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                                   EXHIBIT 4.1



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                 FOURTH AMENDMENT TO THE NOTE PURCHASE AGREEMENT

         This Fourth Amendment to the Note Purchase Agreement (this "Fourth
Amendment") dated as of October 20, 1999 between ATCHISON CASTING CORPORATION
(the "Company") and TEACHERS INSURANCE AND ANNUITY ASSOCIATION OF AMERICA (the
"Holder");

                              W I T N E S S E T H:

         WHEREAS, the Company and the Holder have heretofore executed and
delivered a Note Purchase Agreement dated as of July 29, 1994 (as amended by the
First Amendment, the Second Amendment, the Third Amendment and the Letter
Agreement described below, the "Note Purchase Agreement") pursuant to which the
Holder purchased $20,000,000 in aggregate principal amount of the Company's
8.44% Senior Notes due July 29, 2004 (the "Notes"); and

         WHEREAS, the Company and the Holder have heretofore executed and
delivered a First Amendment to the Note Purchase Agreement dated as of March 8,
1996 (the "First Amendment"); and

         WHEREAS, the Company and the Holder have heretofore executed and
delivered a Second Amendment to the Note Purchase Agreement dated as of May 24,
1996 (the "Second Amendment"); and

         WHEREAS, the Company and the Holder have heretofore executed and
delivered a Third Amendment to the Note Purchase Agreement dated as of April 3,
1998 (the "Third Amendment"); and

         WHEREAS, the Company and the Holder have heretofore executed and
delivered a Letter Agreement to the Note Purchase Agreement dated as of October
12, 1998 (the "Letter Agreement"); and

         WHEREAS, the Company and the Holder desire to further amend the Note
Purchase Agreement as provided herein;

         NOW, THEREFORE, for good and valuable consideration the receipt of
which is hereby acknowledged, the parties hereto agree that the Note Purchase
Agreement shall be and hereby is amended as follows:

         1. The definition of "Subsidiary" appearing in SECTION 9.1 of the Note
Purchase Agreement is hereby amended in its entirety and as so amended shall
read as follows:


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         SUBSIDIARY: with respect to any Person, any corporation more than 50%
         of the Voting Stock of which (or, solely for purposes of any reference
         to the term "Subsidiary" in SECTION 6.5, more than 60% of the Voting
         Stock of which) is at the time owned by, and the managerial and
         operational control of which is maintained by, such Person and/or one
         or more of its other Subsidiaries. Unless otherwise specified, any
         reference to a Subsidiary is intended as a reference to a Subsidiary of
         the Company; PROVIDED that for purposes of calculating compliance with
         SECTIONS 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.8 and 6.20, Fonderie d'Autun,
         a French corporation, shall not be deemed a Subsidiary to the Company.

         2.      SECTION 6.5(d) of the Note Purchase Agreement is hereby amended
by inserting the following phrase immediately prior to the ";" appearing at the
end thereof:

          "; PROVIDED that the Company will not, and will not permit any of its
         Subsidiaries to, directly or indirectly (through a Subsidiary or
         otherwise) increase its Investment in Fonderie d'Autun, a French
         corporation, above the amount outstanding on October 20, 1999 without
         the consent of the Holder."

         3.      SECTION 6.6 of the Note Purchase Agreement is hereby amended
by adding the following new paragraph at the end thereof:

         Notwithstanding anything in this SECTION 6.6 to the contrary, the
         Company will not and will not permit any of its Subsidiaries to make or
         become obligated to make any Restricted Investment in Fonderie d'Autun,
         a French corporation, without the consent of the Holder.

         4. The Company hereby represents and warrants to the Holder that the
representations and warranties with respect to the Company contained in the Note
Purchase Agreement are true and correct in all material respects and the Holder
shall be entitled to rely on such representations and warranties as if they were
made to the Holder in this Amendment as of the date hereof.

         5. This Fourth Amendment shall become effective upon execution and
delivery of this Fourth Amendment.



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         This Fourth Amendment may be executed in any number of counterparts and
by each party hereto on separate counterpart signature pages, each of which when
so executed shall be an original but all of which shall constitute one and the
same instrument. Except as specifically amended and modified hereby, all of the
terms and conditions of the Note Purchase Agreement shall remain unchanged and
in full force and effect. All references to the Note Purchase Agreement in any
document shall be deemed to be references to the Note Purchase Agreement as
amended hereby. All capitalized terms used herein without definition shall have
the same meaning herein as they have in the Note Purchase Agreement.

         This Fourth Amendment shall be construed and governed by and in
accordance with the laws of the State of New York.

         Dated as of the date first above written.

                          ATCHISON CASTING CORPORATION



                         By /s/ Kevin T. McDermed
                            ------------------------------
                             Name: Kevin T. McDermed
                             Title: V.P. & Treasurer



                         TEACHERS INSURANCE AND ANNUITY
                             ASSOCIATION OF AMERICA



                         By /s/ Loren S. Archibald
                            -------------------------------
                            Name: Loren S. Archibald
                            Title: Managing Director