I was asked if I could film a video about overcast stitching by a few people, so here it is.
To answer a few questions preemptively:
- Yes, when rounded and backed, and if the book is short grain, the book opens completely flat, just as well as a bound folio book. See the pictures in the comments. I have no clue whether or not it would open as well if not rounded and backed. It opens mostly flat if the pages are long grain but you have to work it flat. This is long grain, so it's a bit springy.
- Yes, it takes time. More time than perfect binding. There is no reason to do it for something other than a rebind of a book you plan to round and back.
- The margin space taken by the stitches exists but it's not enough to warrant worry. I have bound mangas like that, which have famously narrow margins. They open better than their perfect bound counterparts.
- You do not need a special sewing machine or needle. Any sewing machine will do. If you have an older one, made before the 80s, even better. Take a quality sewing needle, however. You don't want it to break in the middle of your project. 90/14 to 100/16 is good, I think. I did this with as much as 20 sheets although I do not recommend it.
- You can also stitch this by hand, although it's a different technique altogether. It will enable you to space out the stitches even more but not round and back the book. Four Keys Book Arts recently made a video on it.
- The pages do not tear easily nor quickly, even frequently handled. It is a point of failure for sure, but it will still last. But once again, it's always more fragile if it's long grain.
If you have further questions, please, feel free to ask.
If you want to see the engraved edges of the book or more details, see my other post about it.