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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-07-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000014637</issuerCik>
        <issuerName>BNS CO</issuerName>
        <issuerTradingSymbol>BNSXA.OB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001265093</rptOwnerCik>
            <rptOwnerName>COUCHMAN PARTNERS LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>800 THIRD AVENUE 31ST FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001174448</rptOwnerCik>
            <rptOwnerName>COUCHMAN CAPITAL LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>800 THIRD AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>31ST FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001265094</rptOwnerCik>
            <rptOwnerName>COUCHMAN JONATHAN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>800 THIRD AVENUE 31ST FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock, $.01 par value per share</value>
            </securityTitle>
            <transactionDate>
                <value>2004-07-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>8500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>6.25</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>449500</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Couchman Capital LLC (&quot;Couchman LLC&quot;) is the general partner of Couchman Partners, L.P. (&quot;Couchman LP&quot;) and Jonathan Couchman is the sole member of the Management Board of Couchman LLC. Accordingly, each of Couchman LLC and Mr. Couchman may be deemed to beneficially own the 449,500 shares of Common Stock owned by Couchman LP. Each of Couchman LLC, Couchman LP and Mr. Couchman are deemed to be 10% owners of the issuer. The securities reported in this Form 4 are owned directly by Couchman LP, and owned indirectly by Couchman LLC by virtue of its being the general partner of Couchman LP and by Mr. Couchman by virtue of his position as the sole member of the Management Board of Couchman LLC. Couchman LLC and Mr. Couchman disclaim beneficial ownership of the shares owned by Couchman LP, except to the extent of their pecuniary interest therein.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Couchman Partners, L.P., By: Couchman Capital LLC, its general partner, By: /s/ Jonathan Couchman, Member of Management Board</signatureName>
        <signatureDate>2004-07-15</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Couchman Capital LLC, By: /s/ Jonathan Couchman, Member of Management Board</signatureName>
        <signatureDate>2004-07-15</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Jonathan Couchman</signatureName>
        <signatureDate>2004-07-15</signatureDate>
    </ownerSignature>
</ownershipDocument>

