Rotating worktable of a vertical lathe, and the jaw boxes that clamp a ring on it
Clamping a large ring on the rotating table of a vertical lathe · independent jaw boxes fitted in the table's T-slots, track and slot widths, clamping force and maximum torque per size, jaw adjustment range, raising the part off the jaw, and measuring the unbalance of workpiece and fixture
One way to hold a large ring on a vertical lathe is with separate jaw boxes bolted into the radial T-slots of the rotating table, each one set in or out to the part. The table's slot width and the spacing of its slots decide which jaw boxes fit; the jaw box decides how much clamping force and stroke each position gives.
Rotating worktables (face plates) of vertical lathes and the jaw boxes and claw clamps mounted in their T-slots. The machine as a whole is covered on the CNC vertical lathe page; rotary tables and indexers for machining centres on the Rotary table page; three-jaw chuck jaws on the Lathe chuck jaw assembly (base jaw and top jaw of a three-jaw chuck) page; vises on the Clamping jaws / vise page; magnetic workholding on the Magnetic chuck page.
CNFX editorial research · Sources checked October 13, 2026 · 5 sources
SCHUNK's SPK jaw boxes are listed as manual lathe chucks for face plates. Each is supplied undrilled; "In case of an order, the gauge and the crossbar are adapted to the relevant face plate", and "For customer-specific adjustment, a table drawing is required". [1]
The three standard SV90° sizes step up in track width, T-slot width, clamping force and maximum torque. Each is delivered with mounting screws, collar nuts, crossbar and eye bolts, "without top jaw, without spanner wrench". [1][2][3]
ERON's 4-claw clamp, listed by the distributor Sumipol, is offered as model KT4 for vertical lathes with 22 mm T-slots and as KT4B for double-column machines with 22, 24 and 28 mm slots. The heading gives a maximum clamping force of 4 kN at 19 N·m tightening torque, while the model table lists 40 kN for both; ask which figure applies before relying on either. [4]
Jaw box
Track width
T-slot
Jaw adjustment range
Max. clamping force
Max. torque
Weight
SPK 180 SV90°
140–180 mm
22–28 mm
75 mm
55 kN
230 Nm
33.5 kg
SPK 220 SV90°
180–220 mm
22–28 mm
90 mm
68 kN
330 Nm
52.7 kg
SPK 260 SV90°
220–260 mm
28–36 mm
100 mm
75 kN
360 Nm
68.8 kg
Send the table drawing (slot width, slot spacing, table diameter) with the enquiry, and state the ring's diameter range, mass and the cutting forces so the number and size of jaw boxes can be chosen.
02
Supporting the part and checking unbalance
Sumipol's page for the ERON clamp instructs, in Thai, that the workpiece must not sit directly on the top face of the claw, and that it is raised on cylinders, blocks or similar; where the 4-claw clamp cannot be fixed to the machine table, a flat clamp or similar is used instead. [4]
Soraluce offers a Table Balancing System (TBS) that "measures the unbalance of the workpiece and fixture on hydrostatic multitasking tables, so that weight on the table can be measured and the unbalance corrected". It says that once balanced, "the system avoids the runout and improves the machining accuracy". [5]
For eccentric or uneven parts, ask the machine builder how unbalance is measured on its table and what limit applies at the planned table speed.
03
Vertical lathe table clamping details
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
Do face plate jaw boxes fit any vertical lathe table?
SCHUNK supplies SPK jaw boxes undrilled and adapts gauge and crossbar to the face plate; a table drawing is needed. [1]
How much clamping force does a jaw box give?
SCHUNK lists 55 kN for SPK 180, 68 kN for SPK 220 and 75 kN for SPK 260. [1][2][3]
Can the ring sit directly on the clamp?
Sumipol's ERON clamp page says no; raise the part on cylinders or blocks. [4]
How can unbalance be measured on the table?
Soraluce's TBS measures workpiece and fixture unbalance on hydrostatic multitasking tables. [5]
Sources and what still needs a direct check
Sources checked 2026-10-13. SCHUNK publishes product pages for its SPK jaw boxes; Sumipol, a Thai distributor, lists the ERON 4-claw clamp; Soraluce describes its Table Balancing System.
