<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-12-08</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000313180</issuerCik>
        <issuerName>KEYCO BOND FUND INC</issuerName>
        <issuerTradingSymbol>N/A</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001314343</rptOwnerCik>
            <rptOwnerName>Keywell Barbara J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>27777 FRANKLIN ROAD, SUITE 1630</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SOUTHFIELD</rptOwnerCity>
            <rptOwnerState>MI</rptOwnerState>
            <rptOwnerZipCode>48034</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $2.04 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2021-12-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>247</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2991</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>As Trustee</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">These 247 shares which were held in the Living Trust of Thomas E. Purther u/a/d August 22, 1985 for which Barbara J. Keywell served as trustee were transferred to the Thomas E. Purther Property Trust u/a/d August 9, 2021 for which Thomas E. Purther is trustee and beneficiary.</footnote>
        <footnote id="F2">On May 5, 2015, Keyco Bond Fund, Inc. implemented a 1 for 102 reverse stock split for its common stock.  Par value for the common stock was increased by a proportionate amount.</footnote>
        <footnote id="F3">Shares held as follows:  (1) 2,340 shares (238,682 shares prior to the reverse stock split) by Living Trust of Barbara J. Keywell u/a/d June 20, 1974, as amended, for which Barbara J. Keywell serves as trustee, (2) 525 shares (53,150 shares prior to the reverse stock split plus 4 shares purchased on June 22, 2016) by Living Trust of Elizabeth K. Purther u/a/d August 22, 1985 for which Barbara J. Keywell serves as trustee and (3) 126 shares (12,530 shares prior to the reverse stock split plus 4 shares purchased on June 22, 2016) by Living Trust of Anthony M. Purther u/a/d August 22, 1985 for which Barbara J. Keywell serves as trustee.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Barbara J. Keywell by Carol Singer, attorney-in-fact</signatureName>
        <signatureDate>2021-12-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
