Pullout protection for end mills

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Widia now offers customers the Safe-Lock system by Haimer GmbH, a pull-out protection and adapter system for round-shanked cutting tools that enhances security in heavy duty cutting.

It combines a positive locking feature with on-centre high accuracy for improved process reliability, longer cutting tool life, and higher productivity.

The continuing development of advanced high strength, lightweight materials such as titanium alloys, Inconel, and new aluminium alloys are being investigated by manufacturers in many industries, including aerospace and defense, energy, and transportation. Not only do these new materials present significant machining challenges, competitive pressures in these global industries make finding efficient manufacturing solutions a priority.

“This has become increasingly evident in the last few years, ever since high-performance cutting tools that facilitate this type of machining have been on the market,” says Doug Ewald, lead product manager for Widia tooling systems. “Many industries are upgrading their manufacturing resources (machine tools, cutting tools, and toolholding systems) that can withstand the high torques, feeds and forces to ensure that the operation doesn’t fail and potentially scrap expensive parts.”

The danger of milling cutters being pulled out of the toolholder at these extreme forces has significantly increased. Such toolholders like shrink fit work with friction alone for locking. They have great accuracy, but their clamping force can be insufficient for roughing operations.

The standard industry response for years has been to require Weldon® shanks on cutting tools. The Weldon straight shank with a drive flat for locking in place with a clamping screw was developed to compensate for pullout forces, and to drive the end mill as hard as possible in roughing and other high-metal-removal operations. It is estimated that about 70 per cent of all users use standard Weldon holders for heavy roughing due to security concerns, because the clamping screw creates a positive locking. Tool accuracy and run-out is poor, however, due to characteristic offset and one line contact of the cutting tool in the holder bore. This also contributes to shorter tool life.

Safe-Lock is a pull-out protection system for round-shanked cutting tools. Helical grooves are ground into the shank of the tool. These together with the respective pin drivers in the holder prevent the tool from spinning or being pulled out of the holder altogether under extreme machining conditions. Because the helical path of the grooves means that the length of the tools can be adjusted, tools can be reground and pre-set as usual.

The system can be combined with the latest toolholder systems, such as shrinkfit technology, because it can be used for both high speed as well as heavy chip removal situations. The chuck is heated as usual and the tool inserted with a slightly twisting movement. The locking elements find their own way into the grooves when the tool is turned into the locking position. A spring can be used to aid in the play-free positioning of the tool. The holder cools down after a few seconds, creating the press fit and positive locking.

Concentric accuracy of < 3 μm (0.00012 in.) is achieved during shrinking, a value that is ten times better than any standard clamping in Weldon chucks, claims Widia. The stable and accurate tool clamping achieved in this way allows users to machine even greater cutting depths with higher feed rates. The tangible benefits: time savings, enhanced productivity, lower scrap rates, less vibration, and operator peace of mind.


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