What is "Morag Charutz"?
Rashi: It is a heavy wooden Kli. It has many grooves, like a smith's iron file. They drag it on straw of sheaves, until it become fines stubble.
Radak #1: They are Morag and Charutz; the prefix Vov is omitted, like "Shemesh Yare'ach" (Chabakuk 3:11). Even though the Morag is the Charutz, there are two aspects to the Kli. One is called Morag, and the other Charutz. When you left Galus, I made you to the Resha'im like a new Morag v'Charutz.
Radak #2: Charutz is an adjective describing Morag; it cuts well. Charutz refers to cutting - "Charutzim Yamav" (Iyov 14:5).
Why does it say "Chadash"?
Rashi: This is before the faces of the ridges were smoothed; it cuts greatly. When it is old, the faces of the ridges are smoothed.
Malbim: The Nochrim are depicted as chaff that is removed via a new Charutz. I.e. this will not come via old merit, for they already consumed it, rather, via new merit.
What is "Ba'al Pipiyos"?
Rashi: They are the blades of the ridges.
Radak: It has many blades. This is why the Pei and Yud were doubled. Every Morag has blades; they remove the shell from the grain.
Malbim: [Yisrael will have] many powers via many Mitzvos.
Why does it mention mountains and hills?
Radak: They are a metaphor for the kings of the seven Kena'ani nations and their officers.
Malbim: Great mountains depict that the wheat that is cut fine. Hills depict the chaff. These are a metaphor for the officers and servants - they will be cut fine and eradicated via the Charutz, i.e. Yisrael.
