I drilled a 1/8" hole and used a 1/8"x1" roll pin, it seems to work well.
Printable View
12.4mm. I just threw it together as a possible example. Nothing even printed or tested. It's for this hex adapter:
https://www.amazon.com/gp/product/B07V55PGQZ/
How does this look for placement?
It’s 3/16” from the top of the Dayton motor.
That will leave 1/8” from the top of the pin.
https://i.postimg.cc/4dfHCvp9/391-EC...E7275-D4-E.jpg
Printing up a hex version now of the clutch and assuming it looks good I will post it.