DE732827C - Expanding mandrel for grinding bores - Google Patents

Description

Expanding mandrel for grinding bores For grinding bores So-called expanding mandrels are used, which are made of a highly expandable material, in particular consist of gray cast iron or steel. These spines usually have three or more Milled longitudinal grooves and also a conical longitudinal bore. For grinding The expanding mandrel is used to drill a hole in a workpiece to a certain extent Addition of an abrasive suspended in a liquid to the bore introduced and this by a back and forth going and at the same time rotating movement of the hollow mandrel gradually ground up. To the extent that the hole expanded, the hollow mandrel is drawn in by pulling in a corresponding conical expansion body spread into its conical longitudinal bore and thereby the continuation of the grinding process allows drilling the workpiece. The milling of the longitudinal grooves increases the entire expansion possibility of the expanding mandrel.

Naturally, these expanding mandrels are subject to a fairly considerable amount Wear, so that they have to be renewed very often. To the wear resistance, To .erhöhen such mandrels, attempts were made with a wear-resistant jacket made of hard metal alloys, preferably made of tungsten carbide-cobalt alloys. However, a disadvantage of such encased mandrels was felt that with the available standing means the thorns are not sufficiently spread and accordingly with the thorns only made a much smaller number of holes of different diameters could become. The cause was in the compared to iron alloys much less, "he found the possibility of stretching hard metal alloys.

For non-expandable grinding wheels, the use of a Carbide disc known as an abrasive carrier.

In order to utilize the high wear resistance of the hard metal alloys and to bring the same time but the scope of such components fitted with a coat of a hard metal alloy pins to approximately the same range as steel and cast iron loading stationary mandrels, in an expanding mandrel for Aufschleifen of bores in which the hollow core body consisting of a good stretchable material, having longitudinal grooves, is enclosed by a jacket serving as an abrasive carrier and allowing the core body to expand a ductile metal or a ductile alloy core.

By subdividing and arranging the: jacket in this way it is achieved that in the course of the use of the mandrel become necessary Expansion of the same of the coat can be sure of what, on the other hand, not the The case would be if the contact surfaces of the jacket segments between the longitudinal grooves of the hollow mandrel would be because then namely the possibility of expansion of the mandrel on the longitudinal grooves through the unyielding segment parts lying above them like a bridge would be disabled.

The drawing shows an exemplary embodiment of one according to the invention trained expanding mandrel shown schematically in cross section.

The mandrel consists of a core body having a conical bore i 2 made of an easily expandable material, such as steel or gray cast iron, in the four longitudinal grooves 3 are milled. The core body is covered by a hard metal alloy jacket enclosed, which consists of four segments 1. joined to one another. The latter are so arranged on the core body 2 that their contact surfaces 5 over the longitudinal grooves 3 lie. The connection between the hollow core body and the segmented one Sheath can be done by soldering with copper. During the soldering process you can the ducks are pressed to the core by laying a wire and are in their position held «-erden. In order to avoid the segments being soldered together, between they are allowed a distance of a few millimeters. But if it is required that the jacket segments are as close to one another as possible can be interposed prior to soldering the contact surfaces of the segments a correspondingly thinly scraped carbon plate that the penetration of the copper and the soldering of the Segmcnttcilc counteracts each other.

The number, width and depth of the grooves to be milled in the core body depends on the diameter of the mandrel and the total expansion desired. If particularly long expanding mandrels are to be provided with sheaths made from a hard metal alloy are difficult to manufacture because of the risk of warping during sintering the jackets can also be soldered in several parts perpendicular to the longitudinal axis will.

If when using the mandrel instead of the loose abrasive grain If you want to work with bonded abrasive grain, you can use the in Segments split shell also used hard metal alloys «-erden, in the Grits of abrasives, e.g. B. corundum, silicon carbide, titanium carbide, boron carbide or diamond.

Claims (1)

PATENT CLAIM: Expanding mandrel for grinding Bolirungen, in which the elongated grooves on the iron, hollow core body, which is made of an easily expandable material from one which serves as an abrasive carrier and allows the core body to be injected Sheath is enclosed, characterized in that the sheath is made of a hard metal alloy and is composed of segments that are attached to the core body are i z. B. by soldering) that their contact surfaces over the longitudinal grooves of the core body liegcti.