Machining Fundamentals

I thought this would be a great place to do a quick talk on Tool Offset.  Tool Offset is the amount you must “Offsetâ€� the tool while machining.  For example, the tool paths that we created in CAM are located in the dead center of the tool unless you do something about it. Most times you set the tool offset in your CAM program, but sometimes you might have to do it during the machining phase, depending on your machine. 
What if you had a one-inch diameter tool, we will use an end mill in this example, and you needed to take off .25â€� around the perimeter of a 5â€� by 5â€� block of aluminum?  Without tool offset, the tool path would be around the perimeter of the block.  The end mill would take off half of its diameter or .5â€� inches.  You need to offset the tool so this does not happen.  In this case you would offset the tool outside of the block by .25â€�, then the end mill would take off .25â€� of material.
Zeroing the machine out
When beginning your machining, you always need to zero out the machine.  You need to let the control software know that this is going to be the starting point for the whole project.  When “Zeroingâ€� out the machine, a lot of the time you will use an edge finder when milling.  Most times in plasma cutting, you will just pick your starting point on the steel and begin the program there.
The final “Part�
Parts are the outcome of your work.  That is unless you are making artistic pieces.  Parts need to be made to specification.  Most often machinists will check their parts as they come out of the CNC Machine they are running.  Many times, they will use a go/no-go gauge.  With a go/no-go gauge they can quickly check out the critical dimension of the part and reload the machine.
Chips?
Machinist call the material being removed “Chips.â€�  This is because most things that are machined are metal and they come off the part in chip form.  Chips can be very sharp and dangerous.  You have to be very aware of where they are flying as they are being removed.  Quite a few machines will have enclosures around them to block these chips from flying around.
Ivan is active in CNC Machining and G Code. Compucarve is one of his expertise.