UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20349

                                  SCHEDULE 13D
                                 (Rule 13d-101)

  INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULE 13d-1 (a) AND
                                   AMENDMENTS
                     THERETO FILED PURSUANT TO RULE 13d-2(a)

                               (Amendment No. 10)*

                             ACME UNITED CORPORATION
                                (Name of Issuer)

     COMMON STOCK, PAR VALUE $2.50 per share (Title of Class of Securities)

                                    004816104
                                 (CUSIP Number)

                                  R. Scott Asen
                                c/o Asen and Co.
                              224 East 49th Street
                            New York, New York 10017
                                  212-758-2323
        (Name, Address, Telephone Number of Person Authorized to Receive
                           Notices and Communications)


                                  May 21, 2004
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d-1(b)(3) or (4), check the following box [ ].

NOTE: Schedules filed in paper format shall include a signed original and five
copies of the Schedule, including all exhibits. See Rule 13d-7(b) for other
parties to whom copies are to be sent.

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).

                                  SCHEDULE 13D

CUSIP NO. 004816104                                                  Page 2 of 5

1        NAME OF REPORTING PERSON
         S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

         R. Scott Asen
         TIN ###-##-####

2        CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*               (A) [ ]

         Not Applicable                                                  (B) [X]

3        SEC USE ONLY


4        SOURCE OF FUNDS*

         PF

5        CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDING IS REQUIRED             [ ]
         PURSUANT TO ITEMS 2(D) OR 2(E)

6        CITIZENSHIP OR PLACE OR ORGANIZATION

         United States of America

                  7        SOLE VOTING POWER
    NUMBER OF
                                    607,690 shares of Common Stock
     SHARES
                  8        SHARED VOTING POWER
  BENEFICIALLY
                                    None
    OWNED BY
                  9        SOLE DISPOSITIVE POWER
     EACH
                                    607,690 shares of Common Stock
   REPORTING
                  10       SHARED DISPOSITIVE POWER
 PERSON WITH
                                    None

11       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                  607,690 shares of Common Stock

12       CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*

                  [ ]

13       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

                  15.9%

14       TYPE OF REPORTING PERSON*

                  IN

*SEE INSTRUCTIONS BEFORE FILLING OUT!

This Amendment No. 10 amends and supplements the Statement on Schedule 13D (the
"Original Statement") filed by R. Scott Asen (the "Reporting Person") with the
United States Securities and Exchange Commission (the "SEC") on March 17, 2000,
as amended on March 24, 2000, April 13, 2000, April 27, 2000, May 9, 2000, June
6, 2000, June 19, 2000, September 15, 2000, February 7, 2001 and June 18, 2001.

ITEM 1. SECURITY AND ISSUER

This Statement relates to the common stock, $2.50 par value ("Common Stock") of
Acme United Corporation (the "Issuer"). The executive offices of the Issuer are
located at 1931 Black Rock Turnpike, Fairfield, Connecticut 06825.

ITEM 2. IDENTITY AND BACKGROUND

      (a) This Statement is being filed by R. Scott Asen (the "Reporting
      Person")

      (b) The principal offices or business address of the Reporting Person is
      c/o Asen and Co., 224 East 49th Street, New York, New York 10017.

      (c) The Reporting Person's principal occupation is President of Asen and
      Co., a New York corporation with principal executive offices located at
      224 East 49th St., New York, New York 10017 ("Asen and Co."), which
      provides certain investment advisory services.

      (d) The Reporting Person has not been convicted in a criminal proceeding
      (excluding traffic violations or similar misdemeanors) during the last
      five years.

      (e) The Reporting Person has not been a party to a civil proceeding of a
      judicial or administrative body of competent jurisdiction during the last
      five years which, as a result of such proceeding, was or is subject to a
      judgment, decree or final order enjoining future violations of, or
      prohibiting or mandating activities subject to, federal or state
      securities laws or finding any violations with respect to such laws.

      (f) The Reporting Person is a citizen of the United States of America.

ITEM 3. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATIONS

The aggregate amount of funds required to purchase the 607,690 shares of Common
Stock owned by the Reporting Person was $1,498,221. The source of funds used by
the Reporting Person to make the purchase of shares of Common Stock was personal
funds.

ITEM 4. PURPOSE OF TRANSACTION

The Reporting Person acquired the Shares for investment purposes. However, the
Reporting Person may hold talks or discussions with various parties, including,
but not limited to, the Issuer's management, its board of directors and other
shareholders on a variety of possible subjects regarding ways to increase
shareholder value. Some of the suggestions the Reporting Person might make may
affect control of the Issuer and/or may relate to the following: the merger,
acquisition or liquidation of the Issuer, the sale or transfer of the assets of
the Issuer, a change in the board of directors or the management of the Issuer,
a change in the present capitalization or dividend policy of the Issuer, a
change in the Issuer's charter or by-laws or any of the other matters referred
to in paragraphs (a) through (j) of the instructions to Item 4 of Schedule 13D.
The Reporting Person intends to pay close attention to developments at and
pertaining to the Issuer, and, subject to market conditions and other factors
deemed relevant by the Reporting Person, the Reporting Person may, directly or
indirectly, purchase additional Shares of the Issuer or dispose of some of such
Shares in open-market transactions or privately negotiated transactions.

ITEM 5. INTEREST IN SECURITIES OF THE ISSUER

As of the date hereof, the Reporting Person has the following interests in the
securities of the Issuer:

      (a) The Reporting Person directly owns 607,690 shares of the Common Stock,
      which shares represent approximately 15.9% of the issued and outstanding
      shares of Common Stock, based on the total number of issued and
      outstanding shares of Common Stock being 3,818,812 (the "Total Outstanding
      Shares"), as reported by the Issuer in its Report on Form 10-Q for the
      quarter ended March 31, 2004.

      (b) The Reporting Person has sole voting, investment and dispositive power
      as to the 607,690 shares of Common Stock directly owned by him.

      (c) No transactions in the Common Stock of the Issuer were effected by the
      Reporting Person, directly or indirectly, during the past sixty days.

      (d) Other than as disclosed herein, no other person has the right to
      receive or the power to direct the receipt of dividends from, or the
      proceeds from the sale of, the shares of Common Stock acquired by the
      Reporting Person.

      (e) Not applicable.

ITEM 6. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT TO
SECURITIES OF THE ISSUER

There exist no contracts, arrangements, understandings or relationships (legal
or otherwise) between the Reporting Person and any other persons with respect to
any securities of the Issuer, including but not limited to transfer or voting of
any such securities, finder's fees, joint ventures, loan or option arrangements,
puts or calls, guarantees of profits, division of profits or loss, or the giving
or withholding of proxies.

ITEM 7. MATERIAL TO BE FILED AS EXHIBITS

Not applicable.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify
that the information set forth in the statement is true, complete and correct.

Dated: May 21, 2004

                                    /s/  R. Scott Asen
                                    ------------------------------
                                         R. Scott Asen