Case story - Ring-free machining™ of spool bore holes

The challenge of the rings

Machining spool bore holes in hydraulic valve bodies, hydraulic pumps etc. in cast iron often involves a number of challenges in the machining process.


One of the most common problems is that the bore by the rough pass reamer creates rings that get stuck in the component. The following manual removal of these rings prior to finishing/assembly is a time-consuming and costly process. 


At one of the worlds largest manufacturers of hydraulic valve bodies, Kyocera Unimerco introduced a patented process strategy and technology which eliminates the rings, thus resulting in considerable savings.



The company in question produces 126,000 components of this type per year. The optimisation comprised all machining processes for this particular component focusing on hole quality and process optimization. After in-depth analyses, all tools were replaced by better-performing solutions reducing the total machining time considerably.


Machining cast iron spool bore holes

An example from the total tooling package is the three-pass solution for the spool bore including the following tools:

  • Pilot drill (C7 coated)
  • Core drill (C7 coated)
  • Special finishing reamer


In addition to the C7 coating prolonging the tool life time, tool features include reinforced core diameter and extra guide pads. The result is a straight hole free of rings and excellent hole size consistency achieved at less than half the cycle time.


Optimisation result Before optimisation After optimisation
Total processing time 38.9 sec. 17.3 sec.
Machine costs/component USD 0.97 USD 0.42
Machine costs/year* USD 121,496 USD 53,959

* Hourly factor €67


Considerable savings due to reduced process time

By implementing the optimised tool solution, the company saves 761 hours per year, equaling savings of USD 67,537,-. 


Unequaled savings thanks to RING-FREE MACHINING™ 

However, the above figures do not include the most important results of the optimization efforts. Using the new solution, the chips are pushed out automatically while drilling, and no rings are produced by the rough pass reamer.


Get rid of the rings and cut down the cycle time

Contact us to learn how systematic optimization of production can reduce your unit costs.