Dormer Pramet Drill geometry allows for continuous support

Editor: Barbara Schulz

Continuously Thinned Web (CTW) technology is unique to Dormer Pramet’s rotary drilling range and provides customers with a variety of benefits to support the life of the cutting tool, Ricky Payling, Dormer Pramet’s application specialist for rotary tools, explains.

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Dormer Pramet’s new R459 solid carbide drill 8xD.
Dormer Pramet’s new R459 solid carbide drill 8xD.
(Source: Dormer Pramet)

The traditional ‘Twist Drill’ has been around for more than 150 years and its overall design has changed very little during this time. This is recognition, if it was ever needed, of the innovative invention of American mechanic Stephen Morse from Massachusetts back in 1863. However, there will always remain the ambition to improve on perfection!

Constant requirement to push boundaries

Constant requirement to push boundaries

While the style and general use of a standard twist drill remains very close to its original roots, there is a constant requirement to push the boundaries and find new ways to enhance performance, extend tool life and reduce overall costs.


Dormer Pramet’s philosophy has always been to provide customers with simple and reliable solutions to support and resolve their manufacturing challenges in an efficient and cost-effective manner. This ethos was a key element in their development of a distinctive feature for the working end of the traditional drill.

Continuously Thinned Web (CTW) technology is unique to Dormer Pramet’s rotary drilling range and provides customers with a variety of benefits to support the life of the cutting tool, without compromising performance. CTW geometry is a key feature of the newly released R459 multi-material drill for applications of up to 8xD, which is produced under the company’s Dormer product brand. Including CTW in the range means it is easier to regrind the drill and offers more consistent long-term performance. This will ensure the drill is restored to as close to its original properties as possible after regrinding, providing a cost-effective solution in a simplified manner.

Traditionally, web thinning is performed as an additional operation after point grinding. A drill point is thinned by shortening the length of the chisel edge to reduce the thrust force needed when drilling. CTW technology simplifies the chisel-thinning process as the depth is already set and therefore no adjustments are needed during regrind, regardless of drill length.

“CTW increases both flute volume and cross-sectional strength," Ricky Payling, Dormer Pramet’s application specialist for rotary tools, explains. “The combination of these elements ensures consistent forces throughout the drilling cycle, with little or no increase in power requirement as the drill penetrates deeper into the hole. This, in turn, allows for increased cutting speeds and greater performance reliability without compromising tool life.”

CTW reduces time needed for regrinding

CTW reduces time needed for regrinding

Regrinding a drill can be a cost-effective solution for an end-user to extend the life of a cutting tool, but it can be a complex procedure and needs to be performed accurately to ensure the product achieves a consistently good level of performance. “Generally, a drill after re-grind will be at around 75-80% of its original qualities and performance, but with CTW included, this increases significantly to 90-95%,” Payling says. “Also, a regrind company working with a batch of drills with CTW included will significantly reduce its lead time, compared with those that do not. This offers a quick turn-around for customers, simplified logistics, and machine downtime is kept to a minimum.”

A showcase for the international tool & mould industry

Installing CTW into a drill not only enables the complexities of the regrinding operation to be reduced but because an amount of the web thinning is built into the design, the symmetry of the tool is retained after regrind. This means the drill will not degenerate over time and will maintain its torque strength after repeated regrinds. By integrating part of the web-thinning feature within the flute form, the design is effectively thinned throughout the life of the drill, without passing on the costs and difficulties associated with this additional operation to the user. Also, as thrust forces are kept consistently low, the result is less wear and tear on the machine tool, providing another time and cost-saving benefit for the end-user.

In-house testing

CTW is unique to Dormer Pramet and currently featured in its new R459 drill for applications of up to 8xD in a wide range of materials. However, the cutting tool company hopes to expand its use to other drilling ranges in the near future. A key feature of the R459 is its versatility in machining a variety of materials. Recent in-house testing conducted by Dormer Pramet using the new drill on aluminium, hardened steel and stainless steel showcased how CTW could withstand differing applications and conditions.

During a test in stainless steel 316L with cutting data of Vc 35 m/min at a feed of 0.1 mm/rev (1,395 rpm at 140 mm/min), the R459 ran for 30 minutes of contact time and showed a small amount of pick-up, with a nice even wear scar across the cutting edges.Similarly, when machining aluminium, the drill was run at Dormer catalogue data Vc 285 m/min (11,340 rpm) at a feed of 0.26 mm/rev (2,950 mm/min). After 30 minutes of contact time, the drill showed minimal wear across cutting edges, with a small amount of pick-up.

Staying in the fast lane in Europe

In the development of the R459 with CTW, Dormer Pramet performed a range of competitor tests, where the drill continued to perform well against five others.

To ensure fairness against the competition, all the drills were tested in the same conditions. With hole depth set at 40 mm while machining hardened steel (AMG 1.5), speed was 80 m/min at 5,092 rpm, with 0.09 mm/rev feed at 458 mm/min. From those tested, Dormer’s drill and only one other competitor lasted the full 30 minutes, drilling more than 340 holes without any problems. In the same timeframe, another lasted half an hour but offered a poor finish and noisy performance.

From the initial test, the best performing competitor was then selected to compare tool life using the same conditions. The R459 lasted for a further 80 minutes, drilling 900 holes without any problems, while the competitor was badly worn after completing the same operation. The tests showcased that even with the CTW web-thinning feature included, deep-hole drills can perform successfully in a range of material applications. This consistent performance and ultimately a reduction in costs offers a win-win solution.