Exhibit 5.1


                              September 23, 2004


Securities and Exchange Commission
450 5th Street, N.W. Judiciary Plaza
Washington, D.C. 20549

      Re:      Registration Statement on Form S-4 filed by Argo-Tech Corporation
              ------------------------------------------------------------------
              (the "Registration Statement")
              ------------------------------

Ladies and Gentlemen:

         I am the General Counsel of Argo-Tech Corporation, a Delaware
corporation (the "COMPANY"), and have acted as such in connection with the
issuance and exchange (the "EXCHANGE OFFER") of up to $250,000,000 aggregate
principal amount of the Company's 9 1/4% Senior Notes due 2011 (the "EXCHANGE
NOTES") for an equal principal amount of the Company's 9 1/4% Senior Notes due
2011 outstanding on the date hereof (the "OUTSTANDING NOTES"). The Outstanding
Notes have been, and the Exchange Notes will be, issued pursuant to an
Indenture, dated as of June 23, 2004 (the "INDENTURE"), between the Company and
BNY Midwest Trust Company, as Trustee (the "TRUSTEE"). The Outstanding Notes
are, and the Exchange Notes will be, guaranteed (the "GUARANTEES") on a joint
and several basis by each of the following direct and indirect subsidiaries of
the Company: Argo-Tech Corporation (Aftermarket), Argo-Tech Corporation (HBP),
Argo-Tech Corporation (OEM), each of which are Delaware corporations, Argo-Tech
Corporation Costa Mesa, a California corporation and Durodyne, Inc., an Arizona
corporation (collectively, the "GUARANTORS").

         In rendering this opinion, I have examined such documents and records,
including an examination of originals or copies certified or otherwise
identified to my satisfaction, and matters of law as I have deemed necessary for
purposes of this opinion. Based upon the foregoing and subject to the
assumptions, qualifications and limitations stated herein, I am of the opinion
that:

         1. When the Registration Statement becomes effective under the
Securities Act of 1933 and the Exchange Notes are executed by the Company,
authenticated by the Trustee in accordance with the Indenture and delivered in
accordance with the terms of the Exchange Offer in exchange for the Outstanding
Notes, the Exchange Notes will be validly issued by the Company and will
constitute valid and binding obligations of the Company; and

         2. When the Registration Statement becomes effective under the
Securities Act of 1933 and the Guarantees of the Exchange Notes (the "EXCHANGE
GUARANTEES") are delivered in accordance with the terms of the Exchange Offer in
exchange for the Guarantees of the Outstanding Notes, the Exchange Guarantees of
the Guarantors will have been validly issued by each of the Guarantors and will
constitute a valid and binding obligation of each respective Guarantor.


Securities and Exchange Commission
September 23, 2004
Page 2 of 2



         My opinions are limited by bankruptcy, insolvency, reorganization,
fraudulent transfer, fraudulent conveyance, voidable preference, moratorium or
other similar laws, regulations or judicial opinions of general applicability
relating to or affecting creditors' rights generally, and by general equitable
principles, whether such principles are considered in a proceeding at law or at
equity.

         I am admitted to practice law in the State of Kentucky and have been
granted corporate status in the State of Ohio to perform legal services on
behalf of the Company. Accordingly, the opinions expressed herein are limited to
the Delaware General Corporation Law (the "DGCL"), the laws of the State of
Kentucky and the laws of the State of Ohio, in each case as currently in effect.
I express no opinion as to the effect of the laws of any other jurisdiction.

         I hereby consent to the filing of this opinion as Exhibit 5.1 to the
Registration Statement and to the reference to me under the caption "Legal
Matters" in the Prospectus constituting a part of the Registration Statement. In
giving such consent, I do not hereby admit that I am included in the category of
persons whose consent is required under Section 7 of the Securities Act of 1933
or the rules and regulations of the Securities and Exchange Commission
promulgated thereunder.

                                          Very truly yours,



                                          /s/ Paul R. Keen
                                          ----------------------
                                          Paul R. Keen
                                          General Counsel