Sorry, but you will need to convert to imperial units.
You need to get some 16mm steel, cast iron preferably to make a backing plate. I fitted a 160mm 4 jaw to my smithy.
I removed the chuck and measured the flange dimension.
Then drill a hole through the centre of the piece, put a bolt head behind the 3 jaws and tighten it up as tight as you can.
Now you can face it and turn down to size.
From here you need to machine a recess that fits the flange as tight as it can be. You only get one chance at this as if you undo the bolt, you won't be able to realign the part. You will end up with some stuff in the middle but it will fit in the spindle hole. Turn the part around and heave a big sigh when it fits on the flange!
So now the trick is to drill and tap the mounting holes ( M8 from memory). The hard bit is to get thes bolt holes in the exact position. After turning the practice part into a swiss cheese, I found the best way is to turn up a short centre punch to mark the position. First off punch some witness marks into the machine flange and mounting plate to keep it in alignment as you take it on and off.
So now, drill your holes and tap them under the mill making sure the tap is dead square. I did one hole at a time and mounted it back on the lathe before punching the next hole.
Ok, one side done. You then bolt the plate to the lathe and then you can face it and machine the boss to suit the new chuck. Most aftermarket chucks have front mounting bolts so it is easy to punch hole positions. Tap them and you are done!
Or of course you could order one ready to go from smithy!
Sorry I did not have any more photos but this should be enough to get you going!
