Tool holder

TOOL HOLDER

Tool holder is a kind of tool for connecting mechanical spindle with tools and other accessories. At present, main standards include BT, SK, CAPTO, BBT, HSK and other spindle models.

Standard editor

At present, the main standards are BT, SK, CAPTO, BBT, HSK and other specifications of the spindle model.

BT, BBT, are Japanese standards, is now a widely used standard. SK (DIN6987) German standard

Traditional shank, ER type, strong type, side solid type, plane milling cutter type, drill chuck, Morse taper shank

Modern hydraulic handle, hot expansion handle, PG (cold pressing).

Accuracy and effect editing

BT, SK, is a simple, popular spindle shank connection standard, mainly BT30, BT40, BT50, SK30... And so on. Die industry, and high - speed engraving machine, used more.

7/24 taper shank editing

For more than half a century, the BT shank with 7/24 taper has been used in the machining center to connect the tool and the spindle of the machine tool. The standard 7/24 cone connection has many advantages, such as: it enables fast tool handling; Under the action of the axial tension of the pull rod, the taper of the tool handle is in close contact with the inner cone of the spindle. The solid cone directly supports the tool in the cone hole of the spindle, which can reduce the overhang of the tool. Only one size needs to be machined to high accuracy, so the cost is low and reliable. However, with the development of high-speed cutting, cutting tools to be much higher than before under the speed of cutting, BT handle connection performance on the following major deficiencies, figure 2

FIG. 2 working diagram of BT tool system during high-speed machining

FIG. 2 working diagram of BT tool system during high-speed machining

Is the working diagram of BT tool system during high-speed machining:

(1) spindle and shank cannot be positioned at the same time with spindle end face and inner cone face, resulting in low connection stiffness, especially at high rotating speed. Due to the action of centrifugation, the expansion amount of spindle cone is larger than that of small end, which reduces the contact area of tool shank and spindle, and the radial stiffness of tool system, and reduces the positioning accuracy.

(2) under the high speed rotating (especially after of more than 8000 RPM), under the action of centrifugal force the handle outward expansion volume and the expansion of the spindle hole quantity difference to be markedly, and the orifice area expansion difference than the handle at the rear of the pull rod, under the action of the handle move back to the axial position change, affects the machining accuracy and stable cutting condition of tools. After the main shaft is stopped, the radial elasticity of the tool handle and the main shaft returns, which makes it easy for the tool handle to get stuck in the main shaft and difficult to remove.

(3) the expansion of the spindle will cause deviation of the center of mass of the cutter and clamping mechanism, which will affect the dynamic balance of the spindle.

(4) the tool handle is of solid long taper handle structure, so it has high quality. When applied in the machining center, the tool changing speed is slow, resulting in long non-processing time.

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