Having been on both the hiring and hiree end of CNC machining I can say that I see 2 initial paths to take when hiring a CNC machinist.1) Hire someone you know who has the abilities necessary 2) Interview the individuals considered for hire taking into account your unique situation.
First, ask yourself what kind of employee you need. Obviously, timeliness, appearance, organization skills, and other seemingly "expected" employee traits cannot completely be known until you hire the person; you can usually rely on references, and of course "gut feeling" as to whether an employee will be able to meet these basic criteria. But what you really need to know is can the person fulfill your expectations for their position.
Do you need an operator to set-up EIA machines from existing programs or programs that someone else has written? If so, they will need to be familiar with setting up the machine to run.
Of course, as was mentioned in another post, there are talented employees out there that have never set-up your exact machine before but can draw upon their knowledge of the machines they have set-up to learn quickly. My first "G-code" machine to fool with was a Haas VF-3. After changing jobs I was easily able to assimilate (in the matter of hours)the set-up of a Mazatrol EIA(Yasnac MX-3) machine because of certain constants from machine tool to machine tool. Where are tool length and diameter offsets stored? How does one get the machine to record those offsets. What are the procedures for power-up? etc...
Do you need someone to do the whole cookie? Hand them a print and a job order and not see them again 'til they've completed the job and are looking for another job order? This is where there are two close yet separate paths to look at. Are your machines conversational? Hurcos, Mazaks, et.al. are great machines because a proficient operator will be able to do the entire setup at the machine, including programming. Are you running "G-code" machines? The machinist will have to be familiar with CAM programming, computers in general, and some sort of CAD program in addition to setting up of the machine.
Proficiency in math is more of a bonus than anything. I use trig almost everyday and can't see how anyone could get by without it, but not too many people would be able to say, figure out how to find the locations of milling a hex or the tangency points between a straight line and a partial radius. Ask the machinist what tools he uses most. Aside from the obvious answer--my head-- I think a good calculator should be in the list as well. When I was doing a little moonlighting, I tried to figure out what tools I needed to bring from my dayjob. At first I brought most everything; prepared for just about anything. I soon settled into bringing the tools I used most; 12in. Calipers, TI-35 calculator, Metric & Standard Allen wrences, notepad, and pencils/pens.
Resumes are a prospective employees' means of showing off their supposed abilities. They are necessary, but I am loathe to compare people from their resumes only. I consider myself a good machinist and employee and my resume doesn't look nearly as great as some that I've received. Maybe I just have a problem putting together resumes and others have a better knack for it. Nothing beats meeting with the employee face to face. As a general rule, most companies do not put their names in classified ads, some include only a fax number, some go a little extra and include their address. History has shown that I've hired from the resourceful individuals that figured out where we were and came in to talk about the position and hand in their resumes themselves. I can use the internet to tell me the name and address of the fax number that I see in a classified ad, but the fact that that company did not include any other information is indicative of their probable aversion to having people show up to talk to them, so I don't do that; I figure it's their loss. So leave a "clue" in the ad as to where you are, and a few resourceful people (usually the people you want to hire) will show up. I've been busy before when these people dropped in, so we didn't get a chance to talk right then, but I definitely scheduled an appointment to interview them. Another idea we've been kicking around is posting job openings on the internet only. That way,we think, we will see fewer applications, but will probably see a "higher quality" of employee applying for the position. Obviously someone who knows how to use a computer, and is a little more "upper echelon". We haven't tried it yet, but if you do, and it works, pass the info along. Hope this helps.