Lathe speed and workpiece diameter: the speed charts in the makers' manuals

Why the speed depends on the diameter

Powermatic's 3520C manual prints a table of recommended lathe speeds per diameter of workpiece, with separate columns for roughing, general cutting and finishing.

RIKON's 70-1516VSR manual recommends low speeds for roughing stock and for long or large-diameter workpieces, and refers the reader to its speed chart for recommended speeds based on the diameter of the workpiece. (RIKON Power Tools)

Taikra doesn't rank or test tools; every figure here is from the maker's own manual or page, linked. The chart in each lathe's manual is the reference for that lathe.

The speed chart in the Powermatic 3520C manual

For work under 2" in diameter, the chart lists 1520 RPM for roughing and 3000 RPM for both general cutting and finishing. (Powermatic)

Work 2" to 4" is listed at 760, 1600 and 2290 RPM, and work 6" to 8" at 380, 810 and 1125 RPM. (Powermatic)

For 10" to 12" the chart lists 255 RPM roughing, 540 general cutting and 750 finishing. (Powermatic)

At the large end, work 16" to 20" is listed at 175, 325 and 450 RPM, and work 20" to 24" at 175, 260 and 375 RPM. (Powermatic)

In every row of the chart, the roughing figure is lower than the general-cutting and finishing figures.

Speed ranges, belts and pulleys

Powermatic lists the 3520C's spindle speeds as 15-1200 RPM in its low range and 40-3200 RPM in its high range.

RIKON's 70-1516VSR has three speed ranges, 250-850, 430-1450 and 950-3200 RPM. (RIKON Power Tools)

RIKON's 70-305 manual describes its two ranges by purpose: one for speed (0-3200) and one for torque (0-1200). (RIKON Power Tools)

The larger RIKON 70-3040 lists variable speeds of 20 - 3,850 RPM across three ranges: 20 - 650, 50 - 1,750 and 100 - 3,850 RPM. (RIKON Power Tools)

WEN explains that a fixed-speed lathe cannot run at any speed between its set speeds: the drive belt runs on pulleys of various radii, and changing the belt's position changes the spindle's speed. (WEN Products)

RIKON's 70-100 is a step-pulley lathe of that kind, with six speeds: 430, 810, 1230, 1810, 2670 and 3900 RPM. (RIKON Power Tools)

WEN's mini 3421 lathe is variable from 750 to 3200 RPM. (WEN Products)

Starting, sanding and parting speeds in the manuals

Powermatic's 3520C manual and WEN's 3421 manual both say to select the speed for the job, start at a low speed and let the lathe ramp up to operating speed. (WEN Products)

For sanding and finishing, the 3520C manual says to set the lathe to approximately 500 RPM, because high speed can build friction while sanding and cause heat check in some woods. (Powermatic)

RIKON's 70-1516VSR manual also says to use low speeds when sanding or applying finishes, to avoid heat build-up. (RIKON Power Tools)

For parting through a workpiece, the 3520C manual says to turn the lathe down to a lower RPM. (Powermatic)

For what swing and distance between centers mean, see lathe swing and distance between centers. Every lathe in the catalogue, with its listed speed range, is on the lathes page, including the Powermatic 3520C.