<PAGE>


                                                                EXHIBIT 4.3 (iv)

                                BARNES GROUP INC.

                   AMENDMENT NO. 2 TO NOTE PURCHASE AGREEMENT

                                                          As of February 5, 2003

To each of the Current Noteholders
Named in Annex 1 hereto

Ladies and Gentlemen:

        Barnes Group Inc., a Delaware corporation (hereinafter, the "Company"),
together with its successors and assigns, agrees with you as follows:

1.      PRELIMINARY STATEMENTS.

        1.1     NOTE ISSUANCE, ETC.

        The Company issued and sold $25,000,000 aggregate principal amount of
its 7.13% Senior Notes due December 5, 2005 (as may be amended, restated or
otherwise modified from time to time, the "Notes") pursuant to a Note Purchase
Agreement, as amended by Amendment No. 1 to Note Purchase Agreement (the
"Existing Note Agreement" and, as amended by this Amendment No. 2 to Note
Purchase Agreement (this "Amendment Agreement"), the "Note Agreement"), dated as
of December 1, 1995, and entered into by and among the Company and each of the
Purchasers listed on Schedule A attached thereto. The register for the
registration and transfer of the Notes indicates that the Persons named in Annex
1 hereto (collectively, the "Current Noteholders") are currently the holders of
the outstanding principal amount of the Notes as set forth next to such holder's
name in Annex 1.

2.      DEFINED TERMS.

        Capitalized terms used herein and not otherwise defined herein have the
meanings ascribed to them in the Note Agreement.

3.      AMENDMENT.

        Subject to Section 5, the Existing Note Agreement is amended as provided
for by this Amendment Agreement in the manner specified in Exhibit A (the
"Amendment").

<PAGE>


                                       -2-

4.      REPRESENTATIONS AND WARRANTIES OF THE COMPANY.

        To induce you to enter into this Amendment Agreement and to consent to
the Amendment, the Company represents and warrants as follows:

        4.1.    ORGANIZATION, POWER AND AUTHORITY, ETC.

        The Company is a corporation duly incorporated and validly existing in
good standing under the laws of Delaware and has all requisite corporate power
and authority to enter into and perform its obligations under this Amendment
Agreement.

        4.2.    LEGAL VALIDITY.

        The execution and delivery of this Amendment Agreement by the Company
and compliance by the Company with its obligations hereunder: (a) are within the
corporate powers of the Company; and (b) are legal and do not conflict with,
result in any breach of, constitute a default under, or result in the creation
of any Lien upon any Property of the Company under the provisions of: (i) any
charter instrument or bylaw to which the Company is a party or by which the
Company or any of its Property may be bound; (ii) any order, judgment, decree or
ruling of any court, arbitrator or governmental authority applicable to either
the Company or its Property; or (iii) any agreement or instrument to which the
Company is a party or by which the Company or any of its Property may be bound
or any statute or other rule or regulation of any governmental authority
applicable to the Company or its Property.

        This Amendment Agreement has been duly authorized by all necessary
action on the part of the Company, has been executed and delivered by a duly
authorized officer of the Company, and constitutes a legal, valid and binding
obligation of the Company, enforceable in accordance with its terms, except that
enforceability may be limited by applicable bankruptcy, reorganization,
arrangement, insolvency, moratorium, or other similar laws affecting the
enforceability of creditors' rights generally and subject to the availability of
equitable remedies.

        4.3.    NO DEFAULTS.

        No event has occurred and no condition exists that, upon the execution
and delivery of this Amendment Agreement, would constitute a Default or an Event
of Default.

5.      EFFECTIVENESS OF AMENDMENT.

        The Amendment shall become effective as of the first date written above
(the "Effective Date") upon:

<PAGE>

                                       -3-

        (a)     execution and delivery of a counterpart of this Amendment
Agreement by the Company and the holders of 66-2/3% of the aggregate outstanding
principal amount of the Notes;

        (b)     delivery by the Company of a fully executed copy of the Kar
Guaranty (as defined below) dated as of February 5, 2003 from Kar Products, LLC,
a Delaware limited liability company, in favor of (i) Fleet National Bank, a
national banking association, as administrative agent (in such capacity, the
"Administrative Agent") for itself and the other lending institutions
(collectively, the "Bank Lenders") which are or may become parties to a
Revolving Credit Agreement dated as of June 14, 2002 by and among the Company,
the Bank Lenders, the Administrative Agent and the Documentation Agents (as such
term is defined in the Credit Agreement) (the "Credit Agreement"), (ii) each of
the Bank Lenders, (iii) each of the holders of the Notes and (iv) each of the
other financial institutions named therein, guarantying the payment and other
obligations of the Company under the Credit Agreement, the Note Agreement and
the other agreements listed therein (including (x) the Note Purchase Agreement
dated as of November 21, 2000, by and among the Company and each of the
purchasers listed on Exhibit A attached thereto (the "2000 Note Agreement") and
(y) the separate Note Agreements, each dated as of November 12, 1999, by and
among 3031786 Nova Scotia Company, a Nova Scotia company, the Company as
guarantor and each of the purchasers listed on Schedule A attached thereto
(collectively, the "Nova Scotia Agreement")) (the "Kar Guaranty");

        (c)     delivery by the Company of a fully executed copy of (i) an
amendment to the 2000 Note Agreement, dated the date hereof, and (ii) an
amendment to the Nova Scotia Agreement; and

        (d)     delivery by the Company of a fully executed copy of an amendment
to the Credit Agreement, dated the date hereof.

6.      EXPENSES.

        Whether or not the Amendment becomes effective, the Company will
promptly (and in any event within thirty days of receiving any statement or
invoice therefor) pay all fees, expenses and costs relating to this Amendment
Agreement, including, but not limited to, the reasonable fees of your special
counsel, Bingham McCutchen LLP, incurred in connection with the preparation,
negotiation and delivery of this Amendment Agreement and any other documents
related thereto. Nothing in this Section shall limit the Company's obligations
pursuant to Section 1.5 of the Existing Note Agreement.

7.      MISCELLANEOUS.

        7.1.    PART OF EXISTING NOTE AGREEMENT; FUTURE REFERENCES, ETC.

        This Amendment Agreement shall be construed in connection with and as a
part of the Existing Note Agreement and, except as expressly amended by this
Amendment Agreement, all terms, conditions and covenants contained in the
Existing Note Agreement are hereby ratified and shall be and remain in full
force and effect. Any and all notices, requests, certificates and other
instruments executed and delivered after the execution and delivery of this
Amendment Agreement may refer to the Existing Note Agreement without making
specific reference to this

<PAGE>

                                       -4-

Amendment Agreement, but nevertheless all such references shall include this
Amendment Agreement unless the context otherwise requires.

        7.2.    COUNTERPARTS; EFFECTIVENESS.

        This Amendment Agreement may be executed in any number of counterparts,
each of which shall be an original but all of which together shall constitute
one instrument. Each counterpart may consist of a number of copies hereof, each
signed by less than all, but together signed by all, of the parties hereto.
Delivery of an executed signature page by facsimile transmission shall be
effective as delivery of a manually signed counterpart of this Amendment
Agreement.

        7.3.    GOVERNING LAW.

        THIS AMENDMENT AGREEMENT SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE
WITH, AND THE RIGHTS OF THE PARTIES SHALL BE GOVERNED BY, THE LAW OF THE STATE
OF CONNECTICUT EXCLUDING CHOICE-OF-LAW PRINCIPLES OF THE LAW OF SUCH STATE THAT
WOULD REQUIRE THE APPLICATION OF THE LAWS OF A JURISDICTION OTHER THAN
CONNECTICUT.

   [Remainder of page intentionally left blank; next page is signature page.]

<PAGE>

        If you are in agreement with the foregoing, please so indicate by
signing the acceptance below on the accompanying counterpart of this Amendment
Agreement and returning it to the Company, whereupon it will become a binding
agreement among each of you and the Company.

                                          BARNES GROUP INC.

                                          By:    /s/ William C. Denninger
                                          Name:  William C. Denninger
                                          Title: Senior Vice President - Finance
                                                 and Chief Financial Officer

                                          By:    /s/ Lawrence W. O'Brien
                                          Name:  Lawrence W. O'Brien
                                          Title: Vice President and Treasurer

<PAGE>

                                       -2-

        The foregoing Amendment Agreement is hereby accepted as of the date
first above written.

                                          CONNECTICUT GENERAL LIFE
                                          INSURANCE COMPANY
                                          By:    CIGNA Investments, Inc.

                                          By:    /s/ Robert W. Eccles
                                          Name:  Robert W. Eccles
                                          Title: Managing Director


                                          LIFE INSURANCE COMPANY OF
                                          NORTH AMERICA
                                          By:    CIGNA Investments, Inc.

                                          By:    /s/ Robert W. Eccles
                                          Name:  Robert W. Eccles
                                          Title: Managing Director

<PAGE>

                                       -3-

                                          ACE AMERICAN INSURANCE CO.
                                          By:    Stein Roe Farnham Inc., as
                                                 Agent

                                          By:    /s/ Richard A. Hegwood
                                          Name:  Richard A. Hegwood
                                          Title: Senior Vice President

                                          ACE PROPERTY & CASUALTY
                                          INSURANCE COMPANY
                                          By:    Stein Roe Farnham Inc., as
                                                 Agent

                                          By:    /s/ Richard A. Hegwood
                                          Name:  Richard A. Hegwood
                                          Title: Senior Vice President

<PAGE>

                                       -4-

                                          THE LINCOLN NATIONAL LIFE
                                          INSURANCE C0OMPANY

                                          By:    Delaware Investment Advisers,
                                                 a Series of Delaware Management
                                                 Business Trust, its
                                                 Attorney-in-Fact

                                          By:    /s/ Richard Corwin
                                          Name:  Richard Corwin
                                          Title: Vice President

<PAGE>


                                     ANNEX 1

                             CURRENT NOTEHOLDERS AND
                      CURRENT OUTSTANDING PRINCIPAL AMOUNT

<TABLE>
<CAPTION>
Current Noteholders:                             Outstanding Principal Amount of Notes
--------------------                             -------------------------------------
<S>                                              <C>
Connecticut General Life                         $  5,100,000
Insurance Company

Life Insurance Company of                        $  3,750,000
North America

ACE American Insurance Co.                       $  2,594,625

ACE Property & Casualty Insurance Company        $  1,155,375

Lincoln Investment Management, Inc.              $  6,150,000

TOTAL                                            $ 18,750,000
</TABLE>

<PAGE>

                                    EXHIBIT A

                                    AMENDMENT

1.      Section 7.7 (Indebtedness) of the Existing Note Agreement is hereby
amended and restated in its entirety to read as follows:

"Section 7.7    Indebtedness.

        The Company will not, nor will it permit any of its Subsidiaries to,
directly or indirectly incur, create, assume or permit to exist any Indebtedness
other than:

        (a)     Indebtedness incurred by the Company under the Revolving Credit
                Agreement;
        (b)     the Notes;
        (c)     Indebtedness outstanding on the date hereof under the Company's
                $40,000,000, 9.47% Senior Notes due September 16, 2001;
        (d)     Indebtedness of the Company which constitutes extensions,
                renewals or replacements on substantially the same terms and
                conditions (and does not increase the amount outstanding) of (a)
                through (c) above;
        (e)     the Kar Guaranty; and
        (f)     additional Indebtedness of the Company and its Subsidiaries;

        provided, however, that (i) the total Indebtedness of the Company's
        Subsidiaries shall not at any time exceed $100 million (excluding the
        Kar Guaranty); (ii) total Indebtedness of the Company's Domestic
        Subsidiaries (excluding the Kar Guaranty) shall not at any time exceed
        $10 million (excluding from the calculation thereof for all purposes
        except compliance with Section 7.4(b)(4) any pre-existing Indebtedness
        of a newly acquired Domestic Subsidiary for a period not exceeding 30
        days after acquisition of such Domestic Subsidiary); and (iii) the
        aggregate amount of all Indebtedness of the Company and its Subsidiaries
        at any time outstanding shall not exceed an amount equal to 155% of
        Consolidated Net Worth at such time."

2.      Clause (d) of Section 7.14 (Restricted Loans, Advances and Investments)
of the Existing Note Agreement shall be amended and restated in its entirety to
read as follows:

        "(d) loans or advances of the Company to any of its Subsidiaries and
loans or advances of any Subsidiary of the Company to the Company or another
such Subsidiary, or an investment made by the Company in a Person pursuant to
which, immediately after giving effect to such investment, such Person becomes a
Subsidiary of the Company,"

3.      Clause (e) of Section 7.14 (Restricted Loans, Advances and Investments)
of the Existing Note Agreement shall be amended and restated in its entirety to
read as follows:

<PAGE>

                                       -2-

        "(e) in addition to those investments permitted by clause (d) hereof,
purchases of stock or other securities of any corporations, associations or
other business entities; provided, however, that the aggregate cost to or fair
market value of the consideration paid by the Company and its Subsidiaries for
such stock or securities of any such corporation, association or other business
entity shall not exceed 40% of the Company's Consolidated Net Worth within any
four-year period commencing on the Closing Date, or"

4.      The definition of "Kar Guaranty" shall be added to Section 10.1 (Terms
Defined) of the Existing Note Agreement in the appropriate alphabetical order
thereof to read as follows:

""Kar Guaranty" means that certain Guaranty dated as of February 5, 2003 from
Kar Products, LLC, a Delaware limited liability company, in favor of (i) Fleet
National Bank, a national banking association, as administrative agent (in such
capacity, the "Administrative Agent") for itself and the other lending
institutions (collectively, the "Bank Lenders") which are or may become parties
to a Revolving Credit Agreement dated as of June 14, 2002 by and among the
Company, the Bank Lenders, the Administrative Agent and the Documentation Agents
(as such term is defined in the Credit Agreement) (the "Credit Agreement"), (ii)
each of the Bank Lenders, (iii) each of the holders of the Notes and (iv) each
of the other financial institutions named therein, guarantying the payment and
other obligations of the Company under the Credit Agreement, the Note Agreement
and the other agreements listed therein (including (x) the Note Purchase
Agreement dated as of November 21, 2000, by and among the Company and each of
the purchasers listed on Exhibit A attached thereto (the "2000 Note Agreement")
and (y) the separate Note Agreements, each dated as of November 12, 1999, by and
among 3031786 Nova Scotia Company, a Nova Scotia company, the Company as
guarantor and each of the purchasers listed on Schedule A attached thereto
(collectively, the "Nova Scotia Agreement"))."