Ream on

As Dave Tudor reports, the potential productivity gains possible from the Horn System DR range of insert-based reamers are simply too good to ignore.
Reaming is one of those tried and trusted, traditional processes that has changed very little over the years. By way of contrast, significant advances have been made in cutting tool technology in recent times and as many cutting tool manufacturers – Horn included – will testify, producing ultra efficient tools and inserts has become a highly scientific process as engineers grapple to achieve the optimum balance between cost, productivity and tool life. In many ways the humble reamer has been overlooked. In a holemaking process it's often the final step carried out to provide the required accuracy and surface finish, but reamers – from a design perspective – haven't changed in decades and if a company has a number of reaming operations to carry out, it can be a serious bottleneck in the overall scheme of things. Market suitability The DR range of reamers is produced by Horn under licence from Swiss boring and reaming specialist Urma. Reamers have never been a prominent part of the Horn portfolio so it was probably quite natural for Horn's UK's general manager Mike Green to be a tad sceptical when Horn decided to market the range. “For Horn in Germany, largely because of its strong links with the automotive sector and existing relationship with Urma, it was a logical step,” he explains. “In automotive circles companies dealing with high volume batch work will really be able to benefit from the huge cycle time reductions these tools can provide. Cycle time improvements of 30% are not uncommon when compared to conventional reaming processes and with feed rates up to 7.5m/minute and an effective doubling of tool life, this is taking reaming to a different level. “But in the UK our business is different and my initial question was if high productivity reaming had a place in the somewhat lower quantity, higher complexity batch work that the UK excels in. However, further research and consultation with our own customer base revealed that we do indeed have a number of clients who would really benefit from this revolutionary range of products. Not only that but we believe the DR reamers will enhance and complement our existing portfolio of grooving, milling, broaching, drilling and boring tools perfectly. Introducing this range of new reamers has unearthed a whole new raft of possibilities for us. “I have to say also that the levels of support and training we've had from Urma on the new products has been excellent,” he continues. “Our sales team is looking forward to presenting the new reamers to our customers with a view to significantly enhancing their productivity and output.” Reaming – but not as we know it The DR range of high productivity, high precision insert based modular reamers has been developed for the rapid sizing of blind and through hole diameters from 11.9mm to 100.6mm in steels, castings, non-ferrous materials and plastics. In addition to the reamers themselves, Horn offers a multitude of cutters, inserts, adaptors and alignment aids. Although a standard range is available, Mr Green is keen to emphasise that essentially these are made to order products and totally customisable to suit a customer's application. Delivery leadtimes are currently standing at four to six weeks although Horn would consider carrying stock at Ringwood if order quantities were high enough to justify it. And performance is indeed impressive. Initially the stats look more like a drilling process than reaming. Here's an example: Workpiece: tempered steel 42CrMo4; bore hole diameter 28mm H7; bore hole length 40mm
Reaming insert: HL3H coated carbide.
Machining data: cutting speed (vc) = 180m/minute; speed (n) = 2,046rpm; feed rate per tooth (fZ) = 0.18mm per tooth; number of teeth on reaming insert Z = 8; feed rate per revolution (f) = 1.44mm per revolution; feed rate (f) = 2,946mm/minute.
Primary processing time (Tc): 0.92 seconds/bore including a safety distance of 5mm. Performance aside, the DR reamers simply don't look like traditional reamers! A key feature is the use of a very narrow section high rigidity ring type cutting element, produced using either micrograin carbide (coated and uncoated) or cermet. A noticeable aspect of the inserts' design is the uneven spacing of the cutting teeth which has been found to prevent the onset of vibration and guarantee the required high standard of bore finish and accuracy. New possibilities In its home market, Urma successfully sells the DR range into a number of industry sectors. Automotive applications have already been mentioned but similar successes have been achieved with pump manufacturers, turned parts subcontractors, oil and gas parts and mould and die applications. Mr Green believes that there is similar potential in the UK. “We currently have around six customers that in productivity terms would seriously benefit from a high speed reaming capability,” he says. “Importantly however, I can see this product taking us into brand new markets as well as enhancing existing ones. In the aerospace sector for example high speed reaming could be used very effectively in the manufacture of landing gear assemblies and there are a number of applications in Formula One and motorsport that could also benefit.” On a wider scale, anything that can help UK manufacturers compete on the global stage has got to be good news. This is a product tailor made for high volume manufacturing and this – and products like it – may ultimately make UK companies more competitive against overseas competition. By contrast with more conventional reamer designs, the insert is only 4.3mm thick and although this may seem a little on the thin side testing has shown that most reamer wear occurs within 2mm of the leading edge whilst guidance is normally satisfactory with 4mm total thickness. The thin section also has benefits in terms of reduced friction and chip evacuation, as well as allowing tighter manufacturing tolerances to be maintained. For applications that do require additional guidance the DR system includes holders equipped with guide pads Attachment of the cutting element to the tool holder uses HSK style mating tapers for positioning repeatability within 0.004mm. Ample face to face contact and multiple screw clamping ensure maximum system rigidity and the high repeatability makes for rapid insert exchange. On trial At the moment, Horn is carrying out cutting trials with a select group of customers – including leading UK diesel engine manufacturers. Mr Green recalls: “For one of these the DR system is lined up to replace fine boring which is currently a bottleneck in their manufacturing processes. Previously they were simply unaware that a product like the DR series was available. It's early days yet but preliminary trials have been very successful and things are looking positive for the future. “For another, the potential is equally significant,” he adds. “Two machines on its shopfloor are producing in excess of a million holes every year and every one is reamed.” Depending on the application, different cutting element geometries are available. For through hole applications a left helical fluted cutter is recommended whilst blind hole applications are served by straight fluted cutters. All are available in a wide range of carbide or cermet grades. A comprehensive range of holders and system adaptors is available. Holders for diameters from 11.9mm to 35.6mm come in two different lengths for aspect ratios of 3-4 x and 6-8 x hole diameter. In the case of longer length holders the option of either steel or carbide shank material is available. All are equipped for through tool coolant supply – holders for through hole applications have coolant nozzles immediately behind the cutting element whilst blind hole applications are served by a coolant jet passing through the nose of the cutter/holder assembly. Diameters from 35.601mm to 100.6mm are catered for by a modular shank/insert holder system which offers integrated runout adjustment capability to maximise accuracy. As well as the DR holders, adaptors are available to allow existing proprietary exchangeable head reaming holder systems to use the DR reamer technology, offering a cost-effective upgrade path as most of the performance advantages of DR are maintained. Commensurate with other reports from the industry, Horn is enjoying a marked upturn in business levels and encouragingly has recently taken on two new apprentices. “October has been an excellent month,” he enthuses, “and this has pretty much been the story since the beginning of the year. If we continue in the same vein I predict that we'll be back to 2008 business levels during the first quarter of 2011.” Horn
www.phorn.co.uk