EXHIBIT 99.3 CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002 In connection with the Quarterly Report on Form 10-Q of Chicago Rivet & Machine Co. (the "Company") for the quarterly period ended March 31, 2003 as filed with the Securities and Exchange Commission on the date hereof (the "Report"), I, John C. Osterman, as Chief Financial Officer of the Company, hereby certify, pursuant to 18 U.S.C. ss. 1350, as adopted pursuant to ss. 906 of the Sarbanes-Oxley Act of 2002, that, to the best of my knowledge: (1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and (2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company. /s/ John C. Osterman - ----------------------------- Name: John C. Osterman Title: Chief Financial Officer Date: May 5, 2003 This certification accompanies the Report pursuant to ss. 906 of the Sarbanes-Oxley Act of 2002 and shall not, except to the extent required by the Sarbanes-Oxley Act of 2002, be deemed filed by the Company for purposes of ss.18 of the Securities Exchange Act of 1934, as amended. A signed original of this written statement required by Section 906 has been provided to Chicago Rivet & Machine Co. and will be retained by Chicago Rivet & Machine Co. and furnished to the Securities and Exchange Commission or its staff upon request. 19