One test I found very usefull was showing them various components that they would be using or working with. You could learn a lot by the way they answered or described a component.
For example I would show them a 3/8-16 SHCS and ask them what is was. Possible answers could be, a bolt, a coarse thread bolt, a UNC bolt, allen head bolt, a screw...
Then I would ask the drill size for tapping a hole for the bolt. Possible answers could be 5/16, .312, .3125, depends on percent of thread you want, 7.9mm......
Then I would ask what you use to tighten it. Possible answers could be, a wrench, a allen wrench, a 5/16 hex wrench, a 312 hex wrench.......
Asking them to identify and describe what they would be working with was the best test I ever used. Their answers would tell me not only if they had experience with the component but what type of experience and to what extent.
The people I was interviewing all seemed to like this type of test also. One of the reasons may have been that I would be the one writing down their answers on sheet with the names of each component. I would have a little list of key words I was looking for like 3/8-16, UNC, SHCS, Alloy, Grade 8 and put checks by them. I would also have room to make an extra note if needed.
Not sure if you can use this but it really worked great for me.
Barry1961