[Sticky]  How To Become The Greatest Miner! [Miner Guide]
Take the job "Miner"
Purchase a Crusher, a Regular Conveyorbelt and a Refinery of the type of material you are mining or are planning to mine. [Use the builder tool]
Place the Crusher first, then buy the conveyor belt with the builder tool.
While holding the build tool, there should be a green circle on the crusher. Simply buy the conveyor belt and it will snap into place.
Do the same with the refinery on the other side of the conveyor belt.
Then buy a refinery crate and put it under the chute of the refinery (should also have the green circle for it to snap into)
Then start mining. You can do this one of two ways. Use your pickaxe (recommended at first) or buy a Mining Entrance and place it next to the ore/coal you want to mine and send the cart down (using "use" key) to do the mining for you.
Either way, take the ore you mine and drop it into a gravel crate (right click on it with the pickaxe multiple times to drop all ore or grav gun ore from the mine and drop it into the crate).
Once you have enough ore, you need to mine coal.
Buy a coal refinery and a normal conveyor belt.
Using your build tool, to place the normal conveyor next to the ore refinery you already placed (look for the green circle)
Now buy and place the coal refinery the same way at the end of the conveyor.
Now buy another refinery crate and place it under the chute for the coal refinery.
Your machine is complete (up to this point) and ready to start processing coal and the ore you have mined.
Now. go mine Coal.. lots of it. When you have at least 25-50 in a gravel crate you're ready to start processing.
Grav gun your gravel crates with the ore and coal and bump them into the rock crusher. It should start processing and kicking small gravel bits down the line. The ore and coal will automatically get sorted and go to the right machines. You can add other ore refineries the way you added the coal refinery to the line and even create more complicated machines with the various types of conveyor belts.
While you wait, go ahead and buy a Melter and place it near the conveyor belt system. It won't be hooking into anything, but you'll need room to be able to access both sides of it.
Once you have a decent amount of processed ore under the refinery, press your USE button on it to detach it from the line, then grav-gun it and put it into your Melter.
Do the same thing for coal, but you might have to add it to the far side of the machine. Either way all you have to do is touch it with the gravel crate.
Once the melter has enough ore (marked on the front of the machine) and enough coal (marked on the back) it should fire itself up and start smelting the ore into bars.
If not, then it should tell you what it's missing or needs more of. If you didn't have enough ore or coal, just go mine and process more. Make sure you put your refining crate back under the refineries on the conveyor belt first or you'll lose some of your processed materials.
When the Melter is done, it should drop 6 bars. You can place those in a storage crate and pick up the storage crate with your USE button, or just pick up the separate bars with your USE button (either way the selling price is the same) and take them to your mining buyer.
Once you get to the buyer, just click your USE button on him and he will buy all your bars of all types all at once.
Now, repeat as often as you like.. your initial investment is done and you should be able to process as much ore as you like. 🙂
Now has been updated to 2021!
Updated to 2022.