TIPPED CUTTERS

Abstract: A tipped cutter comprises a body (10) which is formed with a plurality of bores (18) into which tapered pins (20) of abrasion-resistant material are placed (with their wider ends inwards), whereafter the regions of the body (10) around the pins are compressed to trap the pins in position. The cutter body (10) is then preferably subjected to hardening. The pins may be further retained in position by brazing, which is activated when the body (10) is heated in a furnace, but because the pins are now trapped in position the gas pressures generated from the brazing are prevented from displacing the pins.

Description: TIPPED CUTTERS This invention relates to tipped cutters for use in an appliance which is used for preparing floor or ground surfaces by e.g. grinding or roughening. Appliances are known for use in grinding or roughening concrete or asphalt surfaces for example, the appliances comprising a unit which is mounted on wheels and houses a number of transverse shafts (e.g. -\ shafts) each mounting a large number of generally star- shaped cutter wheels. The appliance includes a motor for driving the shafts so that the cutters grind or roughen the surface on which the appliance stands. The cutters are provided with tips of tungsten carbide and hitherto these tips have consisted of cylindrical, parallel-sided pins of tungsten carbide inserted into bores drilled radially into the cutter body, the tung¬ sten carbide pins being retained in their bores either by brazing or by an epoxy resin. However, as a result of the use to which the cutters are subjected, in time the tungsten carbide pins loosen and the cutters have to be reDlaced. We have now devised a tipped cutter in which the tips are more securely fixed and will remain in place for longer periods of use. In accordance with this invention, there is pro- vided a tipped cutter, comprising a cutter body formed with a plurality of bores which receive respective pins of abrasion-resistant material, each pin being of tapered shape with its wider portion further into its bore than its narrower portion, and the cutter body being compressed in the region of each pin so as to trap the pin in position. Also in accordance with this invention, there is provided a method of making a tipped cutter, comprising forming a cutter body with a plurality of bores, inserting a pin of abrasion-resistant material into each bore, the pin being of tapered shape and inserted with its wider portion further into its bore than its narrower portion, and compressing the cutter body in the region of each pin so as to trap the pin in position. Preferably the tips comprise tungsten carbide. The cutter body may be formed by forging from mild steel, then drilled to receive the pins. After compressing the cutter body in the regions of the pins when inserted, the cutter body is subjected to hardening and stress relief. Additionally, brazing may be carried out to aid retention of the pins. The brazing is activated when the cutter body is placed into a hydrogen furnace, but because the pins are held in position by the compressed regions of the cutter body, there is no risk of the pins being pushed out of their bores by the pressures of gases developed in these bore by the brazing process. An embodiment of this invention will now be des¬ cribed by way of example only and with reference to the accompanying drawings, in which: FIGURE 1 is a side elevation of a cutter body for a tipped cutter, prior to receiving its tip pins; FIGURE 2 is a view of the edge of the cutter body of Figure 1 in the direction of the arrow A; FIGURE 3 is a side elevation of a tip pin for the cutter; FIGURE 4 is a side elevation of the tipped cutter shown with pins as shown in Figure 3 inserted into the bores of the body shown in Figures 1 and 2 and after regions of the body have been compressed to trap the pins; FIGURE 5 is a section on the line V-V of Figure ~i - and FIGURE 6 is a section on the line VI-VI of Figure . Referring to Figures 1 and 2 of the drawings, there is shown a cutter body or blank 10 for a tipped cutter. The cutter body 10 comprises a generally parallel-sided disc of e.g. mild steel formed with a central, circular aperture 12 for receiving a shaft on which the cutter will be mounted in the appliance in which it is to be fitted. The body 10 is further formed with a series of arcuate recesses 14 in its periphery, leaving a plurality of radially projecting regions 16 spaced at equal inter¬ vals around the periphery of the cutter body, so that overall the cutter body is generally star-shaped. In the example shown, there are six such recesses 14 and projecting regions 16. The cutter body or blank 10 is formed, in the example shown, by forging. The blank is then drilled to provide a blind bore 18 extending radially into the blank from its periphery at the centre of each project¬ ing region 16. - H - Into each of the bores 18 of the cutter body shown in Figures 1 and 2, a pin 20 of tungsten carbide is inserted. The pin 20 is shown in Figure 3 and comprises a circular section but tapering element. Each pin 20 is inserted into its bore 18 with its wider end first. When all of the pins are inserted into the bores 18 of the cutter body, the outer regions of the body receiving the pins are compressed in order to trap the pins in position. Thus the cutter body is compressed over a peripheral annular region thereof, and this deforms the regions around the individual pins, as shown in Figure 6. The pins are now securely held in position, with their outer ends projecting a short distance from the cutter body to form abrasion-resistant tips 22 as shown in Figure 4. Thereafter the cutter is subjected to hardening and stress relief before it is ready for use. As men¬ tioned above, the pins may be brazed to the holes in which they are inserted, as an additional means of securement. In this case, the brazing is activated by placing the cutter in a hydrogen furnace prior to cooling and then placing the cutter in the furnace used for the hardening process. However, because the pins are trapped in position by the compression of the adja¬ cent regions of the body, there is no risk of the pins being pushed out by the pressures of gases generated in the brazing process.

Claims: CLAIMS 1) A tipped cutter, comprising a cutter body formed with a plurality of bores which receive respective pins of abrasion-resistant material, each pin being of tapered shape with its wider portion further into its bore than its narrower portion, and the cutter body being compressed in the region of each pin so as to trap the pin in position. 2) A tipped cutter as claimed in claim 1, which is in the form of a disc formed with a series of recesses in its periphery, leaving a plurality of radially projecting regions which are provided with said bores receiving the pins. 3) A tipped cutter as claimed in claim 1 or 2, in which the pins comprise tungsten carbide. 4) A tipped cutter as claimed in claim 1, 2 or 3, in which the cutter body comprises mild steel. 5) A method of making a tipped cutter, comprising forming a cutter body with a plurality of bores, inserting a pin of abrasion-resistant material into each bore, the pin being of tapered shape and inserted with its wider portion further into its bore than its narrower portion, and compressing the cutter body in the region of each pin so as to trap the pin in its position. 6) A method as claimed in claim 5, in which the cutter body is subjected to hardening after the compressing step. 7) A method as claimed in claim 5 or 6, in which razing is carried out to aid retention of the pins in their bores, the brazing being activated when the cutter is heated in a furnace. 8) A method as claimed in claim 5, 6 or 7, in which the pins comprise tungsten carbide * 9) A method as claimed in claim 5, 6, 7 or 8, in which the cutter body comprises mild steel. 10) A tipped cutter substantially as herein described with reference to the accompanying drawings. 11) A method of making a tipped cutter, the method being as claimed in claim 5 and substantially as herein described with reference to the accompanying drawings.

Inventors: GOODE RALPH, GOODE, RALPH
Applicants: GOODE RALPH, INT GRINDING AND ABRASIVES INC, GOODE, RALPH, INTERNATIONAL GRINDING AND ABRASIVES INC.
Application year: 1989
Main classification: B24D18
IPC codes: B24D17, B24D18, B28D1