I havn't bought anything the reason i asked was that 8mm seemed a bit small for a large machine. i can twist steel with a impact wrench of that thickness.

ok so it looks like its back to making the rack and pinion design.

need to find a engineering company locally to cut the side plates and swing arms. (once i have the design finalised)

hopefully you can make out the idea for the pressure adjust on the rack and pinion. it is early stages but closer than most.

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the more i look into it, the more complex it is. not impossible though