Plastic prototypes, electrodes and injection mould inserts machined faster using quick-acting CNC vices

Machining lead-times at BNL (UK) are much shorter following the purchase of a pair of Chick One-Lok CNC vices through sole UK agent, 1st Machine Tool Accessories. The workholding units have replaced conventional wind-up vices on two Hurco machining centres at the Knaresborough factory in North Yorkshire. Not only are workpieces secured faster, but repeatability and safety are also improved.

BNL’s toolroom supervisor Chris Hargraves said, “With a conventional vice, the movable jaw tends to ride up when a part is clamped, so you have to use a mallet to tap it down. “Then you usually have to tap the handle to make sure the part is fully secured. “We machine up to 50 plastic components at a time here and it was a time-consuming process that is no longer required with the One-Loks.”

He explained that the controlled clamping action produces a pull-down effect as the jaws close, so components are always seated firmly after the handle is tightened by hand. Positioning of the components is also more precise, so machining is more consistent from batch to batch.

Choice of soft or hard jaws

Hard (steel) and soft (aluminium) quick-change Chick jaws with a special machined recess on the reverse are provided through 1st MTA for the Chick One-Lok workholding system. Hard jaws, either plain or stepped, are used when rectangular workpieces are being clamped, such as when machining impressions in tool steel moulds, profiling copper electrodes and milling aluminium fixtures for product assembly. Soft jaws come into their own when round or awkwardly shaped components such as injection moulded plastic parts are being machined.

Soft jaws cannot be used on conventional vices, which presented BNL with a number of problems. If parts were round, only two could be clamped as a third would undoubtedly not be secure. There was also a risk of marking delicate surfaces. Avoiding these drawbacks entailed laborious manufacture of a bespoke fixture or a profiled block that sat low in the vice for holding the parts.

It takes anything up to a minute to wind the handle of a normal vice up to 70 turns if the jaws are wide open and a small part is being clamped. By contrast, a ratchet system on the One-Lok allows the movable jaw to be positioned instantly to within a few millimetres of closure, after which the clamping action is completed with just a few turns of the removable swivel wrench.