Originally Posted by
Archibald
I got a lot of emails asking about the answers to the test, so here they are...
1. The lid for a box is 30” X 36”. The side boards are made of standard 1” pine dimensional lumber. What lengths should the side boards be?
Not really a trick question, but dimensional lumber means finished dimension. So a 1-by board is really only .75" thick. That makes one side full length and the other 1.5" shorter. Correct answers would be either 30x34.5 or 28.5x36. Surprisingly few folks got this right.
2. Put in order from smallest to largest: Letter F drill bit, 1/8”, 3mm, #7 drill bit, one hundred and thirteen thousandths, 10mm end mill, tap drill for 3/8-16 fastener, .250", 10 gauge steel plate.
Decimal equivalents are in parenthesis.
One hundred & thirteen thousandths (.113")
3mm (.118")
1/8" (.125")
10-gauge steel plate (.135" and the steel declaration was important)
#7 drill bit (.210").
.250", Letter F drill bit (.257")
Tap drill for 3/8-16 fastener (a few answers for this, but generally .3125" diameter for cutting taps, .348" for forming taps)
10mm end mill (.394")
3. How many 8” pieces can you cut out of a 12’ long piece of material? Think about it, yo.
Less than 18 is the correct answer. You always lose the kerf or thickness of the cut.
4. If two sides of a right triangle are 3 and 4 feet long. How long is the hypotenuse?
The Pythagorean Theorem, A2+ B2= C2. Answer is 5.
5. If a 2” ID tube is slit open with a ˝” cutter, how long is the piece if spread out flat?
ID = Inner Diameter so you have to find the inner circumference, so 2 x pi. Lots of folks got this right, but missed the fact that the 1/2" wide cut is through a circular segment. Correct answer would be 5.778". Nobody got this completely right.
6. How many thousandths are in an inch?
1,000
7. What does "five-tenths" mean to you?
In a machine shop, "tenths" mean 1/10,000". So five-tenths means .0005" or 5/10,000ths.
8. All other variables being equal what is the difference in length of a chainstay for a 24” inch wheel and a 29” wheel?
2.5"
9. Name 20 bicycle frame brands.
Any 20 would do but we were really looking to see mostly handmade brands.
10. What is the g-code for a rapid move?
G0 or G00 are both correct.
11. What does "mcx" mean to you?
Mastercam X (and X+) file designator. Knowing this would show at least a familiarity with Mastercam.
12. If the guy who signs your paycheck says he wants something done right away, how long should you wait before doing it?
Lots of great answers to this!
13. What is the difference between precision and accuracy?
In a machine shop, accuracy is how close you are to your target dimension, precision is your repeatability. You can have great precision and poor accuracy, but you can't have great accuracy without also having great precision.
14. What does SFM mean to you?
"Surface Feet per Minute" was the answer we were looking for.
15. Use the word "interpolate" in a sentence.
We were looking for a machine shop perspective, for example, "Circular interpolation is used to translate linear positions into arcs or circular motions." Other answers along these lines were also acceptable.
16. You walk into a machine shop and you find that none of the calculators work as you might expect them to. Why is that?
We had exactly one person get this right and Elroy says it was because he was old. The answer is RPN or Reverse Polish Notation. For some reason, all my RPN calculators keep getting broken.
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