As filed with the Securities and Exchange Commission on January 14, 1998

==============================================================================


                    SECURITIES AND EXCHANGE COMMISSION
                          Washington, D.C.  20549

                               ------------

                              SCHEDULE 14D-1
                             (Amendment No. 4)

            TENDER OFFER STATEMENT PURSUANT TO SECTION 14(d)(1)
                  OF THE SECURITIES EXCHANGE ACT OF 1934

                               ------------

                            TRIMAS CORPORATION

                      (Exact name of Subject Company)

                              MASCOTECH, INC.
                        MASCOTECH ACQUISITION, INC.

                                 (Bidders)

                               ------------

                       Common Stock, $.01 Par Value
                      (Title of Class of Securities)

                               ------------

                                 896215100
                   (CUSIP Number of Class of Securities)

                               ------------

                           David B. Liner, Esq.
                              MascoTech, Inc.
                            21001 Van Born Road
                          Taylor, Michigan 48180
                              (313) 274-7405
(Name, Address and Telephone Number of Persons Authorized to Receive Notices
        and Communications on Behalf of Person(s) Filing Statement)

                               ------------

                              With Copies to:

        David W. Ferguson, Esq.              Jerome M. Schwartz, Esq.
         Davis Polk & Wardwell                 Dickinson Wright PLLC
          450 Lexington Avenue            500 Woodward Avenue, Suite 4000
        New York, New York 10017              Detroit, Michigan 48226
             (212) 450-4000                       (313) 223-3628


==============================================================================



               This Amendment No. 4 (this "Amendment") amends and supplements
the Tender Offer Statement on Schedule 14D-1 (the "Schedule 14D-1") originally
filed on December 17, 1997 by MascoTech, Inc., a Delaware corporation
("Parent"), and MascoTech Acquisition, Inc., a Delaware corporation and a
wholly owned subsidiary of Parent ("Purchaser"), as amended by Amendment No.
1, dated December 22, 1997, Amendment No. 2, dated December 31, 1997 and
Amendment No. 3, dated January 7, 1998, relating to the offer by Purchaser to
purchase all of the issued and outstanding shares (the "Shares") of common
stock, $.01 par value per share, of TriMas Corporation, a Delaware
corporation, at a price of $34.50 per Share, net to the seller in cash, upon
the terms and subject to the conditions set forth in the Offer to Purchase
dated December 17, 1997 and in the related Letter of Transmittal.

               All capitalized terms used in this Amendment without definition
have the meanings attributed to them in the Schedule 14D-1.

               The item of the Schedule 14D-1 set forth below is hereby
amended and supplemented as follows:

Item 11.   Material to be Filed as Exhibits.

               Item 11 is hereby supplemented and amended by adding the
following exhibit:

               (c)(11) Amendment No. 2 dated as of January 13, 1998 to the
                       Agreement and Plan of Merger dated as of December
                       10, 1997 as amended by Amendment No. 1 dated as of
                       December 15, 1997 among the Company, Parent and
                       Purchaser.


                                 SIGNATURE

               After due inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this Amendment is true, complete and
correct.

January 14, 1998                   MASCOTECH, INC.


                                   By: /s/ David B. Liner
                                       ------------------------------------
                                       Name:  David B. Liner
                                       Title: Vice President and Corporate
                                              Counsel


                                   MASCOTECH ACQUISITION, INC.


                                   By: /s/ David B. Liner
                                       ------------------------------------
                                       Name:  David B. Liner
                                       Title: Secretary



                               EXHIBIT INDEX

Exhibit No.
- -----------
(c)(11)        Amendment No. 2 dated as of January 13, 1998 to the Agreement
               and Plan of Merger dated as of December 10, 1997 as amended
               by Amendment No. 1 dated as of December 15, 1997 among the
               Company, Parent and Purchaser.


                                                               Exhibit (c)(11)

              AMENDMENT NO. 2 TO AGREEMENT AND PLAN OF MERGER

               AMENDMENT NO. 2 dated as of January 13, 1998 to the Agreement
and Plan of Merger dated as of December 10, 1997 as amended by Amendment No. 1
dated as of December 15, 1997 (the "Agreement") among TriMas Corporation, a
Delaware corporation (the "Company"), MascoTech, Inc., a Delaware corporation
("Buyer"), and MascoTech Acquisition, Inc., a Delaware corporation and a
wholly owned subsidiary of Buyer ("Merger Sub").

               WHEREAS, the parties hereto desire to amend the Agreement as
set forth below to effectuate the transfer of the Shares owned by Buyer to
Merger Sub.

               NOW, THEREFORE, the parties hereto agree as follows:

               Section 1.01. Defined Terms; References.  Unless otherwise
specifically defined herein, each term used herein which is defined in the
Agreement has the meaning assigned to such term in the Agreement. Each
reference to "hereof", "hereunder", "herein" and "hereby" and each other
similar reference and each reference to "this Agreement" and each other
similar reference contained in the  Agreement shall, after this Amendment
becomes effective, refer to the Agreement as amended hereby.

               Section 1.02. Amendment of Section 5.01 of the Agreement.  The
last sentence of Section 5.01 of the Agreement is hereby replaced and amended
in its entirety to read in full as follows:

                  Since the date of its incorporation, Merger Sub has not
                  engaged in any activities other than in connection with or
                  as contemplated by this Agreement or in connection with
                  arranging any financing required to consummate the
                  transactions contemplated hereby and except that it is
                  contemplated that immediately prior to the Effective Time,
                  NI Industries, Inc., a Delaware corporation and a wholly
                  owned subsidiary of Buyer ("NI Industries"), shall be merged
                  with and into Merger Sub in accordance with the Delaware
                  Law, whereupon the separate existence of NI Industries shall
                  cease, and Merger Sub shall be the surviving corporation.

               Section 1.03.  Amendment of Section 11.12 of the Agreement.
Section 11.12 of the Agreement shall be amended to include NI Industries as a
term defined in Section 5.01 of the Agreement.

               Section 1.04.  Representations of Each Party.  Each party
represents and warrants that (i) the execution, delivery and performance of
this Amendment by such party have been duly authorized by all necessary
corporate action (including, in the case of the Company, the approval of the
Company Special Committee) and (ii) this Amendment constitutes a valid and
binding agreement of such party.

               Section 1.05.  Governing Law.  This Amendment shall be
construed in accordance with and governed by the laws of the State of
Delaware.

               Section 1.06.  Counterparts;  Effectiveness.  This Amendment
may be signed in any number of counterparts, each of which shall be an
original, with the same effect as if the signatures thereto and hereto were
upon the same instrument.  This Amendment shall become effective when each
party hereto shall have received counterparts hereof signed by all of the
other parties hereto.

      IN WITNESS WHEREOF, the parties hereto have caused this Amendment No.
2 to be duly executed by their respective authorized officers as of the day
and year first above written.


                                   TRIMAS CORPORATION



                                   By: /s/ Peter C. DeChants
                                       ----------------------------------
                                       Name: Peter C. DeChants
                                       Title: Vice President - Treasurer


                                   MASCOTECH, INC.



                                   By: /s/ Timothy Wadhams
                                       ----------------------------------
                                       Name: Timothy Wadhams
                                       Title: Vice President


                                   MASCOTECH ACQUISITION, INC.



                                   By: /s/ Timothy Wadhams
                                       ----------------------------------
                                       Name: Timothy Wadhams
                                       Title: Vice President and Treasurer