This invention relates to a mounting means for securing alternative grinding wheels to the output shaft of a portable rotary grinding machine, in which a threaded clamping means is used for cooperation with a threaded portion of the output shaft.

This new type of mounting means is intended to meet the securing requirements set up both for so called depressed centre grinding wheels and for plane cutting wheels.

The new mounting means comprises a hub and two alternative clamping elements and is intended to accomplish both an outer annular clamping zone for cutting wheels and an inner annular clamping zone for depressed centre wheels.

According to the securing requirements, each type of grinding wheel shall be clamped between a set of annular clamping surfaces which rise above surrounding portions of the hub and the clamping elements, respectively, by at least 0.5 mm. The difference between the two sets of clamping surfaces is that the clamping surfaces intended for the cutting wheel have to be larger in diameter than the clamping surfaces for the depressed centre wheel.

A preferred embodiment of the invention is shown on the accompanying drawings.

On the drawings:

Fig 1 shows a longitudinal section through the mounting device according to the invention when securing a

depressed centre wheel.

Fig 2 shows a similar section as in Fig 1 but illustrates a plane cutting wheel being secured.

Fig 3 shows a longitudinal section through the front part of the output shaft and the support hub.

Fig 4a shows a longitudinal section through the clamping element intended for depressed centre wheels.

Fig 4b shows a longitudinal section through a clamping element intended for cutting wheels.

Fig 5 shows an end view of the support hub shown in Fig 3.

The new mounting means shown in the drawing figures comprises a support hub 10 rigidly mounted on the output shaft 11 of a rotary grinding machine. The support hub 10 is coupled to the shaft 11 by a tapered socket portion 12 and a woodruff key 15. As being apparent from Figs 3 and Fig 5, the support hub 10 is formed with an inner annular contact surface 13 and an outer annular contact surface 14. The outer and inner contact surfaces 13, 14 are spaced from each other by a annular groove 16 which is at least 0.5 mm deep from any of the contact surfaces 13, 14. In the illustrated embodiment of the invention, the outer contact surface 14 protrudes in front of the inner contact surface 13 by a distance of about 0.5 mm.

As an axial continuation of the tapered socket portion 12, the hub 10 is formed with a cylindrical socket 17 which is open at the front end of the hub. The opening

end of the socket 17 is surrounded by a tubular extension 18 which protrudes axially in front of both the inner and outer contact surfaces 13, 14 so as to form a centering portion for the grinding wheels.

In Fig 4a there is shown a flanged clamping element 20 which is formed with an annular contact surface 21 of a size equal to the inner contact surface 13 of the hub 10. The clamping element 20 also comprises an axially extending neck portion 22 which is intended to fit snugly in the socket 17 of the hub 10.

In Fig 4b there is shown another clamping element 23 which is formed with a radial flange on which there is an annular contact surface 24 of a size equal to the outer contact surface 14 of the hub 10. This clamping element 23 also comprises an axially extending neck portion 25 which is intended to fit snugly in the socket 17 of the hub 10.

As being illustrated in Figs 4a and 4b, both of the clamping elements 20, 23 are provided with a stepped bore 26 and 27, respectively, through which a clamping screw 28 extends to engage a threaded bore 29 in the output shaft 11 of the grinding machine.

In this embodiment of the invention there is illustrated a difference in axial levels between the inner contact surface 13 and the outer contact surface 14 of the support hub, a difference which is designated by the letter A. This difference is about 0.5 mm and ensures that the inner contact surface 13 normally does not reach the plane cutting wheel as the latter is mounted as illustrated in Fig 2. This is to prevent small particles

like grindings from being jammed between the cutting wheel and the surface 13 and, thereby, cause bending forces on the latter. Instead, the cooperation between the outer contact surface 14 of the hub 10 and the contact surface 24 of the clamping element 23 ensures a large diameter clamping zone by which the cutting wheel is firmly supported.

When using the new mounting means for securing a depressed centre wheel as illustrated in Fig 1, the inner contact surface 13 of the support hub 10 cooperates with the contact surface 21 of the smaller clamping element 20 to obtain an annular clamping zone having the same dimensions as the inner contact surface 13.

In both applications, the clamping force exerted on the grinding wheels is accomplished by the central clamping screw 28.

It is to be noted that the invention is not limited to the above described embodiment, especially concerning the means for securing the support hub onto the output spindle of the rotary grinding machine, but may be adapted to the actual type of grinding machine.