Small diameter tube drilled and tapped accurately

An unusual job involved drilling and tapping fine holes in silver-plated, mild steel tube requiring holes to be produced within tight positioning tolerances.

An unusual job completed in January 2004 by Holifields, a subcontractor in Abingdon, UK, involved drilling and tapping fine holes in silver-plated, mild steel tube.

Two such components were machined for use in an innovative sound curtain being developed by a London company, Aylo, to halve the level of environmental noise entering a room, or even to convert it to a soothing sound that resembles the sea.

The tubes, covered in a plastic sleeve to protect the silver surface, were machined on one of Holifields' 12-station Miyano turret mills equipped with an indexing head and an opposed tailstock.

Critical was the +/-0.1 mm positional tolerance from the end of the tube to the centres of three 3 mm diameter holes unequally spaced at up to about halfway along the component.

They were drilled through the 0.75mm wall on one side only and each was threaded with an M3 tap.

The 184 mm long, 10mm OD tube was then indexed through 90 degrees for a 2mm diameter hole to be drilled, again through one side of the tube only.

Andreas Raptopoulos, inventor of the sound curtain, commented, "In addition to the tube drilling job, Holifields has completed other machining tasks for us including various parts in acrylic, and we have been very happy with the service.

The subcontractor regularly carries out work for the instrumentation and scientific sectors and has recently won business from a number of college departments producing prototype and experimental products.

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