Drill geometry allows for continuous support


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 from American mechanic Stephen Morse from Massachusetts back in 1863.

While the style and general use of a standard twist drill remains very close to its original roots, there is a constant requirement to 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 into 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 up to 8xD , which is produced under the company’s Dormer product brand.

Including CTW in the range means it is easier to re-grind the drill and offers a more consistent long-term performance. It 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. 
Ricky Payling, Dormer Pramet’s application specialist for rotary tools, explains. He said: “CTW increases both flute volume and cross sectional strength.

“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 increased cutting speeds and greater performance reliability without compromising tool life.”

Re-grinding 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.

Ricky added: “Generally, a drill after re-grind will be at around 75-80 per cent of its original qualities and performance, but with CTW included, this increases significantly to 90-95 per cent.

“Also, for 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.”

Installing CTW into a drill not only enables the complexities of the re-grinding 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 re-grind. This means the drill will not degenerate over time and will maintain its torque strength after repeated re-grinds.

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.

CTW is unique to Dormer Pramet and currently featured in its new R459 drill for applications 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.

For more information about the R459 click here or contact your local Dormer Pramet sales office.