ERA Concealed Security Bolt
Good corrosion resistance
Readily joined cold riveting
Productivity increase of 300%
Courtesy of J E Reynolds & Co Ltd
Notes:
ERA Security Products Concealed Security Bolt
J E Reynolds & Co Ltd of Short Heath Willenhall West Midlands are well known manufacturers of quality security products marketed under the ERA brand name. Products, many of which conform to relevant British Standards and are frequently Which Magazine Best Buys include Mortice, Rim and Window Locks and Security Bolts. The company are continually striving for improved product performance without increased manufacturing costs. This was achieved recently by replacing the welded tubular steel housing of their concealed security bolts with brass.
A concealed security bolt is simply a round sliding bolt housed in a tube, the bolt is driven backwards and forwards by a splined key inserted in the tube which mates with a rack on it. The assembly is fitted into the edge of a door or window and is intended to replace or supplement existing locks and handles.
The original design called for a steel tube fixed to a end plate by firstly peening over the tube and brazing. The tube was machined and then finally painted. A number of problems were discovered, firstly the tube and end plate assembly had to go off site for brazing, this disrupted the flow within the manufacturing cell which had been set up for the product. Secondly the machining required a drilling operation on the tube and the break out of the drill was never clean leaving a "flap" on the bore. A number of techniques were tried to remove this but the usual effect was to force the flap back into the hole.
Consideration was given to replacing the steel tube with brass to overcome the manufacturing problems but brass tube was five times the price of the steel. Would it be cost effective? Trials confirmed the greater degree of formability of brass allowing the painted end plate to be secured without the need for brazing. Secondly the brass machined quicker which was expected, but an additional bonus was a clean break through on drilling, enabling all internal machining burrs to be simply removed by the reaming operation required to finally size the bore. External burrs on the key entry holes are removed by counter sinking which also provides a natural lead in for the key.
The above benefits meant the product lent itself to effective cell manufacture eliminating buffer stocks of assemblies which were being brazed off site. Production rates increased by over 300% (130 to 450 completed assemblies an hour) paying for the increased price of brass tube.