In horizontal milling process (up/down) milling provides better surface finish and (up/down) milling provide longer tool life.

• A. Up milling process provide better surface finish because it start cutting process with unfinished surface & in down milling longer tool life because of relative velocity between chip & tool so lower temperature hence less diffusion.
• B. Down milling process provide better surface finish because it start cutting process with unfinished surface & in down milling longer tool life because of relative velocity between chip & tool so lower temperature hence less diffusion.
• C. Down milling process provide better surface finish because it start cutting process with unfinished surface & in down milling longer tool life because of relative velocity between chip & tool so higher temperature hence less diffusion.
• D. Down milling process provide better surface finish because it start cutting process with finished surface & in down milling longer tool life because of relative velocity between chip & tool so lower temperature hence less diffusion.