EXHIBIT 5.1

                                   KADANT INC.
                           ONE ACTON PLACE, SUITE 202
                           ACTON, MASSACHUSETTS 01720


                                                                    May 10, 2001


Ladies and Gentlemen:

         I am General Counsel of Kadant Inc., a Delaware corporation (the
"Registrant"), and am issuing this opinion in connection with the Registration
Statement on Form S-3 (the "Registration Statement") being filed by the
Registrant with the Securities and Exchange Commission (the "Commission") for
the purpose of registering with the Commission under the Securities Act of 1933,
as amended (the "Securities Act"), the following Registrant securities:

         (i)   common stock, $0.01 par value per share (the "Common Stock"); and

         (ii)  warrants to purchase Common Stock (the "Warrants");

all of which may be issued from time to time on a delayed or continuous basis
pursuant to Rule 415 under the Securities Act at an aggregate initial offering
price not to exceed $40,000,000.

         Warrants will be issued pursuant to a Warrant Agreement between the
Registrant and a bank or trust company as Warrant Agent.

         I have examined the Registration Statement, including the exhibits
thereto, and such other documents, corporate records and instruments, and have
examined such laws and regulations, as I have deemed necessary for purposes of
rendering the opinions set forth herein. Based upon such examination, I am of
the following opinion:

1.       With respect to the Common Stock, when (i) specifically authorized for
         issuance by the Registrant's Board of Directors or an authorized
         committee thereof (the "Authorizing Votes"), (ii) the Registration
         Statement has become effective under the Securities Act, (iii) the
         terms of the sale of the Common Stock have been duly established in
         conformity with the Registrant's Certificate of Incorporation and
         By-laws and do not violate any applicable law or result in a default
         under or breach of any agreement or instrument binding on the
         Registrant and comply with any requirement or restriction imposed by
         any court or governmental body having jurisdiction over the Registrant,
         (iv) the Common Stock has been issued and sold as contemplated by the
         Registration Statement, and (v) the Registrant has received the
         consideration provided for in the Authorizing Votes, the Common Stock
         will be validly issued, fully paid and non-assessable.

2.       With respect to the Warrants, when (i) specifically authorized for
         issuance by the Authorizing Votes, (ii) the Registration Statement has
         become effective under the Securities Act, (iii) the Warrant Agreement
         relating to the Warrants has been duly authorized, executed and
         delivered, (iv) the terms of the Warrants and of their issuance and
         sale have been duly established in conformity with the Warrant
         Agreement and do not violate any applicable law or result in a default
         under or breach of any agreement or instrument binding upon the
         Registrant and comply with any requirement or restriction imposed by
         any court or governmental body having jurisdiction over the Registrant,
         (v) the Warrants have been duly executed and countersigned in
         accordance with the Warrant Agreement and issued and sold as
         contemplated by the Registration Statement, and (vi) the Registrant has
         received the consideration provided for in the Authorizing Votes, the
         Warrants will constitute valid and legally binding obligations of the
         Registrant, subject to bankruptcy,




         insolvency, fraudulent transfer, reorganization, moratorium and similar
         laws of general applicability relating to or affecting creditors'
         rights and to general equity principles.

         In connection with my examination of the documents indicated above, I
have assumed the genuineness of all signatures, the legal capacity of natural
persons, the authenticity of all documents submitted to me as originals, the
conformity to original documents of all documents submitted to me as certified,
conformed or photostatic copies and the authenticity of the originals of such
copies. As to any facts material to the opinions expressed herein that I have
not independently established or verified, I have relied upon statements and
representations of officers and other representatives of the Registrant and
others.

         I express no opinion herein as to the laws of any state or jurisdiction
other than the state laws of the Commonwealth of Massachusetts, the General
Corporation Law of the State of Delaware and the federal laws of the United
States of America.

         It is understood that this opinion is to be used only in connection
with the offer and sale of the Common Stock and Warrants while the Registration
Statement is in effect.

         This opinion is furnished by me, as counsel to the Registrant, in
connection with the filing of the Registration Statement and, except as provided
in the immediately preceding paragraph, is not to be used, circulated, quoted
for any other purpose or otherwise referred to or relied upon by any other
person without the express written permission of the Registrant.

         I hereby consent to the filing of this opinion as an exhibit to the
Registration Statement. In giving such consent, I do not thereby admit that I am
in the category of persons whose consent is required under Section 7 of the
Securities Act or the rules and regulations of the Commission promulgated
thereunder.


                                                 Very truly yours,

                                                 /s/ Sandra L. Lambert
                                                 -------------------------------
                                                 Sandra L. Lambert
                                                 Vice President, General Counsel