A machine tool is only as good as the other equipment used with it, as tooling suppliers often say, but the same is true of workholding. It can take a long time to wind the movable jaw on an old-fashioned vice to clamp a component and sometimes it can work loose, resulting in loss of accuracy or worse.
This was the experience of contract machinist, Dorman Engineering, before owner Roland Dorman bought two Chick One-Lok vices from 1st Machine Tool Accessories earlier this year.
The Loughborough-based subcontractor specialises in component design and reverse engineering as well as producing prototypes, one-offs and small batches of components. Work for the pharmaceutical and electronics industries currently accounts for a large proportion of the subcontractor's business. Producing replacement parts for motorbikes is another specialism, due to Mr Dorman's enthusiasm for them.
A 1,000 x 500 x 500 mm capacity Bridgeport machining centre with part and tool probing and a 58 mm capacity bar-fed CNC lathe with driven tooling from CMZ form the mainstay of the company's machining capability, supported a seat of SolidWorks CAD and SolidCAM software.
Mr Dorman commented, "I previously used two old-style vices but their clamping force and pull-down capability were inadequate. They were also dis-similar, which made it difficult to maintain consistency of positioning when setting up multiple parts for machining on the Bridgeport.
"Components used to tilt upwards by as much as half a degree, which does not sound a lot but is noticeable when working to tolerances as tight as ± 12 microns.
"More seriously, I had a couple of workpieces fly out of the vices when milling with heavy infeed rates, which I need to use in order to maintain production output and profitability."
Mr Dorman reviewed the market to identify optimal replacement vices with four features on the list of essentials: fast action, rigidity, accuracy, and secure pull-down as the vice closes.
He said, "The Chick One-Loks provided all these assets at the lowest price, so were the best value of all the options I looked at.
"They are resistant to vibration under machining loads, resulting in accurate components, increased output and extended tool life as well as less scrap and rework."
Around 25 per cent of the time, when undertaking short production runs, both Chick vices are in the Bridgeport's machining area at the same time, clamping parts for op1 and op2, so a part comes off complete each time the doors open. Occasionally, bigger components are clamped in both vices simultaneously.
Set-ups when changing over to a new job of a different size is faster, as instead of requiring multiple turns of the operating handle, One-Lok features a fast-acting adjustment mechanism. It allows the moveable jaw of the vice to be unlocked and slid quickly to approximately the position it is required along the full 432 mm travel, after which a few turns of the handle secure the part with up to 44.5 kN of clamping force.
The workholding units also provide the reliability needed for extended periods of ghost shift running. On occasion, nearly 24 hours of unattended operation have been achieved, such as when machining a mould that needs a lot of complex surfacing.
Mr Dorman concluded, "The Chick One-Loks from 1st MTA are ideal accessories for a machining centre.
"They provide peace of mind that the workpiece is secure, whilst increasing the accuracy and repeatability of machined parts as well as boosting productivity.
About Dorman Engineering
Roland Dorman originally took a toolmaking apprenticeship through to degree level and holds a BSc Hons in mechanical engineering design. Various jobs followed until his previous post as manufacturing engineer at a firm making special purpose machines for the aerospace industry.
Established at the end of 2009, his company is the only CNC shop within a 10-mile radius of Loughborough that actively promotes the production of single components in virtually any material in turnaround times as fast as 48 hours. It is also frequently involved in helping customers to redesign parts to enable more efficient and cost-effective manufacture.