Here is an example of a non-shopsmith face plate. I don't recall where I got it but it is a cast iron version and as you can see about 120mm. It is quite heavy when compared to AL based ones.

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The face plate is sold to fit different lathe spindles by way of an insert. The green arrows point to 2 of the three screws that hold and align the face plate to that adapter.
When we flip it over you can see the adapter, via the blue paint brush handle. This is a 1" - 8tpi adapter but they had other common spindle sizes but none for the shopsmith.

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So to get it to fit a shopsmith you need yet another adapter. This is the one that I now use, it is about $60 but is far shorter then others that are on the market and has the set screw at the shopsmith angle.

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BTW shorter is usually better in terms of lathe use and chucks/face plates so the chucks like the nova ones with the internal adapters are preferred way to go.
Now when it gets put together it looks like this:

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When I got this face plate I had only my basic shopsmith to use so there were no worries about running it backwards, this adapter has no way of locking on other then direction of thread to shaft spin. Now that I have upgraded to the powerpro this set up can not be run in reversed direction. It will/could simple come apart........ so there are down sides beside the extended length issue.
Ed