Machining center toolholder knowledge

March 03, 2021

Nowadays, CNC machining center has been widely used in factories. Different models, standards and parts of CNC machining center are more and more well known. The toolholder is the joint between the machine tool and the cutting tool. The toolholder is a key link affecting the concentricity and dynamic balance.

The common unit of toolholder is taper

Most of the handles we see everyday are 7:24. This is a sk universal toolholder with a taper of 7:24. The other is HSK vacuum toolholder with taper of 1:10.

Concentricity can determine whether the cutting amount of each cutting edge is uniform when the tool rotates for one circle, and the dynamic imbalance will produce periodic vibration when the spindle rotates.

7: 24 SK universal toolholder
It means that the taper of the toolholder is 7:24, which is a separate taper surface positioning, and the taper handle is long. The cone surface plays two important roles at the same time, that is, the accurate positioning of the toolholder relative to the spindle and the clamping of the toolholder.

The tool can be loaded and unloaded quickly without self-locking. As long as the taper angle is machined to a high precision, the connection precision can be ensured, and the cost of the toolholder is relatively low. However, when the spindle rotates at high speed, the taper hole at the front end of the spindle will expand, and the axial displacement of the toolholder will also change. After every tool change, the radial dimension of the tool holder will change, which leads to the instability of the repeated positioning accuracy.

1: 10 HSK vacuum tool holder
The HSK vacuum toolholder relies on the elastic deformation of the toolholder. Not only the 1:10 conical surface of the toolholder contacts with the 1:10 conical surface of the spindle hole of the machine tool, but also the flange surface of the toolholder contacts closely with the spindle surface. This double-sided contact system is superior to the 7:24 universal toolholder in high-speed machining, connection rigidity and coincidence accuracy. HSK toolholder has a variety of specifications, such as A-type, B-type, C-type, D-type, E-type, F-type and so on. Among them, A-type, E-type and F-type are commonly used in vmc850 machining center and have automatic tool change function.

In addition to the transmission groove, there are also manual fixing holes and direction grooves on the A-type toolholder, so the balance is relatively poor. E-type has no transmission groove, so E-type is more suitable for high speed machining. The mechanism of e-type and F-type is exactly the same. The difference between them is that the taper of e-type and F-type toolholders (e.g. E63 and f63) is smaller.

Toolholder is the guarantee of high precision and efficient operation of vmc850 machining center. Only by fully understanding the clamping principle of toolholder, can we be more handy in using CNC machining center.

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Author:

Mr. jiames.wang

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info@qfmh.com

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