<PAGE>   1

                                                                   EXHIBIT 10.29

                      FIRST AMENDMENT TO CREDIT AGREEMENT

     THIS FIRST AMENDMENT TO CREDIT AGREEMENT, dated as of November 10, 1999
(this "First Amendment"), is among Thermadyne Mfg. LLC, a Delaware limited
liability company (the "Company"), Comweld Group Pty. Ltd. (the "Initial
Australian Borrower"), GenSet S.p.A. (the "Initial Italian Borrower"),
Thermadyne Welding Products Canada Limited (the "Initial Canadian Borrower"),
the various financial institutions listed on the signature pages hereto
(collectively, the "Lenders"), DLJ Capital Funding, Inc. ("DLJ"), as syndication
agent for the Lenders (the "Syndication Agent"), Societe Generale, as
documentation agent for the Lenders (the "Documentation Agent"), and ABN AMRO
Bank N.V. ("ABN AMRO"), as administrative agent for the Lenders (the
"Administrative Agent"; the Syndication Agent and the Administrative Agent are
sometimes referred to herein as the "Agents" and each as an "Agent").

                                  WITNESSETH:

     WHEREAS, the Borrowers, the Lenders, the Syndication Agent, the
Administrative Agent and the Documentation Agent are parties to a Credit
Agreement, dated as of May 22, 1998 (as heretofore amended, waived or modified,
the "Existing Credit Agreement"); and

     WHEREAS, the Borrowers have requested that the Required Lenders amend the
Existing Credit Agreement in certain respects to, among other things, allow the
Company to restructure certain of its and its Subsidiaries' manufacturing
operations, including the establishment of certain new Foreign Subsidiaries and
the relocation of such operations to locations in Mexico and Asia; and

     WHEREAS, the Required Lenders have agreed, subject to the terms and
conditions hereinafter set forth, to so amend the Existing Credit Agreement as
set forth below (the Existing Credit Agreement, as so amended by this First
Amendment, being referred to as the "Credit Agreement");

     NOW, THEREFORE, in consideration of the agreements herein contained, and
for other good and valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, the parties hereto agree as follows:


<PAGE>   2

                                     PART I


                                 DEFINITIONS

     SUBPART 1.1. Certain Definitions. Unless otherwise defined herein or the
context otherwise requires, terms used in this First Amendment, including its
preamble and recitals, have the following meanings (such meanings to be equally
applicable to the singular and plural forms thereof):

     "Credit Agreement" is defined in the third recital.

     "Existing Credit Agreement" is defined in the first recital.

     SUBPART 1.2. Other Definitions. Unless otherwise defined herein or the
context otherwise requires, terms used in this First Amendment, including its
preamble and recitals, have the meanings ascribed thereto in the Existing Credit
Agreement.

                                    PART II

                                 AMENDMENTS TO
                         THE EXISTING CREDIT AGREEMENT

     Effective on (and subject to the occurrence of) the First Amendment
Effective Date, and in reliance upon the representations and warranties made
herein, the Existing Credit Agreement is hereby amended in accordance with this
Part II. Except as expressly so amended, the Existing Credit Agreement shall
continue in full force and effect in accordance with its terms.

     SUBPART 2.1. Amendments to Section 1.1. Section 1.1 of the Existing Credit
Agreement is hereby amended by inserting the following definitions in such
Section in the appropriate alphabetical sequence:

     "Asian Relocation" means the closure and/or disposition of certain
manufacturing operations of Duxtech Pty, Ltd. and its Subsidiaries
(collectively, "Cigweld") and the relocation of such operations to Indonesia
and/or Malaysia and shall include the establishment of and transfer of any such
operations to a Foreign Subsidiary in connection therewith.

     "Existing Capitalized Lease" means each of those certain domestic
capitalized leases listed on Schedule I hereto for the current term of such
lease, but shall not include any renewal, continuation, extension or replacement
of any such lease.




                                      -2-
<PAGE>   3

     "First Amendment" means the First Amendment to the Credit Agreement, dated
as of November 10, 1999, among the Borrowers, the Lenders signatory thereto, and
the Agents.

     "First Amendment Effective Date" is defined in Subpart 3.1 of the First
Amendment.

     "Junior Subordinated Debt" means junior subordinated debt of the Company
issued pursuant to the New Securities Purchase Agreement, which debt shall have
terms and conditions substantially as set forth in Exhibit A to the First
Amendment and shall have such other terms and conditions and be in a form
satisfactory to the Syndication Agent and the Administrative Agent.

     "Mexican Relocation" means the (i) closure and/or disposition of certain
manufacturing operations of the Mexican Relocation Subsidiaries, (ii) formation
of a Mexican corporation that is a wholly owned Subsidiary of Tweco Products,
Inc., (iii) acquisition, development and construction of a manufacturing
facility by such Subsidiary in or near Hermosillo, Mexico, (iv) relocation of
the operations and equipment of Tweco Products, Inc. to such facility, and (v)
other related transactions incidental thereto.

     "Mexican Relocation Subsidiaries" means each of Tweco Products, Inc., a
Delaware corporation, and its Subsidiaries.

     "New Securities Purchase Agreement" means that certain securities purchase
agreement entered into by and among Holdco, the Company and the purchasers party
thereto, pursuant to which such purchasers agree to purchase (a) (i) Junior
Subordinated Debt or (ii) with the consent of the Administrative Agent and the
Syndication Agent, preferred and/or common stock of a corporate holding company
parent of the Company (such holding company to be formed on terms and conditions
satisfactory to the Administrative Agent and the Syndication Agent), and (b) New
Warrants, which purchase shall result in gross proceeds to the Company of at
least $25,000,000 on or prior to December 31, 1999.

     "New Warrants" means warrants to acquire common stock of Holdco issued
pursuant to the New Securities Purchase Agreement, which warrants shall have
terms and conditions substantially as set forth in Exhibit B to the First
Amendment and shall have such other terms and conditions and be in a form
satisfactory to the Syndication Agent and the Administrative Agent.

     "Relocation Capital Expenditures" means capital expenditures made by the
Company or its Subsidiaries in connection with the Mexican Relocation and the
Asian Relocation, in an aggregate amount not to exceed (i) $16,500,000 in the
case of the Mexican Relocation (less the amount of Relocation Expenses related
to the Mexican Relocation) and (ii) $19,500,000 in the case of the Asian
Relocation (less the amount of Relocation Expenses related to the Asian
Relocation).

     "Relocation Expenses" means costs, expenses and charges not capitalized or
classified as




                                      -3-
<PAGE>   4

capital expenditures incurred by the Company or its Subsidiaries in connection
with the Mexican Relocation and the Asian Relocation, in an aggregate amount not
to exceed (i) $16,500,000 in the case of the Mexican Relocation (less the amount
of Relocation Capital Expenditures related to the Mexican Relocation) and (ii)
$19,500,000 in the case of the Asian Relocation (less the amount of Relocation
Capital Expenditures related to the Mexican Relocation).

     SUBPART 2.2. Amendment to Definition of Applicable Margin. The definition
of Applicable Margin in the Existing Credit Agreement is hereby amended and
restated to read in its entirety as follows:

     "Applicable Margin" means at all times during the applicable periods set
forth below,

     (a) with respect to the unpaid principal amount of each Term-B Loan
maintained as a (i) Base Rate Loan, (A) for each day prior to the First
Amendment Effective Date, 1.25% and (B) for each day on or after the First
Amendment Effective Date, 1.75% per annum and (ii) LIBO Rate Loan, (A) for each
day prior to the First Amendment Effective Date, 2.5% and (B) for each day on or
after the First Amendment Effective Date, 3.0% per annum;

     (b) with respect to the unpaid principal amount of each Term-C Loan
maintained as a (i) Base Rate Loan, (A) for each day prior to the First
Amendment Effective Date, 1.5% and (B) for each day on or after the First
Amendment Effective Date, 2.0% per annum, and (ii) LIBO Rate Loan, (A) for each
day prior to the First Amendment Effective Date, 2.75% and (B) for each day on
or after the First Amendment Effective Date, 3.25% per annum;

     (c) from the Closing Date through (but excluding) the date upon which the
Compliance Certificate for the second full Fiscal Quarter ending after the
Closing Date is delivered by the Company to the Administrative Agent pursuant to
clause (c) of Section 7.1.1, with respect to the unpaid principal amount of each
(i) Swing Line Loan (which shall be borrowed and maintained only as a U.S.
Dollar denominated Base Rate Loan) and each Committed Revolving Loan and Term-A
Loan maintained as a Base Rate Loan, 1.00% per annum, and (ii) Committed
Revolving Loan and Term-A Loan maintained as a LIBO Rate Loan, 2.25% per annum;
and

     (d) at all times after the date of such delivery of the Compliance
Certificate described in clause (c) above, with respect to the unpaid principal
amount of each Swing Line Loan (which shall be borrowed and maintained only as a
U.S. Dollar denominated Base Rate Loan) and each Committed Revolving Loan and
Term-A Loan, by reference to the applicable Leverage Ratio and at the applicable
percentage per annum (i) for each day prior to the First Amendment Effective
Date, as set forth in the Existing Credit Agreement and (ii) for each day on or
after the First Amendment Effective Date, as set forth below under the column
entitled "Applicable Margin for Base Rate Loans", in the case of Base Rate
Loans, or by reference to the applicable Leverage Ratio and at the applicable
percentage per annum set forth below under the column entitled "Applicable
Margin for LIBO Rate Loans", in the case



                                      -4-
<PAGE>   5

of LIBO Rate Loans:

                APPLICABLE MARGIN FOR COMMITTED REVOLVING LOANS,
                        SWING LINE LOANS AND TERM-A LOANS

<TABLE>
<CAPTION>
                                    APPLICABLE        APPLICABLE
                                  MARGIN FOR BASE  MARGIN FOR LIBO
   LEVERAGE RATIO                    RATE LOANS      RATE LOANS
   --------------                 ---------------  ---------------
<S>                               <C>              <C>
GREATER THAN OR EQUAL TO 5.0:1          1.5%           2.75%

GREATER THAN OR EQUAL TO 4.0:1
 AND LESS THAN 5.0:1                    1.25%          2.5%

GREATER THAN OR EQUAL TO 3.0:1
 AND LESS THAN 4.0:1                    0.75%          2.0%

LESS THAN 3.0:1                         0.25%          1.5%
</TABLE>


     The Leverage Ratio used to compute the Applicable Margin for Swing Line
Loans, Committed Revolving Loans and Term-A Loans for any day referred to in
clause (d) above shall be the Leverage Ratio set forth in the Compliance
Certificate most recently delivered by the Company to the Administrative Agent
on or prior to such day pursuant to clause (c) of Section 7.1.1. Changes in the
Applicable Margin for Swing Line Loans, Committed Revolving Loans and Term-A
Loans resulting from a change in the Leverage Ratio shall become effective (as
of the first day following the Fiscal Quarter in respect of which such
Compliance Certificate was required to be delivered) upon delivery by the
Company to the Administrative Agent of a new Compliance Certificate pursuant to
clause (c) of Section 7.1.1. In the event such Compliance Certificate indicates
a Leverage Ratio that would result in an Applicable Margin which is greater or
lesser than the Applicable Margin theretofore in effect, then (A) such greater
or lesser Applicable Margin shall be deemed to be in effect for all purposes of
this Agreement from the first day following the Fiscal Quarter in respect of
which such Compliance Certificate was required to be delivered by the Company to
the Administrative Agent pursuant to clause (c) of Section 7.1.1 and (B) if any
Borrower shall have theretofore made any payment of interest in respect of Swing
Line Loans, Committed Revolving Loans or Term-A Loans, or of Letter of Credit
fees pursuant to the first sentence of Section 3.3.3, in any such case in
respect of the period from the first day following the Fiscal Quarter in respect
of which such Compliance Certificate was required to be delivered to the actual
date of delivery of such Compliance Certificate, then, on the next Quarterly
Payment Date, either (x) if the new Applicable Margin is greater than the
Applicable Margin theretofore in effect, such Borrower shall pay as a
supplemental payment of interest and/or Letter of Credit fees, an amount which
equals the difference between the amount of interest and Letter of Credit fees
that would otherwise have been paid based on such new Leverage Ratio and the
amount of such interest and Letter of Credit fees actually so paid, or (y) if
the new Applicable Margin is less than the Applicable Margin theretofore in
effect, an amount shall be deducted from the interest on Committed Revolving
Loans, commitment fees and Letter of Credit fees (in the case of differences in
respect of interest on



                                      -5-
<PAGE>   6

Committed Revolving Loans and Letter of Credit fees) or from the interest on
Term-A Loans (in the case of differences in respect of interest on Term-A Loans)
thereafter payable by such Borrower in an amount which equals the difference
between the amount of interest and Letter of Credit fees so paid and the amount
of interest and Letter of Credit fees that would otherwise have been paid based
on such new Leverage Ratio (or, if no payment by such Borrower to the Revolving
Lenders or Term-A Lenders, as the case may be, will thereafter accrue hereunder,
or if the amount that so accrues is less than such difference, the Revolving
Lenders or the Term-A Lenders, as the case may be, will promptly pay to such
Borrower an amount equal to such difference less the amount, if any, of such
accrued and unpaid payments); provided, that if the Company shall fail to
deliver a Compliance Certificate within the number of days required pursuant to
clause (c) of Section 7.1.1 (without giving effect to any grace period), the
Applicable Margin for all Committed Revolving Loans, Term-A Loans and Letters of
Credit from and including the first day after the date on which such Compliance
Certificate was required to be delivered to but not including the date the
Company delivers to the Administrative Agent a Compliance Certificate shall
conclusively equal the highest Applicable Margin for the relevant type of Loan
set forth in clause (d) above."

     SUBPART 2.3. Amendment to Definition of Change of Control. Clause (i) of
the definition of Change of Control is hereby amended and restated as follows:

     "(i) the failure of Holdco at any time to own, directly or indirectly, free
and clear of all Liens and encumbrances (other than Liens of the types permitted
to exist under clauses (b), (f) and (i) of Section 7.2.3), all right, title and
interest in 100% of the Capital Stock of the Company other than Capital Stock
issued pursuant to the New Securities Purchase Agreement;"

     SUBPART 2.4. Amendment to Definition of EBITDA. The existing paragraphs (f)
and (g) of the definition of EBITDA of the Existing Credit Agreement are hereby
relettered as paragraphs (g) and (h), respectively, the word "minus" shall be
deleted immediately following clause (e) thereof and a new paragraph is hereby
added to read as follows:

     "plus

          (f) the amount deducted in determining Net Income representing
     expenses and charges incurred on account of Relocation Expenses,

     minus"

     SUBPART 2.5. Amendment to Definition of Excluded Equity Proceeds. The
definition of Excluded Equity Proceeds is hereby amended by (i) adding, at the
end of clause (v) thereof and before the word "or", the phrase "or the issuance
of the New Warrants" and (ii) adding, following the word "Warrants" in clause
(vi) thereof, the expression ", the New Warrants".




                                      -6-
<PAGE>   7

SUBPART 2.6. Amendment to Definition of Fixed Charge Coverage Ratio. Paragraph
(b)(i) of the definition of Fixed Charge Coverage Ratio is hereby amended and
restated as follows:

     "(b) the sum (without duplication) of

          (i) Capital Expenditures actually made during all such Fiscal Quarters
     pursuant to clause (a) of Section 7.2.7 (excluding (x) Relocation Capital
     Expenditures, (y) Capital Expenditures constituting Capitalized Lease
     Liabilities and (z) Capital Expenditures made by way of the incurrence of
     Indebtedness permitted pursuant to Section 7.2.2(c) to a vendor of any
     assets permitted to be acquired pursuant to Section 7.2.7 to finance the
     acquisition of such assets);"

     SUBPART 2.7. Amendment to Definition of Indebtedness. (a) Clause (c) of the
definition of Indebtedness is hereby amended and restated to read as follows:

     "(c) all Capitalized Lease Liabilities; provided that, for the purpose of
calculating the Leverage Ratio, the total amount of Capitalized Lease
Liabilities shall be reduced by an amount equal to the lesser of (x) the amount
of Indebtedness related to Existing Capitalized Leases and (y) $3,800,000;"

     (b) The final sentence of the definition of Indebtedness is hereby amended
and restated to read as follows:

     "For all purposes of this Agreement, (i) the Indebtedness of any Person
     shall include the Indebtedness of any partnership or joint venture in which
     such Person is a general partner or a joint venturer (to the extent such
     Person is liable for such Indebtedness), and (ii) the Junior Subordinated
     Debt shall not constitute Indebtedness."

     SUBPART 2.8. Amendment to Definition of Interest Expense. The definition of
Interest Expense is hereby amended and restated to read as follows:

     "Interest Expense" means, for any period, the aggregate consolidated
interest expense of the Company and its Subsidiaries for such period, as
determined in accordance with GAAP, including (a) financing costs in respect of
any Receivables Transaction and (b) the portion of any payments made in respect
of Capitalized Lease Liabilities allocable to interest expense, but excluding
(to the extent included in interest expense) (x) up-front fees and expenses and
the amortization of all deferred financing costs and (y) for purposes other than
calculating Excess Cash Flow and EBITDA, payments made in respect of Capitalized
Lease Liabilities allocable to interest expense incurred in respect of the
Existing Capitalized Leases."

     SUBPART 2.9. Amendment to Definition of Material Documents. The definition
of Material Documents is hereby amended and restated to read as follows:




                                      -7-
<PAGE>   8

     "'Material Documents' means the Merger Agreement, the Organic Documents of
the Company, the Investors' Agreement and the New Securities Purchase Agreement,
each as amended, supplemented, amended and restated or otherwise modified from
time to time as permitted in accordance with the terms hereof or of any other
Loan Document."

     SUBPART 2.10. Amendment to Article 7.1. Article 7.1 of the Existing Credit
Agreement is hereby amended and restated by adding a new Section 7.1.14 to read
as follows:

     "SECTION 7.1.14. Mexican Relocation. Within 30 days (or, if the Borrowers
shall have commenced such actions within such 30-day period and diligently
pursued the same, such longer period of time as shall be reasonably necessary to
complete such actions) of the date when inventory and equipment of the Mexican
Relocation Subsidiaries having an aggregate value in an amount equal to or
greater than $500,000 have arrived in Mexico, the Borrowers:

     (a) shall have delivered to the Agents all supplements and other documents
necessary in the judgment of the Agents and their counsel to perfect the Liens
granted to the Administrative Agent pursuant to the Security Agreements in
equipment and inventory owned or leased by the Mexican Relocation Subsidiaries
and located or to be located in Mexico;

     (b) shall have caused to be delivered to the Agents from each Mexican
Relocation Subsidiary which owns a Mexican Subsidiary, (i) certificates
evidencing 65% of the issued and outstanding shares of Capital Stock of each
such Mexican Subsidiary, which certificates shall in each case be accompanied by
undated stock powers duly executed in blank and shall be pledged pursuant to a
Pledge Agreement, and (ii) any and all other documents or instruments of further
assurance required to be filed or customarily provided in respect thereof in the
local jurisdiction of each such Mexican Subsidiary, including but not limited to
opinions of foreign counsel; provided, however, that no Subsidiary shall be
required to pledge in excess of 65% of the outstanding voting stock of any
Non-U. S. Subsidiary. If any securities pledged pursuant to a Pledge Agreement
are uncertificated securities, the Agents shall have received confirmation and
evidence satisfactory to each of them that appropriate book entries have been
made in the relevant books or records of a financial intermediary or the issuer
of such securities, as the case may be, or other appropriate steps have been
taken under applicable law resulting in the perfection of the security interest
granted in favor of the Administrative Agent in such securities pursuant to the
terms of the applicable Pledge Agreement; and

     (c) shall have delivered to the Agents an opinion, on or prior to such 30th
day and addressed to the Agents and all Lenders, from Davis Polk & Wardwell,
special New York counsel to the Obligors, in form and substance satisfactory to
the Agents."

     SUBPART 2.11. Amendment to Section 7.2.2. Clause (e) of Section 7.2.2 of
the Existing Credit Agreement is hereby amended and restated to read as follows:




                                      -8-
<PAGE>   9

     "(e) intercompany Indebtedness (i) (x) of any U.S. Subsidiary of the
Company owing to the Company or any Subsidiary or (y) of the Company owing to
any of its U.S. Subsidiaries, and (ii) of any Non-U.S. Subsidiary of the Company
owing to the Company or any U.S. Subsidiary of the Company; provided that in
respect of (A) any such Indebtedness described in this clause (ii), the U.S.
Dollar Equivalent of such Indebtedness (other than any such intercompany
Indebtedness, (w) into which any Investment by the Company or a U.S. Subsidiary
in a Non-U.S. Subsidiary that was outstanding on the First Amendment Effective
Date was converted, (x) incurred to finance any acquisition permitted hereunder,
(y) outstanding on the First Amendment Effective Date or (z) incurred as part
of, or to finance, Relocation Capital Expenditures or Relocation Expenses
incurred by Non-U.S. Subsidiaries) shall not exceed, when taken together with
the aggregate amount at such time of all outstanding Investments made pursuant
to clause (i) of Section 7.2.5 (other than any such Investments (1) into which
any Indebtedness of any Non-U.S. Subsidiary owing to the Company or any U.S.
Subsidiary that was outstanding on the First Amendment Effective Date was
converted, (2) made as part of, or to finance, any acquisition permitted
hereunder, (3) outstanding on the First Amendment Effective Date, (4) made as
part of, or to finance, Relocation Capital Expenditures or Relocation Expenses
incurred by Non-U.S. Subsidiaries or (5) consisting of the contribution by U.S.
Subsidiaries of equipment used at the manufacturing facilities referred to in
clause (iii) of the definition of Mexican Relocation to the Non-U. S.
Subsidiaries that operate such facilities, but only to the extent, in the case
of this clause (5), required or determined by the Company in good faith to be
advisable to avoid adverse Mexican tax consequences) $20,000,000 at any time
outstanding and (B) any such Indebtedness described in this clause (e) which is
owing to the Company or any of its U.S. Subsidiaries, (1) to the extent
requested by the Administrative Agent, such Indebtedness shall be evidenced by
one or more promissory notes in form and substance satisfactory to the Agents
which (except in the case of any such notes held by a Receivables Subsidiary in
connection with a Receivables Transaction) shall be duly executed and delivered
to (and indorsed to the order of) the Administrative Agent in pledge pursuant to
a Pledge Agreement and (2) in the case of any such Indebtedness owed by a Person
other than the Company or a Subsidiary Co-Obligor, such Indebtedness shall not
be forgiven or otherwise discharged for any consideration other than payment
(Dollar for Dollar or, if denominated in a Foreign Currency, the applicable
Currency) in cash unless the Agents otherwise consent;"

     SUBPART 2.12. Amendment to Section 7.2.4. Section 7.2.4 of the Existing
Credit Agreement is hereby amended and restated to read as follows:

     "SECTION 7.2.4. Financial Covenants.

     (a) EBITDA. The Company will not permit EBITDA for the period of four
consecutive Fiscal Quarters ending on the last day of any Fiscal Quarter
occurring during any period set forth below to be less than the amount set forth
opposite such period:



                                      -9-
<PAGE>   10
<TABLE>
<CAPTION>
                               Period                       EBITDA
                               ------                       ------
                       <S>                             <C>
                       Closing Date to 12/30/01        $ 90,000,000
                       12/31/01 to 12/30/02            $100,000,000
                       12/31/02 to 12/30/03            $105,000,000
                       12/31/03 to 12/30/04            $110,000,000
                       12/31/04 to 12/30/05            $120,000,000
                       12/31/05 to 12/30/06            $125,000,000
                       12/31/06 to 12/30/07            $130,000,000
                       12/31/07 and thereafter         $135,000,000
</TABLE>

          provided, that, to the extent the amount of EBITDA for the immediately
          preceding four consecutive Fiscal Quarter period exceeds the amount of
          EBITDA required to be maintained for such four consecutive Fiscal
          Quarter period pursuant to this clause (a), an amount equal to 50% of
          such excess amount may be carried forward to (but only to) the then
          current Fiscal Quarter (any such amount to be certified to the
          Administrative Agent in the Compliance Certificate delivered for the
          last Fiscal Quarter of such four consecutive Fiscal Quarter period).

     (b) Leverage Ratio. The Company will not permit the Leverage Ratio as of
the end of any Fiscal Quarter ending after the Closing Date and occurring during
any period set forth below to be greater than the ratio set forth opposite such
period:

<TABLE>
<CAPTION>
                               Period                  Leverage Ratio
                               ------                  --------------
                       <S>                             <C>
                         Closing Date to 12/30/00           6:00:1:00
                         12/31/00 to 12/30/01               5.75:1.00
                         12/31/01 to 12/30/02               5.25:1.00
                         12/31/02 to 12/30/03               4.25:1.00
                         12/31/03 to 12/30/04               3.50:1.00
                         12/31/04 and thereafter            3.00:1.00
</TABLE>

     (c) Interest Coverage Ratio. The Company will not permit the Interest
Coverage Ratio as of the end of any Fiscal Quarter ending after the Closing Date
and occurring during any period set forth below to be less than the ratio set
forth opposite such period:

<TABLE>
<CAPTION>
                                                Interest Coverage
                      Period                          Ratio
                      ------                    -----------------
<S>                                             <C>
                    Closing Date to 12/30/00        1.55:1.00
                    12/31/00 to 12/30/01            1.55:1.00
                    12/31/01 to 12/30/02            1.85:1.00
                    12/31/02 to 12/30/03            2.25:1.00
                    12/31/03 to 12/30/04            2.70:1.00
                    12/31/04 to 12/30/05            3.00:1.00
                    12/31/05 to 12/30/06            4.00:1.00
                    12/31/06 to 12/30/07            4.50:1.00
                    12/31/07 and thereafter         5.00:1.00
</TABLE>



                                      -10-
<PAGE>   11

     (d) Fixed Charge Coverage Ratio. The Company will not permit the Fixed
Charge Coverage Ratio as of the end of any Fiscal Quarter ending after the
Closing Date to be less than 1.10:1.00."

     SUBPART 2.13. Amendment to Section 7.2.5. Clause (l) of Section 7.2.5 of
the Existing Credit Agreement is hereby amended and restated to read as follows:

     "(l) equity Investments of the Company or any U.S. Subsidiary in Non-U.S.
Subsidiaries (x) outstanding as of the First Amendment Effective Date or (y)
incurred on or after the First Amendment Effective Date, in an aggregate amount
(in the case of this clause (y)) at any time outstanding not to exceed
(exclusive of any such Investments (w) made as part of, or to finance, any
acquisition permitted hereunder, (x) into which any Indebtedness of a Non-U.S.
Subsidiary to the Company or a U.S. Subsidiary that was outstanding on the First
Amendment Effective Date was converted, (y) made as part of, or to finance, the
Asian Relocation or the Mexican Relocation or Relocation Capital Expenditures or
Relocation Expenses incurred by Non-U.S. Subsidiaries or (z) consisting of the
contribution by U.S. Subsidiaries of equipment used at the manufacturing
facilities referred to in clause (iii) of the definition of Mexican Relocation
to the Non-U.S. Subsidiaries that operate such facilities, but only to the
extent, in the case of this clause (z), required or determined by the Company in
good faith to be advisable to avoid adverse Mexican tax consequences)
$20,000,000 less the aggregate principal amount outstanding at such time of
Indebtedness permitted under clause (e)(ii) of Section 7.2.2 (other than any
such intercompany Indebtedness (A) incurred to finance any acquisition permitted
hereunder, (B) into which any Investment by the Company or a U.S. Subsidiary in
a Non-U.S. Subsidiary that was outstanding on the First Amendment Effective Date
was converted, (C) outstanding on the First Amendment Effective Date, and (D)
incurred as part of, or to finance, the Relocation Capital Expenditures or
Relocation Expenses incurred by Non-U.S. Subsidiaries);"

     SUBPART 2.14. Amendment to Section 7.2.6. Clauses (a) and (b) of Section
7.2.6 of the Existing Credit Agreement are hereby amended and restated to read
as follows:

     "(a) the Company will not, and will not permit any of its Subsidiaries to,
declare, pay or make any dividend, distribution or exchange (in cash, property
or obligations) on or in respect of any shares of any class of Capital Stock
(now or hereafter outstanding) of the Company or on any warrants, options or
other rights with respect to any shares of any class of Capital Stock (now or
hereafter outstanding) of the Company (other than (i) dividends or distributions
payable in its common stock or warrants to purchase its common stock, (ii)
dividends or distributions on preferred stock issued




                                      -11-
<PAGE>   12

pursuant to the New Securities Purchase Agreement payable in additional shares
of such preferred stock as provided for in the certificate of designation for
such preferred stock as in effect on the First Amendment Effective Date and
(iii) splits or reclassifications of its stock into additional or other shares
of its common stock) or apply, or permit any of its Subsidiaries to apply, any
of its funds, property or assets to the purchase, redemption, exchange, sinking
fund or other retirement of, or agree or permit any of its Subsidiaries to
purchase, redeem or exchange, any shares of any class of Capital Stock (now or
hereafter outstanding) of the Company or warrants, options or other rights with
respect to any shares of any class of Capital Stock (now or hereafter
outstanding) of the Company;

     (b) the Company will not, and will not permit any of its Subsidiaries to
(i) directly or indirectly, make any payment or prepayment of principal of, or
make any payment of interest on, any Subordinated Note or Junior Subordinated
Debt, on any day other than the stated, scheduled date for such payment or
prepayment set forth in the documents and instruments memorializing such
Subordinated Note or Junior Subordinated Debt, or which would violate the
subordination provisions of such Subordinated Note or Junior Subordinated Debt,
(ii) redeem, purchase or defease any Subordinated Note, Junior Subordinated Debt
or Discount Debenture, or (iii) make any payment of interest on any Junior
Subordinated Debt prior to the maturity date of such Junior Subordinated Debt
other than in additional Junior Subordinated Debt or through accretion to the
principal amount thereof (the foregoing prohibited acts referred to in clauses
(a) and (b) above are herein collectively referred to as "Restricted
Payments");"

     SUBPART 2.15. Amendment to Section 7.2.7. Clause (a) of Section 7.2.7 is
hereby amended and restated to read as follows:

     "(a) The Company will not, and will not permit any of its Subsidiaries to,
make or commit to make Capital Expenditures, except (i) Relocation Capital
Expenditures, plus (ii) in any Fiscal Year, Capital Expenditures which do not
aggregate in excess of $25,000,000 in such Fiscal Year, plus (iii) an additional
aggregate amount equal to $20,000,000 over the term of this Agreement; provided,
however, that to the extent the amount of Capital Expenditures permitted to be
made in any Fiscal Year pursuant to clause (a)(ii) of this Section exceeds the
aggregate amount of Capital Expenditures actually made during such Fiscal Year,
such excess amount (up to an aggregate of 50% of the amount of Capital
Expenditures permitted for such Fiscal Year, without giving effect to this
proviso) may be carried forward to (but only to) the next succeeding Fiscal Year
(any such amount to be certified by the Company to the Agents in the Compliance
Certificate delivered for the last Fiscal Quarter of such Fiscal Year, and any
such amount carried forward to a succeeding Fiscal Year shall be deemed to be
used prior to the Company and its Subsidiaries using the amount of Capital
Expenditures permitted by this Section in such succeeding Fiscal Year, without
giving effect to such carry-forward)."




                                      -12-
<PAGE>   13

                                    PART III

                          CONDITIONS TO EFFECTIVENESS

     SUBPART 3.1. Effective Date. This First Amendment (and the amendments and
modifications contained herein) shall become effective as of November 10, 1999
and shall have retroactive effect from said date, and shall thereafter be
referred to as the "First Amendment," on the date (the "First Amendment
Effective Date") when all of the conditions set forth in this Subpart 3.1 have
been satisfied.

     SUBPART 3.1.1. Execution of Counterparts. The Agents shall have received
counterparts of this First Amendment executed on behalf of the Borrowers, and
the Administrative Agent shall have confirmed to the Borrowers and the
Syndication Agent that it has received from the Required Lenders their
respective executed counterparts hereto.

     SUBPART 3.1.2. Delivery of New Securities Purchase Agreement. The Agents
shall have received counterparts of the New Securities Purchase Agreement, dated
on or before the First Amendment Effective Date, duly executed and delivered by
an Authorized Officer of the Company and the Purchasers, in form and substance
and containing such terms and conditions as are reasonably satisfactory to the
Agents.

     SUBPART 3.1.3. Affirmation and Consent. The Agents shall have received an
affirmation and consent in form and substance satisfactory to them, executed and
delivered by an Authorized Officer of each Obligor (other than the Borrowers)
under the Existing Credit Agreement and related Loan Documents.

     SUBPART 3.1.4. Amendment Fee. The Agents shall have received, for the
account of each Lender signatory hereto on or prior to November 10, 1999 (the
"Fee Calculation Date"), an amendment fee equal to .25% of each such Lender's
Percentage of the Total Exposure Amount as of the Fee Calculation Date and all
other fees, costs and expenses due and payable pursuant to Section 11.3 of the
Credit Agreement, if then invoiced.

     SUBPART 3.1.5. Legal Details, etc. All documents executed or submitted
pursuant hereto shall be satisfactory in form and substance to the Agents and
their counsel. The Agents and their counsel shall have received all information
and such counterpart originals or such certified or other copies or such
materials, as the Agents or their counsel may reasonably request, and all legal
matters incident to the transactions contemplated by this First Amendment shall
be satisfactory to the Agents and their counsel.




                                      -13-
<PAGE>   14
                                    PART IV

                      REPRESENTATIONS AND WARRANTIES, ETC.

     SUBPART 4.1. Representations and Warranties; No Default. In order to induce
the Required Lenders to enter into this First Amendment, the Borrowers hereby
jointly and severally (a) confirm, reaffirm and restate that the representations
and warranties set forth in Article VI of the Existing Credit Agreement and in
each other Loan Document are true and correct in all material respects as of the
date hereof after giving effect to this First Amendment (unless such
representations and warranties are stated to relate to an earlier date, in which
case such representations and warranties shall have been true and correct in all
material respects as of such earlier date) and (b) represent and warrant that,
after giving effect to the First Amendment set forth herein, no Default or Event
of Default has occurred and is continuing.

                                     PART V

                                 MISCELLANEOUS

     SUBPART 5.1. Cross-References. References in this First Amendment to any
Part or Subpart are, unless otherwise specified, to such Part or Subpart of this
First Amendment. References in this First Amendment to any Article or Section
are, unless otherwise specified, to such Article or Section of the Credit
Agreement.

     SUBPART 5.2. Loan Document Pursuant to Credit Agreement. This First
Amendment is a Loan Document executed pursuant to the Credit Agreement and shall
(unless otherwise expressly indicated therein) be construed, administered and
applied in accordance with the terms and provisions of the Credit Agreement,
including Article XI thereof.

     SUBPART 5.3. Counterparts, etc. This First Amendment may be executed by the
parties hereto in several counterparts, each of which shall be deemed to be an
original and all of which shall constitute together but one and the same
Agreement.

     SUBPART 5.4. Governing Law. THIS FIRST AMENDMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

     SUBPART 5.5. Successors and Assigns. This First Amendment shall be binding
upon and inure to the benefit of the parties hereto and their respective
successors and assigns.




                                      -14-
<PAGE>   15

     IN WITNESS WHEREOF, the parties hereto have caused this First Amendment to
be executed by their respective officers hereunto duly authorized as of the day
and year first above written.


                                        THERMADYNE MFG. LLC

                                        By: /s/ JAMES H. TATE
                                           -----------------------------
                                           Title: Senior Vice President &
                                                  Chief Financial Officer

                                        COMWELD GROUP PTY. LTD.

                                        By: /s/ JAMES H. TATE
                                           -----------------------------
                                           Title:



                                        GENSET S.P.A.

                                        By: /s/ JAMES H. TATE
                                           -----------------------------
                                           Title:



                                        THERMADYNE WELDING PRODUCTS
                                        CANADA LIMITED

                                        By: /s/ JAMES H. TATE
                                           -----------------------------
                                           Title:

<PAGE>   16


                                        DLJ CAPITAL FUNDING, INC.,
                                        as the Syndication Agent and as a Lender

                                        By: /s/ DANA F. KLIEN
                                           -----------------------------
                                           Title: Vice President


                                        ABN AMRO BANK N.V.,
                                        as the Administrative Agent and as a
                                        Lender

                                        By: /s/ TOM COMFORT
                                           -----------------------------
                                           Title: Group Vice President


                                        By: /s/ MARY HONDA
                                           -----------------------------
                                           Title: Vice President

                                        SOCIETE GENERALE,
                                        as the Documentation Agent and as a
                                        Lender

                                        By: /s/ CYNTHIA A. JAY
                                           -----------------------------
                                           Title: Managing Director
<PAGE>   17




                    Schedule I: Existing Capitalized Leases

<TABLE>
<CAPTION>
          Lessor                                   Lessee                   Effective Date
---------------------------------        ---------------------              --------------
<S>                                      <C>                                <C>
National Warehouse Investment Co.        Tweco Products, Inc.               June 6, 1988
                                                                            (Amended and
                                                                            restated on
                                                                            August 11, 1988)
</TABLE>


<PAGE>   18




                                                                       EXHIBIT A

                            JUNIOR SUBORDINATED DEBT

                               [see Exhibit 4.15]
<PAGE>   19




                                                                       EXHIBIT B

                                  NEW WARRANTS

                               [see Exhibit 4.14]