Modern Machine Shop

NOV 2017

Modern Machine Shop is focused on all aspects of metalworking technology - Providing the new product technologies; process solutions; supplier listings; business management; networking; and event information that companies need to be competitive.

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Page 78 of 196

76 MMS November 2017 FEATURE Many of the hand tools Cameron Weiss employs to finish and assemble watches are machined in house by Grant Hughson, his machinist partner. Not all production is in house. Steel watch casings require too much capacity, so they're cut on an L.A.- area shop's turn-mill to a specific finish for handwork. click an area and say, 'pocket this.'" He cites the Geneva striping patterns as a particularly good example of how aesthetics can make outsourcing machining difficult. Visible on the opening photo and on page 77, these broad, diagonal bands stretching across the main plate and bridge derive much of their visual appeal from parallel internal tool marks that arc toward the intersection with an adjacent stripe but never jump the gap. The lines within are shaped a cer- tain way for both visual appeal and to catch dust inside the movement, and maintaining a clear border bet ween each stripe is essential, Mr. Hughson says. Cutting these features on a mill rather than a dedicated Geneva striping machine re quire s w hat h e s ays is a n u nc o nve ntio na l approach to programming. For instance, rather than using a constant stepover on the shop's FANUC Robodrill VMC, he employs a full-width slotting cut, then overlaps half of that cut with another full-width slotting path. From there, no specific measurement or series of me asure me nts can def initively dete r mine whether the striping is correct. It's a purely visual standard, with Mr. Weiss using a microscope to evaluate the machined pattern against a chosen ideal. What's more, width and spacing of the bands can differ slightly from movement to move- ment and from prototype to prototype during the development of a new movement. Certain part features must also be cut from certain portions of the brass square that measures 2 by 2 by 0.125 inches to ensure consistent striping once the movement is assembled. Further complicating things, features spaced too close together don't leave enough space for cutting tools, while those spaced too close to the edge of the stock run up against unsightly tool entry and exit marks. Ensuring tool access to the various main plate and bridge features is also important for chamfer- ing edges to prevent burr formation. Mr. Weiss

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