A horizontal mill has the same sort but the cutters are mounted on a horizontal spindle (see Arbor milling)
across the table. Many horizontal mills also feature a built-in rotary
table that allows milling at various angles; this feature is called a universal table.
While endmills and the other types of tools available to a vertical
mill may be used in a horizontal mill, their real advantage lies in
arbor-mounted cutters, called side and face mills, which have a cross
section rather like a circular saw, but are generally wider and smaller
in diameter. Because the cutters have good support from the arbor and
have a larger cross-sectional area than an end mill, quite heavy cuts
can be taken enabling rapid material removal rates. These are used to
mill grooves and slots. Plain mills are used to shape flat surfaces.
Several cutters may be ganged together on the arbor to mill a complex
shape of slots and planes. Special cutters can also cut grooves, bevels,
radii, or indeed any section desired. These specialty cutters tend to
be expensive. Simplex mills have one spindle, and duplex mills have two.
It is also easier to cut gears
on a horizontal mill. Some horizontal milling machines are equipped
with a power-take-off provision on the table. This allows the table feed
to be synchronized to a rotary fixture, enabling the milling of spiral
features such as hypoid gears.