Supply and demand. To find out what you are worth you have to throw yourself onto the market. If you want to stick with the security and convenience of the job you have, your current worth is what they are paying you.
Did this company pay you to do your degree? Do they need your expanded skill set? Normally completion of higher education requires a change in employer to cash in on it. If you are a skilled machinist, you should now be looking for a new challenge. No one will ever be able to take your trade from you, but if you keep doing what you can already do, the income curve will be flat.
Generally a guy with a degree plus real practical shop floor experience has the potential to really move up and make good money. Often you have to take a step backwards at some stage in your career for the move from shop floor to office (and many don't want to), but that is where the decisions are being made and pay is set.
I served my time as an aircraft mechanic in the air force (NZ), then worked line maintenance at an airline and got licensed. Took a pretty bit pay hit to move into the airline engineering office to be a seat and interiors engineer (crappy job), it paid off cause six months later one of the engine guys moved on, and I easily got the engine specialists job. Six years later I move to the authorities as a certification and airworthnes inspector. For me a dream job, good pay, lots on responsibilty, get out and about, travel, continuous further education etc.
Where do you want to go?