The Horn System DR range of insert based modular reamers are produced, by Horn Cutting Tools under license from the Swiss based boring and reaming specialist Urma AG, for rapid sizing of blind and through hole diameters, from 11.9 mm to 100.6 mm.

System DR has been developed for use with steels, castings, non-ferrous materials and plastics. An example of System DR performance is outlined below:-

Workpiece:
– tempered steel 42CrMo4, No.1.7225, tensile strength Rm ~800 N/mm²
– bore hole diameter 28 H7
– bore hole length 40 mm

Reaming insert:
– HL3H coated carbide

Machining data:
– cutting speed vc = 180 m/min.
– speed n = 2,046 rpm
– feed rate per tooth fZ = 0.18 mm per tooth
– number of teeth of the reaming insert Z = 8
– feed rate per revolution f = 1.44 mm per revolution
– feed rate f = 2,946 mm/min

Primary processing time:
– Tc = 0.92 s/bore hole including safety distance 5 mm

A key feature of DR reamers 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; this has been found to prevent the onset of vibration and guarantees the required high standard of bore finish and accuracy.

Attachment of the cutting element to the tool holder uses HSK-style mating tapers for positioning repeatability within 0.004 mm.

Holders for diameters from 11.9 mm to 35.6 mm are available 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.

Diameters from 35.601 mm to 100.6 mm are catered for by a modular shank/insert holder system which offers integrated run-out adjustment capability to maximize 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. This offers a cost-effective upgrade path as most of the performance advantages of DR are maintained.