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Leintelstraße 8, 73262 Reichenbach/Fils

Reverse chamfering of 800 holes under difficult conditions with the special solution “KEMPF RevCut”

Why highly special metal parts from Koblenz are used all over the world becomes clear when you get an insight into the manufacturing processes at Deloro Wear Solutions GmbH. Here, no off-the-shelf series components are developed and manufactured, but complex components are individually developed and manufactured for a wide variety of applications. Quality is an important success factor, which is why Deloro wants to switch to complete machine processing, i.e. “#burr-free from the machine”, even for individual parts and small series. To date, the right tool solutions and strategies have been missing for some deburring operations. The KEMPF company from Reichenbach-Fils in Swabia, as a specialist for such challenges, provided tools such as the “KEMPF TriCut” and the special solution “KEMPF RevCut” for rear bevel processing, with which power plant parts can now be processed reliably.

The company Deloro Wear Solutions GmbH in Koblenz has existed for more than 50 years and has developed over the past decades from a pure foundry to a highly specialized problem solver. Stellite processing is the focus today, as it was back then, and is a truly unique selling point, which is why the range of services has been expanded over time with our own mechanical production and welding shop. This means that further processing of the hardened materials can also be carried out in-house and customers can be offered finished end products or repairs. The specialist for heat- and wear-resistant alloys now employs around 320 people and primarily supplies the food and power plant industries with parts “armored” with stellite, which are used wherever acid, steam or generally high pressures act, resulting in wear problems . Typical components for these areas of application include double wedge slides for pumps, assemblies for screen changers in the plastics recycling sector, and control pistons and valve bushings for hydraulic systems. Since these components are usually used in very large machines, Deloro can process components with a weight of up to four tons and a length of up to 6,000 mm from 10 mm in diameter.

400x drilling & 400x chamfering per component

A small challenge was the production of a steam sieve that would regulate the steam flow in large power plants. The component made of material 1.4901, a highly heat-resistant stainless steel with an outer diameter of 180 mm, a length of 300 mm and a weight of 18 kg, was to be completely machined in a process-safe manner in a batch of just 24 pieces. The problem was the 400 holes with a diameter of 6.3 mm, which were to be provided with a backward counterbore of 120° and a diameter of 10 mm.

Since the counterbore diameter is significantly larger than the bore diameter, standard tools could not be used. A “solution” was needed, which is why Deloro contacted the deburring specialist KEMPF from Reichenbach-Fils. Various processing methods were simulated until it was finally determined which strategy for machine manufacturing the component should be the best.

The standard KEMPF MultiDrill TriCut drill was selected to produce the holes. On the one hand, its 3-cutting edge geometry generates up to 50% more feed compared to conventional drills, and its special sharpening also enables chip breakage, which ensures process reliability Evacuation of chips guaranteed. Drilling applications can therefore be carried out many times faster, more precisely and with a longer tool life.

The MultiDrill TriCut proved to be the first choice for use in this steel alloy with up to 1200 holes, as these performance values ​​far exceeded the tool life and time expected by Deloro, as well as the machining time.

Bohren mit dem MultiDrill TriCut

 Bohrbearbeitung mit dem MultiDrill TriCut


Standard tools did not provide the desired performance

The second step was about chamfering the holes on the inside diameter of the wall. The only standard solution for producing the countersinks was initially a solution with an angle head for machining from the inside. The angle head should have been designed to be narrow, long and stable. However, this would have been difficult to justify economically due to the investment costs.

A reverse countersink from the outside with standard tools was not possible because (due to the bore geometry for the given ratio of cutting diameter and angle to the maximum possible shaft diameter and length) there is no standard tool that works reliably on the market. The tool geometry, which results from the influencing factors, has a very unfavorable effect on the stability of the tool and, due to the resulting vibrations, also on the workpiece surface and ultimately on the service life.

Tests that Deloro carried out in advance with spring-controlled folding tools from a specialized company from neighboring countries in order to circumvent this problem turned out to be not optimal for this application, even if the investment costs were neglected, as they did not work reliably and could not achieve a reasonable service life.


The solution: a simple special tool

Sonderwerkzeug RevCut RückwärtsfaswerkzeugThe KEMPF RevCut, a simple yet ingenious special tool for chamfering the back of the holes, was quickly developed by KEMPF as a special tool.

The idea behind it: to be able to increase the maximum possible strength of the shaft, determined by the hole geometry, by eccentrically plunging it into the hole. For this purpose, the tool was designed with a cutting width that leaves 0.1 mm of “room” on each side when it is inserted into the hole in a spindle-oriented manner. The shaft was designed with a defined clamping surface in the central part to match the orientation of the holder.

After plunging, the tool is moved with the axis of the spindle to the axis of the hole, the spindle is switched on and the lowering process is carried out “normally”. During the first tests it was found that the tool runs very stable and that around 800 holes could be reliably chamfered on the back in material 1.4109.

From an economic point of view, the investment requirement is very low. The carbide cutting edges can be easily replaced and recycled after wear.


Senken mit dem KEMPF RevCut



The Kempf RevCut when lowering the inside. The required processing was only possible thanks to the sophisticated processing strategy.



The “KEMPF ExBurrDrill” drill saves additional chamfering and deburring

Another task was to machine a component made of material 1.7709. A heat-resistant steel that is suitable for temperatures up to 540°C. In total, around 5,000 holes with a diameter of 10 mm had to be made, each with a counterbore of 16 x 90° on the outer diameter.

gratfrei Bohren mit dem KEMPf ExBurrDrillDue to the circumstances, it was decided to use the KEMPF ExBurrDrill.

The main feature of this drill is that the cutting edges create an almost burr-free hole exit. In addition, the “KEMPF ExBurrDrill” was designed for this application as a step drill with a countersink step.

In contrast to the “KEMPF TriCut”, the drilling operation alone takes a little longer, but the entire process is carried out reliably in one operation instead of the three operations of drilling, countersinking and deburring on the back. Setup times for two tools and at least two tool changes are also eliminated.

In this case, you create an advantage in the throughput time of well over 60%, which corresponds to an additional increase in machine capacity to the same extent. The tool's service life was also impressive, as the tool was only replaced after approx. 40,000 mm, which corresponds to approx. 2,000 holes, in order to ensure continuous process reliability. The message was clear: “The drill delivers outstanding results.”



Vorher Nachher Bild


Before and after picture of the steel component:

On the left is the raw part, which is pre-turned from a shaft and then armored with stellite in some areas in the welding shop using the PDA welding process.

After subsequent heat treatment, the component was completely turned on a lathe in two clamping operations and the rear chamfers on the bores were made (right).



Working with special tools creates additional capacity

Based on the positive experiences, Deloro Wear Solutions GmbH will increasingly rely on process-optimized solutions from the deburring specialist KEMPF, as other strategies and tools can save additional clamping, processing time and time-consuming manual work while at the same time optimizing production processes and creating additional capacity.

The quick and uncomplicated implementation of the special tool solution in conjunction with the use of standard tools was the first step.

Das Deloro Team

Kempf Sales Representative Marcus Schneider, machine operator Michael Fössing, CNC-Programmer Andreas Fröhlich, Project responsible for production Andreas Hastrich, Process optimizer Tobias Neisins and machine operator  Georg Hedgar (v.l..n.r.)


View KEMPF RevCut in our Onlineshop »