Patent GB-670965-A (GB)
Title: Improvements relating to lapping and grinding tools
Inventor: DICKINSON ERNEST
IPC: B24D18/00
Filed: 1948-12-22
Abstract: 670,965. Electrodeposition of copper and nickel. GUEST, KEEN & NETTLEFOLDS (MIDLAND), Ltd. Dec. 21, 1949 (Dec. 22, 1948 ; . July 27, 1949], Nos. 33002/48 and 19703/49. Class 41. [Also in Group XXIII] A method of manufacturing. the working of a lapping or grinding tool comprises the alternate steps of electrolytically, depositing on the core of the working surface of the tool a plurality of layers of metal and embedding in each layer of metal, by means of a pressing or rolling operation, a layer of abrasive such as diamond dust so as to build up' a plurality of alternate layers of metal and abrasive. The metal layer in which the final layer of abrasive is embedded is preferably of a hard metal such as nickel, whereas the remaining layer or layers are of a soft metal such as copper; an electrolytically deposited coating of hard metal may be provided over the final layer of abrasive. When making lapping tools, the tool is firstly degreased by immersion in hot caustic soda solution, washed, anodically etched for one minute and then again washed. A layer of copper two-thousandths of an inch thick is then electrolytically deposited on the tool. The following solution of electrolyte is used :- Copper cyanide - 4.2 oz. per gallon Sodium cyanide - 5.5 " " " Sodium cyanide (free) 0.9 " " " Rochelle salt - - 9.6 " " " Sodium carbonate - 4.8 " " " This solution is operated at room temperature with a current density of 50 to 100 amps. per square foot. After this layer of copper has been deposited the tool is washed and dried and diamond powder or dust is then embedded into the surface of the copper. A further layer of copper two-thousandths of an inch thick is then deposited on the tool and diamond dust embedded into this layer, the tool being built up so that it comprises four layers of copper each two-thousandths of an inch thick and diamond dust embedded into each layer. After the final layer of diamond dust has been applied to the final layer of copper, the tool is heated to 120‹ C. after which it is placed in the apparatus shown in Fig. 2 in order to plate a layer of nickel on to the tool. The apparatus comprises a bath 10 of heat resistant material mounted on a support 11 over a source of heat 12. The tools 13 to be plated are suspended in the mouth of the bath from a copper rod 14 forming the cathode. The electrolyte contained in the bath 10 is made up as follows :- Nickel chloride - 30 oz. per gallon Boric acid - - 3 ,, ,, ,,  P.H. 1.0 to 5.0 (adjusted with hydrochloric acid). The level of the electrolyte in the bath 10 is adjusted so that it just comes to the shoulder formed between the handle and the working surface of the tool. The anode comprises a cylindrical sheet of pure nickel 17 closely fitting the inside of the bath 10 and surrounding the tools 13. To obtain even plating over the entire working surface of the tools a pipe 18 is disposed within the bath and is connected to a source of air supply so that the electrolyte can be agitated. The nickel layer is of the same thickness as each layer of copper, i.e. twothousandths of an inch; the temperature of the electrolyte is maintained between 55 and 65 ‹ C. using a current density of 50 to 100 amps per square foot. After a layer of nickel has been deposited the tool is again washed and dried and a further layer of diamond dust is then embedded in the nickel. The tool is then again heat treated at 120 C. for approximately three hours; if more than one layer of nickel is to be deposited the second heat treatment is not carried out until the final layer of nickel has been formed. Specification 612,013, [Group XXIII], is referred to.