Rotating centers for lathes

This article will focus on turning centers, their design, varieties and features of operation.

One of the most common workpieces processed on lathes are shafts, and shafts of different lengths. In order to achieve the necessary surface quality, they need to be fixed quite rigidly and securely. This is done in the most effective and proven way - on the one hand, the shaft is clamped in cartridge, and on the other hand it is compressed center. In most cases, a rotating center is used for this, which is installed in the pinole of the tailstock.

In which cases it is necessary to use a rotating center:

• The length of the workpiece is 5 times the diameter. 

• Turning heavy parts at high speeds (high RPM and feed). 

• Large thickness of the removed chips. 

• When the finishing will take place on the grinding machine. 

Advantages of using the centers:

• Long service life. 

• Resistance to high loads. 

• The ability to increase the processing speed. 

• Improving the performance of equipment. 

• Versatility — can be used on manually operated machines and on CNC equipment. 

• High quality parts.
  

Design of rotating centers

The rotating center consists of a conical tip, a shaft and a bearing housed in a steel housing. It largely depends on the bearing on which modes the center can operate, as well as it reduces friction.

In standard operating modes, a center with a tip angle of 60 ° is used, in severe modes it is advisable to use an angle of 90 °.

Varieties

Depending on the specifics of the tasks being solved when turning the center, there are several types:

• Thrust center — used at low processing speeds. It is necessary to make a centering hole beforehand. 

• Thrust with a cut cone — used when cutting the end

• Rotating — used at high processing speeds, where the thrust can no longer be applied.

• Fungal — has a tip with a truncated cone. It is used for fixing parts with an internal hole (pipes, hollow shafts). 

  

• With a rotating nut — for easy removal from the tailstock

  

• With replaceable tips — the ability to process a wide range of parts using just one center

The centers for lathes are made of high-strength alloy steel. Depending on the complexity of the process, they can be ordinary and reinforced. The latter are used when working with heavy products. Reinforced is characterized by strength and resistance to high loads.

 

Specifics of operation

Before starting work, the turner must take into account the runout errors. It occurs due to wear of the bearings or the tip, insufficiently rigid fixation. If the requirements do not allow such an error, it is better to use other equipment.

What nuances should be taken into account when processing in the centers:

• The axes of the spindle and the center must coincide, otherwise there will be errors in processing. When turning parts with a high accuracy class, it is necessary to leave allowances for finishing. 

• The clamping force should securely fix the workpiece, but at the same time not interfere with its rotation.

• When working at high speeds, it is necessary to use lubricant to reduce the wear of the tip. 

Important!

The beating of the rotating center leads to a radial beating of the part relative to the axis. Further processing of the same workpiece on another machine may lead to a misalignment.

If a strong beating is detected, the conical tip must be sanded with a special tool that is attached to the tool holder. After checking the template, in case of a satisfactory result, you can start metalworking.

Important!

When turning at high speeds, the center tip wears out and the centering hole breaks. To extend the life of the tooling, the tip is treated with a protective lubricant.

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Sources:

1) Bison-Bial 2015 catalog

2) https://vseostankah.com/tokarnye-stanki/vrashhayushhijsya-tsentr-nepodvizhnyj-gribkovyj.html

3) https://mekkain.ru/library/czentr-upornyij.html

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