UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): June 14, 2013 (June 12, 2013)

LUFKIN INDUSTRIES, INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (936) 634-2211

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Item 8.01 Other Events.

On June 12, 2013, purported shareholders of Lufkin Industries, Inc. (the “Company”) filed a lawsuit (the “Action”) in the District Court of Angelina County, Texas challenging the previously disclosed Agreement and Plan of Merger, dated as of April 5, 2013, among General Electric Company (“GE”), Red Acquisition, Inc. (“Merger Sub”) and the Company (the “Merger Agreement”). The Action names John F. Glick, Douglas V. Smith, John F. Anderson, Suzanne V. Baer, John D. Hofmeister, James T. Jongebloed, John H. Lollar, Richard R. Stewart, Howard J. Trout, Jr., Thomas E. Wiener, the Company, GE and Merger Sub as defendants. The Action seeks to enjoin the merger proposed by the Merger Agreement and alleges, among other things, that the members of the Company’s board of directors (the “Board”) breached their fiduciary duties by agreeing to sell the Company for insufficient consideration and reaching that decision through an inadequate process and that GE and Merger Sub aided and abetted the Board in breaching its fiduciary duties.

The Action was brought by one of the two attorneys that submitted a demand letter to the Company in response to the announcement of the Merger Agreement. Receipt of both of the demand letters was disclosed in the Company’s Definitive Proxy Statement filed on May 30, 2013 (the “Proxy Statement”). Also disclosed in the Proxy Statement was the fact that the Board had established a committee (the “Special Committee”), consisting of independent and disinterested directors, to investigate, review and evaluate the allegations raised in the two demand letters and to make recommendations to the Board as to any actions to be taken in response to such allegations. The Special Committee engaged separate counsel that is independent of the Company and GE to assist it with its investigation, review and evaluations. The work of the Special Committee is underway.

The Company and GE are fully prepared to defend the Action and intend to do so vigorously.

The Proxy Statement contains important information about the Company, GE, Merger Sub, the proposed merger and related matters. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE PROXY STATEMENT CAREFULLY.

Investors and security holders are able to obtain free copies of the Proxy Statement and other documents filed with the SEC by the Company through the web site maintained by the SEC at www.sec.gov or by phone, email or written request by contacting the Company at the following:

Address: 601 South Raguet, Lufkin, TX 75904-3951

Phone: (936) 631-2749

Email: cboone@lufkin.com

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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