch circle diameter (PCD) of the coupling bolt holes? Given the holes will be 1 mm biger than the coupling bolts there shouldn't be a problem. You could always take the gearbox flange off and get the new flange drilled to match (45 degrees out, in the solid metal).I now facing one more problem. I can't find the right size new coupling online! My coupling flange diameter is 120mm. The gearbox flange diameter is 121mm. So I think it should be 4 - 3/4 inches will fit. Not see a fit one online yet! Headache!
Not really interested in your "arse", or indeed being a smartarse. Was just trying to give some helpful input to the OP.Tapered key my arse.
If the engineer asked the workshop to make a joint like that he'd get told to bugger off.
A towel would be more use as the terry will hold more water, or buy a fire blanket and use that.If you do grind, on top of the good advice above get a old sheet or similar, soak in water and cover the surrounding area where sparks will land. Not only to minimise fire risk but hot sparks will embed into the grp and then rust making an awful mess
Were the grub screws short , as I remember on some joints , people put one grub on top of another , have you tried your allen key in the hole to see if there is another in there . Sorry someone mentioned early.The shaft is parallel not taper, and the coupling is about 15cm in length. I think it won't likely pop out like a bullet. It will likely need all the way pull through 15cm under that tension.
Since I already broke the puller, so I don't dare to try to use the gearbox to pull it. That will be one more headache if the gearbox broke because of that.
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Hard to see how big the key is, but could you drill and tap it then screw in a length of studding long enough to improvise a slide hammer? You may need to heat the coupling while hammering. If it doesn't come out, there's nothing lost but some time.The key is just a normal square key. Not looks like any hidden trick in there. I can see the keyseat hole from behind the coupling. Just can't remove the key anyway.