-----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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 3TRucK2QMwDlUtcNqo5AUA==

<SEC-DOCUMENT>0000100378-03-000015.txt : 20030701
<SEC-HEADER>0000100378-03-000015.hdr.sgml : 20030701
<ACCEPTANCE-DATETIME>20030701145439
ACCESSION NUMBER:		0000100378-03-000015
CONFORMED SUBMISSION TYPE:	5
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030630
FILED AS OF DATE:		20030701

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			JOYCE MICHAEL H
		CENTRAL INDEX KEY:			0001135310

	FILING VALUES:
		FORM TYPE:		5
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-07635
		FILM NUMBER:		03767722

	BUSINESS ADDRESS:	
		STREET 1:		5001 N SECOND ST
		CITY:			ROCKFORD
		STATE:			IL
		ZIP:			61111
		BUSINESS PHONE:		8156396596

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			TWIN DISC INC
		CENTRAL INDEX KEY:			0000100378
		STANDARD INDUSTRIAL CLASSIFICATION:	GENERAL INDUSTRIAL MACHINERY & EQUIPMENT [3560]
		IRS NUMBER:				390667110
		STATE OF INCORPORATION:			WI
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		1328 RACINE ST
		CITY:			RACINE
		STATE:			WI
		ZIP:			53403
		BUSINESS PHONE:		2626384000

	MAIL ADDRESS:	
		STREET 1:		1328 RACINE STREET
		CITY:			RACINE
		STATE:			WI
		ZIP:			53403

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	TWIN DISC CLUTCH CO
		DATE OF NAME CHANGE:	19770217
</SEC-HEADER>
<DOCUMENT>
<TYPE>5
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>

<ownershipDocument>

    <documentType>5</documentType>

    <periodOfReport>2003-06-30</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

    <issuer>
        <issuerCik>0000100378</issuerCik>
        <issuerName>TWIN DISC INC</issuerName>
        <issuerTradingSymbol>TDI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001135310</rptOwnerCik>
            <rptOwnerName>JOYCE MICHAEL H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President, COO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock</value>
        </securityTitle>
        <transactionDate>
            <value>2003-06-30</value>
            <footnoteId id="F1"/>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>5</transactionFormType>
            <transactionCode>I</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>463</value>
            </transactionShares>
            <transactionValue>
                <value>0</value>
                <footnoteId id="F1"/>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>3628</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>D</value>
            </directOrIndirectOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <derivativeSecurity>
        <securityTitle>
            <value>Stock Options</value>
        </securityTitle>
        <conversionOrExercisePrice>
            <value>14.45</value>
        </conversionOrExercisePrice>
        <transactionDate>
            <value>2002-08-02</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>5</transactionFormType>
            <transactionCode>A</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>4000</value>
            </transactionShares>
            <transactionValue>
                <value>14.45</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <exerciseDate>
            <value>2002-08-02</value>
        </exerciseDate>
        <expirationDate>
            <value>2012-08-02</value>
        </expirationDate>
        <underlyingSecurity>
            <underlyingSecurityTitle>
                <value>Common Stock</value>
            </underlyingSecurityTitle>
            <underlyingSecurityShares>
                <value>4000</value>
            </underlyingSecurityShares>
        </underlyingSecurity>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>40500</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>D</value>
            </directOrIndirectOwnership>
        </ownershipNature>
    </derivativeSecurity>

    <footnotes>
        <footnote id="F1">Acquired as part of the company's 401K plan</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Michael H. Joyce</signatureName>
        <signatureDate>2003-07-01</signatureDate>
    </ownerSignature>

</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----