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Woodworth UBL 3 Jaw Chuck with Active Pulldown and Jaw Homing Features

UBL with Jaws

The Woodworth UBL (Universal Ball Lok) is “The Original” ball style, pull down chuck. Developed by Newton Woodworth, it has since been copied worldwide. Where concerns about flatness, parallelism, and perpendicularity exist, a pull down chuck is typically preferred. In order to meet these requirements, a pulldown chuck is utilized, to secure the part against a work stop. The UBL can provide both standard pulldown as well as extended or “active” pulldown, which allows for extended part range. Where roundness is a concern, the UBL utilizes internal jaw homing. This allows the jaws to “compensate” for irregularities associated with unfinished parts such as castings, forgings, etc. This feature is similar to pendulum (or swivel) jaws used on sliding jaw chucks. The advantage the UBL has, is the homing is internal to the chuck. This keeps contaminants associated with the machining process, from affecting the homing mechanism.

The UBL comes in both centralizing and compensating designs, as well as the on/off style, which allows the user to switch between centralizing or compensating. The standard design incorporates either 2 or 3 jaws. However, Forkardt has designed, 1, 4 and 6 jaw designs. The UBL is typically used in first operation turning, but has been incorporated in operations where it is chucking a machined diameter.


  • Standard and Active Pulldown
  • Jaw Homing
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Technical Data
Type / Size UBL160 UBL200 UBL250 UBL300 UBL380 UBL460
O.D. Diameter [mm] 160 200 254.1 298.6 381 457.3
Height [mm] 72.2 84.2 103.2 103.2 116.7 116.7
Actuator Stroke [mm] 11.6 14.3 17.6 17.7 22.3 22.3
Chuck mounting [mm] 104.8 133.4 171.4 171.4 235 330.2
Max. Drawbar Force 2 Jaw [daN] 1700 2600 3100 3550 4400 4400
Max. Static Clamping Force Fsp max. [daN] 4200 6400 7500 8600 10700 10700
Max. Speed RPM [minu02c9¹] 5500 4200 3600 3200 2600 2100
Weight (with jaws) [Kg] 12.41 26.82 41.65 58.2 123.8 152.41
Part No. 2 Jaw Centralizing UBL160010 UBL200010 UBL250010 UBL300010 UBL380010 UBL460010
Part No. 3 Jaw Centralizing UBL160000 UBL200000 UBL250000 UBL300000 UBL380000 UBL460000
Part No. 2 Jaw Compensating UBL160012 UBL200012 UBL250012 UBL300012 UBL380020 UBL460012
Part No. 3 Jaw Compensating UBL160002 UBL200002 UBL250002 UBL300002 UBL380002 UBL460002
All information is subject to change without notice
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