Tool extensions

Most companies utilizing CNC routers have encountered an application where extended tool length is required, to reach into a deep profile or achieve a smaller radius in a specific area of the part. After running a program simulation, it becomes apparent the splindle housing or tool holder will hit the material before the cutting tool. There is generally a process of seeking out longer tooling, which is often very expensive and susceptible to breakage. In many cases, long tooling is impossible to acquire, which generally leads to a search for a tool extension. Although tool extenders can be purchased with a ER collet system, and easily assembled with the cutting tool to solve an application challenge, there are several concerns which must be considered, and some new technology which provides safer and more accurate performance. The emergence of 5 axis machinery does allow more flexibility in some situations, but often 
the extension of the tool 
and holder is the only option.
Image 1A – shows an extreme example of an application which requires tool extension. In this scenario, the part requires 3/8 pocket holes to be drilled on a 15-degree angle on a 5 axis CNC. A standard 7-inch-long drill will not work because the spindle housing will hit the material or the large collet nut will collide with material, before hole can be drilled to cull depth.

Problematic Solution
For many years, it has been common to use tool extenders with tiny ER mechanical collets, but the most common solution is NOT always the best solution!  
Image 1B – shows a poor solution involving two collets holding in sequence from machine spindle to cutting tool. This system will work in some cases, but the combined runout and inaccuracy of two collets can be a serious issue. Standard ER collets have inherent problems with accuracy and clamping force, and 
the smaller ER collet versions are even more problematic, as they stretch and wear much easier. Many tool extenders use ER 16 collets, which will not hold up to the 
force exerted by long tools, 
resulting in tool runout and excessive tool deflection. Extreme tool deflection is not only bad for tool performance, but it can also be unsafe in extreme circumstances.

Best Solution
ETP Sweden has been making hydraulic tool holders for many years, and has some new technology which is available through most tooling suppliers in North America.  
Image 2 – shows the absolute best option for holding tools in an extending reach scenario. ETP Sweden has designed these holders for specific drilling and routing applications at low feed rates. Hydro clamping holder technology has been in existence for many years, but this slim pencil version is the 1st of it’s kind. It is designed to eliminate run out and drastically increase clamping force compared to ER collets. Hydraulic tool holding systems have a proven record of improving cut quality and optimizing tool performance on CNC machines, but this system has an added safety benefit. By clamping tools hydraulically on one end of the holder, we can effectively eliminate one point of run out, and the opposite end of the holder is built directly into the HSK holder, which eliminates another connection point. The result is an extended tool system which can perform the same long reach applications, with far greater accuracy and safety compared to ER mechanical collets.   

Important Considerations
It is very important to respect the fact that extended reach applications are sometimes impossible. If attempting to use tool extensions to achieve longer reach, great care and consideration of machine parameters, depth of cut, material density, part holding and a host of other machine variables must be considered. It is recommended to consult with your tooling supplier, to determine the best and safest course of action. If machine feed rates are run very slow, and parts are held properly on a rigid machine, it is possible to cut most materials successfully with a hydraulic pencil holder.
As the industry demands more complex parts and material continues to evolve, it is critical to have a safe effective solution for extended length routing applications. Hydraulic pencil holders do provide the highest level of rigidity and accuracy when machining at extended lengths. If properly set up, and consideration of all the variables are made, this holding system can provide a competitive advantage when quoting difficult CNC machining applications.