why not make an adaptor to fit over the existing spikes as said above like the one in my rough drawing turning a vertical mount into a horizontal mount then just bolt the weights either side of the arm
Hi,tryed the chap with a hammer and no movement,so l think if l get the arm off and turn it round l'll get a better hit at it and get them off,my plan is lve got a couple of plates 6mm x 280mm diameter,put a hole in the ctr and put it over where the weight sits and tack it on so when l sit weight lifting weights on top they'll sit flat and square an not slide round the end.
You'd still be better using a tube. Weld a tube with an I.D just large enough to slip over the spike to the circular plate/disc, with a corresponding size hole in the centre and slip it over the spike. That way, you can add height, and as you've already found out, the weight spikes are designed so that when you slip something onto them, it stays there. You really shouldn't need to weld to the arm at all. You're merely limiting yourself if you do that. Keep alterations so that they're easily removed and changed/adapted, if necessary.