I tried to make a jig that can do high precision dowel hole machining with hand drill without using drilling machine.
(We use a hand drill in the example, but if you have a drill at hand you should use it.)

【parts】
Metallic spacer of drill guide
https://amzn.to/2RvqFs7

Jig plan convenient for woodworking
[Plan List]
https://jsk-koubou.stores.jp/

This jig can also be applied to T junction which was impossible with conventional simple dowel jig. Or, it is a way of making it applicable to all dowels processing.