Project on a miniscule budget

Here's one to challenge all of you!

I need to put a 0.1875" square hole along a 1.25 inch length of a
0.250" square BMS bar. I need this hole to be a lapped or precision
fit on 0.1875" square bronze slipper. Fabrication using silver
soldered joints is a possibility but so far I have not been able to
produce these components with the fine finish I need for the job...
An EDM machine came to mind and I would like to have a go at making a
simple one if that's possible.
I am retired here in the UK and have little spare cash but as an ex
audio engineer and film sound recordist I do have some knowledge of
electronics.
I know there was a circuit for a very simple machine in Model
Engineer magazine many years ago (1970's I think) but tracking the
issue and a copy down has been fruitless so far even through the now
owners of the publication.
I believe the designers name was Roy Amsbury who worked for Rolls
Royce in Derby but I have been told he passed away some years ago.
Just wondered if anyone has a simple EDM machine design that they
might be prepared to let me have. Could be an interesting project to
pass the time away with.
Regards to all
Paul Miles.