Even though the 3D printer was invented, it would take a while for its technology to catch up with our high precision grinding machines.
The degree of your spirit is what helps you to hone your precision and accuracy, for some reason. Just imagine yourself throwing a ball. You miss the target. Hmm, okay... time to power up like on Dragonball. Up that spirit energy. Turn the degrees up on it. Boom. Awesome. Now throw again. Hit! You hit it! What great precision you have gained by honing your spirit!
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.