Importance of Center Accuracy

In precision cylindrical grinding/turning operations, we very often come across problems of poor finish and inaccurate geometric forms. Even though the general condition of the machine tools used are in good condition, their bearings, ballscrews and slides contribute to minor deviations. But the main cause of this lack of accuracy is often overlooked: the center holes in the workpiece. It has been proven that the center holes on which the job is supported while being ground, becomes a crucial factor affecting the result drastically in a negative way. Inaccurate centers are bound to produce inaccurate work even made on the best and most expensive grinding machines.

The accuracy of center-type turned-grinded workpieces is heavily dependent upon the accuracy of the workpiece centers. Rough machining or grinding operations in which accuracy is not particularly critical may require only drilled center holes. However, in precision operations, center holes must be ground accurately.

As the production process of workpiece blanks, having center holes on both ends, goes through various processes, such as turning, milling, drilling, rolling, forming, pressing, threading, heat treatment and surface treatment, the workpieces get deformed due to stress, and this affects the form-, position- and the surface quality of the center-holes of the workpieces.

ost cylindrical products, such as shafts, driveshafts and spindles, must be removed from a machine in the middle of the production process and re-attached with their ends reversed. To attain a required shape with the structural limitation of a machine, this reversing step is inevitable in most cases. Therefore, obtaining a most accurate center is crucial to all products with strict tolerance.

Only with a center hole grinder you can obtain the most accurate centers for almost all cylindrical products, such as shafts, spindles, and products requiring cylindrical grinding including taper grinding. If you are committed to providing precision parts, utilization of center hole grinder is a must. 

Surprisingly, many factories that specialize in manufacturing shafts and spindles don’t own a center hole grinder. Even only a few factories use a center hole grinder. It’s an unknown machine tool that can prevent and solve many problems. It is therefore of paramount importance to establish geometrically true and round center holes with accurate alignment as a first step to precision cylindrical grinding.

The main reason many factories who produce axial products don’t own a center grinder is because it is a relatively expensive machine, and a center hole grinder is considered as a less-productive or less-profitably-efficient machine.

Big mistake!! A center hole grinder makes you save a lot of money and o lot of time!

Profimach Centre Hole Grinding Machine

Treatment for Higher Precision

Profimach Centre Hole Grinding Machine are designed and perfected to produce just this, truly circular, geometrically accurate and precisely aligned center holes or center cones in components either in /soft or hardened condition.

Profimach PGCH-180CNC-Series of Center-hole and center-cone grinders not only make poor centers again precise but can move them as required to the optimum position

 – for example, onto the axis of a gear halfway along a shaft bent during hardening.

Some of the benefits;

  • When a subsequent external grinder – cylindrical, gear, spline, thread and its dead centers are in good condition, runout less than 0.001 mm can be obtained on work whose centers have been center ground with our Profimach grinder
  • Subsequent grinding times are DRAMATICALLY reduced.
  • Even case-depth can be assured on important surfaces.
  • Subsequent roundness and concentricity checks have known bases.
  • When center condition is unknown, inspection charts and diagrams are purely speculative.
  • Full and correct contact between work and dead centers prolongs the principle of planetary grinding life of expensive carbide centers.
  • Good center holes reduce drastically the vibrations in next operations