It always amazes me the contraptions resourceful people come up with....
What you have is not acceptable but just how unacceptable it is will depend on a lot of things.
1.) What amperage circuit breaker is protecting the branch circuit?
2.) What size wire was used for the branch circuit?
3.) What are the electrical specifications of the equipment.ie..what does the manufacturer say is required for the branch circuit supplying the equipment?
The first thing that comes to mind is you have a 20 amp nema 6-20P connected or tapped, if you will, to a 30 amp cord and plug branch circuit. For cord and plug equipment this is not allowed.
If the welder came with a nema 6-30P it needs 10 awg branch circuit conductors on a thirty amp breaker. The planer is a nema 6-20P most likely. You cannot mix them if they are cord and plug.