Hi All
I have a problem or perhaps many! The bottom line is I don't know the answer to even that first question!
I have opted to design my z axis through 4 * 8 mm rods placed in a rectangle around the perimeter of the router. The rods will be attached to the y gantry via bushes in drilled blocks and the whole z assembly will be screw driven.
I have bought bushes which appear to have a teflon inner coating and they are designed to take a 8mm rod. I have created soft metal blocks with a hole of 9.9mm diameter which is the outside diameter of the bush (after being gently squeezed as it is split down one side). I gently hammered the bush into the hole. It was a very snug fit. It did not appear to damage the bush. I have bought some 8mm silver steel rod which I have been assured is of good precision. The rod could not go through the bush freely and even resisted a hammer tap. Net effect ... inside coating of bush is now damaged.
This is a situation that is recoverable as I can drill the bush out (have already doen it once) and start again. If necessary, I can re-manufacture the mild steel block that the bush goes into.
My inclination is to now buy a 10mm drill bit and repeat the exercise on the premise that the bush will go in easier and the rod will slide easier. I might introduce issues of precision by doing this as the router will be in a frame that is less rigid than if I were to persevere with 9.9mm holes.
Frankly I am surprised as I thought an 8mm bush would have tolerance to take an 8mm rod. I understand I might have assumed too many things. I also might have damaged the bush by tapping it into the 9.9mm hole.
For those who have been down this path ....... what would you do now?
Cheers
Andy  |