采用顺铣，必须要求铣床工作台进给丝杠螺母副有消除侧向间隙机构，或采取其它有效措施。

     By the third year of teaching I'd begun to expect Christmas break more for the school holiday
and less for the excitement of the children. I was teaching fourth grade and my students had made
me__1__. I just had to get through one of the hardest days of the school year.
     The morning bell rang. I walked__2__through the cold into the overly heated school building.
Twentytwo smiling faces__3__me at the school bus stop. I forced myself to __4__ their smiles.
Back into the classroom, they__5__, comparing plans for the__6__. I had to remove one student
from each arm__7__I could take a seat at my desk for my morning duties. Before I could find my
roll book(点名册) my desk was covered with__8__and gifts followed by a__9__of "Merry
Christmas" wishes.
     "Oh, thank you," I must have__10__a million times. Each gift was truly special to me, except
my__11__mood(情绪). It was kind of them to__12__me. After a while, I heard a small nervous
__13__say my name. I looked up to see Brandon standing__14__by my desk, holding a small,
round gift. "This is for you."
"Thank you, Sweetheart." I laid it on my desk with the others."Um, could you__15__it now?"
     I gently tore at the paper and tape. "__16__," he said, "it's breakable." Slowly I opened a small,
green Christmas tree ornament(装饰物), complete with a hook already__17__. It dawned on me
what he had done. Then a nearby student said that he just pulled that off his own tree. I tried to keep
my__18__back.
     Later that day, I sat__19__the ornament in my hands. Was I really so important to this child that
he had searched for something to give me? Now every year as I__20__pull a green Christmas ball
from my ornament box, I remember the deep influence my students have on me.