-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 2M8EhdZ49KIEiqbrfJW2KA==

<SEC-DOCUMENT>0001026608-04-000023.txt : 20040422
<SEC-HEADER>0001026608-04-000023.hdr.sgml : 20040422
<ACCEPTANCE-DATETIME>20040422112823
ACCESSION NUMBER:		0001026608-04-000023
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040421
FILED AS OF DATE:		20040422

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ACME UNITED CORP
		CENTRAL INDEX KEY:			0000002098
		STANDARD INDUSTRIAL CLASSIFICATION:	CUTLERY, HANDTOOLS & GENERAL HARDWARE [3420]
		IRS NUMBER:				060236700
		STATE OF INCORPORATION:			CT
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1931 BLACK ROCK TURNPIKE
		CITY:			FAIRFIELD
		STATE:			CT
		ZIP:			06825
		BUSINESS PHONE:		2033327330

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ACME SHEAR CO
		DATE OF NAME CHANGE:	19710713

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			JOHNSEN WALTER C
		CENTRAL INDEX KEY:			0001014360
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-07698
		FILM NUMBER:		04747313

	BUSINESS ADDRESS:	
		STREET 1:		ACME UNITED CORP
		STREET 2:		1931 BLACK ROCK TURNPIKE
		CITY:			FAIRFIELD
		STATE:			CT
		ZIP:			06825
		BUSINESS PHONE:		2033327330

	MAIL ADDRESS:	
		STREET 1:		C/O ACME UNITED CORP
		STREET 2:		1931 BLACK ROCK TURNPIKE
		CITY:			FAIRFIELD
		STATE:			CT
		ZIP:			06825
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-04-21</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000002098</issuerCik>
        <issuerName>ACME UNITED CORP</issuerName>
        <issuerTradingSymbol>ACU</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001014360</rptOwnerCik>
            <rptOwnerName>JOHNSEN WALTER C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ACME UNITED CORP</rptOwnerStreet1>
            <rptOwnerStreet2>1931 BLACK ROCK TURNPIKE</rptOwnerStreet2>
            <rptOwnerCity>FAIRFIELD</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06825</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President &amp; CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-04-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>75000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.75</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>427272</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.75</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-04-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>75000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.75</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2006-01-22</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>75000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>160000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The stock options became exercisable in three installments
25,000 shares on January 23, 1996
25,000 shares on July 24, 1996
25,000 shares on January 1, 1997</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Walter C. Johnsen</signatureName>
        <signatureDate>2004-04-22</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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