<PAGE>
 
                    U.S. Securities and Exchange Commission
                            Washington, D.C. 20549

                                   FORM 10-Q

[X]  QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE
     ACT OF 1934

               For the Quarterly Period Ended November 30, 1997

[_]  TRANSITION REPORT UNDER SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT
     OF 1934

              For the Transition Period from    N/A    to    N/A
                                               -----        -----

                          Commission File No. 1-7755


                               Summa Industries
               (Name of registrant as specified in its charter)


                 California                         95-1240978
       (State or other jurisdiction of           (I.R.S. Employer
        incorporation or organization)        Identification Number)


       21250 Hawthorne Boulevard, Suite 500, Torrance, California 90503
         (Address of principal executive offices, including Zip Code)


                Registrant's Telephone Number:  (310) 792-7024


Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such report), and (2) has been subject to such filing
requirements for the past 90 days.  Yes  X         No
                                        ---           ---


The number of shares of common stock outstanding as of December 15, 1997 was
4,119,384.
<PAGE>
 
                                Summa Industries



                                     INDEX

<TABLE> 
<CAPTION> 

<S>                                                                         <C> 
PART I - FINANCIAL INFORMATION                                              Page

Item 1. Financial Statements:
 
        Condensed Consolidated Balance Sheets -
        August 31, 1997 and November 30, 1997 (unaudited)...................  3
                                       

        Condensed Consolidated Statements of Income (unaudited) -
        three months ended November 30, 1996 and 1997.......................  4
                   

        Condensed Consolidated Statements of Cash Flows (unaudited) -
        three months ended November 30, 1996 and 1997.......................  5
                   

        Notes to Condensed Consolidated Financial Statements (unaudited)....  6
                   
                   
Item 2. Management's Discussion and Analysis
        of Financial Condition and Results of Operations....................  7
                   
                   
PART II - OTHER INFORMATION.................................................  8
 

Item 1. Legal Proceedings...................................................  8
Item 5. Other Information...................................................  9
Item 6. Exhibits and Reports on Form 8-K.................................... 10
          
 
Signature Page............................................................. 10
</TABLE> 
 
                                       2
<PAGE>
 
                               Summa Industries
                     CONDENSED CONSOLIDATED BALANCE SHEETS

 
<TABLE> 
<CAPTION> 

 
                                           August 31, 1997   November 30, 1997
                                                                    (unaudited)
                                           ---------------   -----------------
<S>                                        <C>               <C>   
ASSETS
Current assets:
 
      Cash                                     $ 2,883,000         $   197,000
 
      Accounts receivable                        7,023,000          12,986,000
 
      Inventories                                3,903,000           9,487,000
 
      Prepaid expenses and other                 1,647,000           2,283,000
                                               -----------         ----------- 
         Total current assets                   15,456,000          24,953,000
 
 
Property, plant and equipment                   20,248,000          25,074,000
 
      Less accumulated depreciation              3,888,000           4,560,000
                                               -----------         -----------
         Net property, plant and equipment      16,360,000          20,514,000
          
Other assets                                     2,331,000           2,155,000
 
Goodwill and other intangibles, net              1,868,000          15,536,000
                                               -----------         -----------
                                               $36,015,000         $63,158,000
                                               ===========         ===========
 
LIABILITIES AND SHAREHOLDERS' EQUITY
 
Current liabilities:
 
      Accounts payable                         $ 2,006,000         $ 5,004,000
 
      Accrued liabilities                        2,673,000           5,381,000
 
      Current maturities of long-term debt       2,673,000           2,101,000
                                               -----------         -----------
         Total current liabilities               7,352,000          12,486,000
 
Long-term debt, net of current maturities        5,571,000          23,913,000
 
Other long term liabilities                      2,127,000           3,295,000
                                               -----------         -----------
         Total liabilities                      15,050,000          39,694,000
 
Shareholders' equity:
 
      Common stock, par value $.001;
        10,000,000 shares authorized, 
        4,099,044 and 4,119,384 shares issued 
        and outstanding at August 31, 1997 
        and November 30, 1997, respectively.    16,226,000          17,705,000
            
      Retained earnings                          4,739,000           5,759,000
                                               -----------         -----------
         Total shareholders' equity             20,965,000          23,464,000
                                               -----------         -----------
                                               $36,015,000         $63,158,000
                                               ===========         ===========
</TABLE> 
 
 
                            See accompanying notes.

                                       3
<PAGE>
 
                               Summa Industries
                  CONDENSED CONSOLIDATED STATEMENTS OF INCOME
                                  (unaudited)
<TABLE> 
<CAPTION> 
 
                                                    Three months ended
                                            ------------------------------------
                                            November 30, 1996  November 30, 1997
                                            -----------------  -----------------
<S>                                         <C>                <C>

Net sales                                          $3,139,000        $17,435,000

Cost of sales                                       1,656,000         11,902,000
                                            -----------------  -----------------
Gross profit                                        1,483,000          5,533,000

Selling, general and administrative
 and other expenses                                 1,151,000          3,590,000
                                            -----------------  -----------------
Operating income                                      332,000          1,943,000

Interest expense (income), net                        (28,000)           201,000
                                            -----------------  -----------------
Income before provision for taxes                     360,000          1,742,000

Provision for income taxes                            147,000            722,000

Net income                                         $  213,000        $ 1,020,000


Net income per common and equivalent share         $      .13        $       .23
                                            =================  =================
Weighted average shares outstanding                 1,666,000          4,369,000
                                            =================  =================
</TABLE> 


                            See accompanying notes.

                                       4
<PAGE>
 
                               Summa Industries
                  CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
                                  (unaudited)
<TABLE> 
<CAPTION> 

 
                                                                          Three months ended
                                                                  ------------------------------------
                                                                  November 30, 1996  November 30, 1997
                                                                  -----------------  -----------------
<S>                                                               <C>                <C>
Operating activities:                                             
Net income                                                              $   213,000      $  1,020,000
                                                                  -----------------  ----------------
Adjustments to reconcile net income to net cash provided by       
  (used in) operating activities:                                 
                                                                  
  Depreciation and amortization                                             164,000           766,000
  Loss on disposition of property, plant and equipment                          ---           120,000
  Net change in assets and liabilities                            
    Accounts receivable                                                     (43,000)         (982,000)
    Inventories                                                              11,000           151,000
    Prepaid expenses and other                                               28,000          (167,000)
    Accounts payable                                                       (298,000)          466,000
    Accrued liabilities                                                    (303,000)          367,000
                                                                  -----------------  ----------------
Total adjustments                                                          (441,000)          721,000
                                                                  -----------------  ----------------
       Net cash provided by (used in) operating activities                 (228,000)        1,741,000
                                                                  -----------------  ----------------
Investing activities:                                             
    Purchase of business (Note 3)                                          (227,000)      (21,626,000)
    Property, plant & equipment                                                 ---          (547,000)
    Net decrease in unexpended revenue bond proceeds                            ---           371,000
                                                                  -----------------  ----------------
       Net cash used in investing activities                               (227,000)      (21,802,000)
                                                                  -----------------  ----------------
Financing activities:                                             
    Net proceeds from line of credit                                         32,000               ---
    Proceeds from issuance of long-term debt                                    ---        24,637,000
    Payments of long-term debt                                                  ---        (8,696,000)
    Proceeds from exercise of stock options                                     ---           134,000
    Cash acquired in acquisition of businesses, net of cash paid            369,000         1,300,000
                                                                  -----------------  ----------------
       Net cash provided by financing activities                            401,000        17,375,000
                                                                  -----------------  ----------------
Net decrease in cash                                                        (54,000)       (2,686,000)
Cash at beginning of period                                                 567,000         2,883,000
                                                                  -----------------  ----------------
Cash at end of period                                                   $   513,000      $    197,000
                                                                  =================  ================
Supplemental cash flow information:                               
  Cash paid during the period for:                                
       Interest                                                         $     7,000      $    149,000
                                                                  =================  ================
       Income tax                                                       $   263,000      $    375,000
                                                                  =================  ================
Non-cash investing and financing activities                       
       Common stock issued and value assigned to stock options    
         for acquisitions (Note 3)                                      $ 9,941,000      $  1,345,000
                                                                  =================  ================
Details of acquisition (Note 3):                                  
       Fair value of assets acquired                                    $23,910,000      $ 31,192,000
       Liabilities assumed or incurred                                   13,825,000         8,221,000
       Common stock issued and value assigned to stock options            9,941,000         1,345,000
                                                                  -----------------   --------------- 
       Cash paid                                                            144,000        21,626,000
       Less cash acquired                                                  (513,000)       (1,300,000)
                                                                  -----------------   --------------- 
       Net cash (acquired) used in acquisition                          $  (369,000)     $ 20,326,000
                                                                  -----------------   --------------- 
</TABLE> 
 
                            See accompanying notes.

                                       5
<PAGE>
 
                                Summa Industries


              NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
                                        
1.   Basis of presentation

     The accompanying condensed consolidated financial statements of Summa
     Industries (the "Company"), some of which are unaudited, have been
     condensed in certain respects and should, therefor, be read in conjunction
     with the audited financial statements and notes related thereto contained
     in the Company's Annual Report on Form 10-K for the year ended August 31,
     1997. In the opinion of the Company, the accompanying unaudited interim
     consolidated financial statements contain all adjustments (all of which are
     of a normal recurring nature) necessary for a fair presentation for the
     interim period. (See Note 3 below.) The results of operations for the three
     months ended November 30, 1997 are not necessarily indicative of the
     results to be expected for the full year ending August 31, 1998.

2.   Inventories

     Inventories at August 31, 1997 and November 30, 1997 were as follows:
<TABLE>
<CAPTION>
 
                                August 31, 1997   November 30, 1997
                                                        (unaudited)
                                ---------------   -----------------
        <S>                     <C>               <C>
        Finished goods               $1,557,000          $4,213,000
 
        Work in process                 108,000             172,000
 
        Material and parts            2,238,000           5,102,000
                                ---------------   -----------------
                                     $3,903,000          $9,487,000
                                ===============   =================
</TABLE>

3.   Acquisitions

     On October 28, 1997, the Company completed the acquisition of Calnetics
     Corporation ("Calnetics").  The total acquisition cost was $31,192,000,
     consisting of cash due to former Calnetics shareholders of $22,335,000,
     acquisition costs estimated to be $80,000, liabilities assumed or incurred
     of $7,432,000 and an assigned value of $1,345,000 for options issued in
     conjunction with the transaction, primarily replacement options issued to
     Calnetics employees who continued with the Company.  The acquisition has
     been accounted for using the purchase method of accounting and,
     accordingly, the purchase price has been allocated to identifiable tangible
     and intangible assets purchased and liabilities assumed or incurred based
     upon their fair value at the date of acquisition.  The excess of the
     purchase price over the fair values of the net assets acquired amounted to
     $13,721,000 and has been recorded as goodwill which will be amortized on a
     straight-line basis over 30 years.

     As a consequence of the acquisition, the consolidated balance sheet of the
     Company at November 30, 1997 includes the balance sheet of Calnetics along
     with the preliminary purchase accounting adjustments.  The results of one
     month of operations of Calnetics have been included in the consolidated
     results of operations and the consolidated statement of cash flows of the
     Company for the quarter ended November 30, 1997.

     Neither the results of operations of LexaLite International Corporation,
     acquired on November 22, 1996, nor those of Calnetics are included in the
     consolidated results of operations of the Company for the quarter ended
     November 30, 1996.  The following proforma information presents results of
     operations of the Company with LexaLite and Calnetics as though the
     acquisition of LexaLite had been made as of September 1, 1996 and as though
     the acquisition of Calnetics had been made as of September 1, 1996 and
     1997, respectively.  Proforma adjustments have been made to give effect to
     the amortization of goodwill and other intangibles, adjustments in
     depreciation and inventory value, a reduction in redundant operating
     expense, interest expense related to

                                       6
<PAGE>
 
     acquisition debt, the related tax effects and the effect upon earnings per
     share of the additional shares of stock given in exchange for LexaLite
     stock and of stock options issued in conjunction with the acquisitions.

<TABLE>
<CAPTION>
                                                      Three months ended
                                            ------------------------------------
                                            November 30, 1996  November 30, 1997
                                            -----------------  -----------------
<S>                                         <C>                <C>
Net sales                                         $20,192,000        $23,153,000
Net income                                            553,000          1,128,000
                                            =================  =================
Net income per common and equivalent share        $       .13        $       .25
 
</TABLE>

MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF
OPERATIONS

Statements contained in this Quarterly Report on Form 10-Q that are not purely
historical are forward-looking statements within the meaning of Section 27A of
the Securities Act of 1933 and Section 21E of the Securities Exchange Act of
1934, including but not limited to statements regarding Summa's expectations,
hopes, beliefs, intentions or strategies regarding the future.  Actual results
could differ materially from those projected in any forward-looking statements
as a result of a number of factors, including those detailed in this
"Management's Discussion and Analysis" section and elsewhere herein and in the
Company's Annual Report on Form 10-K for the fiscal year ended August 31, 1997.
The forward-looking statements are made as of the date hereof, and the Company
assumes no obligation to update the forward-looking statements, or to update the
reasons why actual results could differ materially from those projected in the
forward-looking statements.

Liquidity and Capital Resources
-------------------------------

The Company's working capital at November 30, 1997 was $12,467,000 compared to
$8,104,000 at August 31, 1997.  The primary reason for the increase was the
inclusion of the balance sheet of newly acquired Calnetics.

In connection with the acquisition of Calnetics, the Company entered into new
credit facilities consisting of $13,500,000 in term debt, a three year revolving
line of credit of up to $15,000,000 depending upon the amount of eligible
accounts receivable and inventory and a $5,000,000 acquisition facility.

At November 30, 1997, the balance on the term loan was $13,500,000 and the
balance on the line of credit was  $6,830,000 with about $7,498,000 additional
availability on the line of credit.  None of the $5,000,000 acquisition facility
was in use.  At November 30, 1997, the Company had used $21,626,000 for the
purchase of Calnetics shares and has an obligation to acquire the remaining
outstanding Calnetics shares for an aggregate of $709,000.  Interest is due
monthly on both facilities at a base rate plus an applicable margin.  At
November 30, 1997, based upon the base rate optionally selected, Summa's debt
incurred in connection with the acquisition of Calnetics bears interest at less
than the prime rate. Additionally, the Company has an aggregate of $5,684,000 in
long term bonds, mortgages and sub-ordinated debt, with an average interest rate
less than the prime rate.

Substantially all of Summa's assets are pledged to secure the debt described
above.  The term debt and revolving line of credit are subject to various bank
covenants.

The Company believes that cash flows from operations and available lines of
credit will be sufficient to fund working capital and planned capital
expenditures for the next twelve months.

The Company has a strategy of growth by acquisition.  Although there are no
plans to make a specific acquisition for cash, in the event such a plan were
adopted, which required funds exceeding the availability described above,
an alternate source of funds to accomplish the acquisition would have to be
developed.  The Company has 10,000,000 

                                       7
<PAGE>
 
shares of common stock authorized, of which 4,119,384 shares were outstanding at
November 30, 1997 and 5,000,000 shares of "blank check" preferred stock
authorized of which none is outstanding. The Company could issue additional
shares of common or preferred stock to raise funds.

Results of Operations
---------------------

The following table sets forth certain statement of income information for
Summa's continuing operations as a percent of sales for the fiscal quarters
ended November 30.
<TABLE>
<CAPTION>
 
                                  1996      1997
                                 ------    ------
  <S>                            <C>       <C>

  Sales                          100.0%    100.0% 
 
  Gross profit                    47.2%     31.7%
 
  S,G & A and other expense       36.7%     20.6%
 
  Operating income                10.6%     11.1%
 
  Interest expense (income)       (0.9%)     1.1%
 
  Income before taxes             11.5%     10.0%
 
  Net income                       6.8%      5.9%
                                 ======    ======
  Effective tax rate              40.8%     41.4%
</TABLE>

Sales for the first quarter ended November 30, 1997 increased $14,296,000 or
455% compared to the same period in the prior year, due primarily to the
inclusion of the sales of LexaLite for the full quarter and the inclusion of the
sales of subsidiaries of Calnetics for one month of the quarter, neither of
which were included in the prior year first quarter.  Additionally, sales of the
material handling components business continued to grow.

Consolidated gross profit increased $4,050,000 or 273% primarily due to the
inclusion of the recently acquired businesses.  As a percentage of sales, gross
profit decreased from 47.2% for the quarter ended November 30, 1996 to 31.7% for
the quarter ended November 30, 1997, primarily due to the inclusion of the sales
of the recently acquired businesses at typically lower gross margins than those
of Summa's previous business.  Additionally, the quarter ended November 30, 1997
included a one-time $330,000 charge representing 1.9% of sales for the fair
value adjustment for inventory made in the purchase accounting for Calnetics.

Operating expenses increased $2,439,000, or 212% from the comparable prior year
period, but as a percentage of sales, decreased from 36.7% to 20.6% primarily
because of the inclusion of the recently acquired businesses which operate with
lower operating expenses as a percentage of sales.  Net interest expense
incurred in the current period related to interest expense on debt acquired with
the acquisition of LexaLite and interest on debt incurred in connection with the
acquisition of Calnetics.  The change in the effective tax rate from 40.8% in
the prior year period to 41.4% in the current period is primarily associated
with the non-deductible amortization of goodwill related to the recent
acquisitions offset somewhat by a lower effective combined state income tax
rate.

The Company's backlog, believed to be firm, increased from $6,323,000 at August
31, 1997 to $8,707,000 at November 30, 1997, primarily as a result of the
backlog of newly acquired Calnetics.  The Company's order backlog is not a
significant indicator of future sales volumes.

PART II - OTHER INFORMATION

Item 1.  Legal Proceedings
--------------------------

The Company encounters lawsuits from time to time in the ordinary course of
business, and at November 30, 1997, the Company or its affiliates were parties
to two civil lawsuits as described below.  Although the Company has obtained
liability insurance coverage for each of the past five years, such insurance may
not be available in the future at economically feasible premium rates.
Additionally, some lawsuits filed against the Company in the past have contained

                                       8
<PAGE>
 
claims not covered by insurance, or have sought damages in excess of policy
limits, and such claims could be filed in the future.  Any losses that the
Company may suffer from current or future lawsuits, and the effect such
litigation may have upon the reputation and marketability of the Company's
products, could have a material adverse impact on the financial condition and
prospects of the Company.

Laitram, et al. v. KVP Systems, Inc., et al. was filed in the U.S. District
--------------------------------------------
Court in Eastern Louisiana in September 1993.  The plaintiffs claim KVP has
infringed upon two patents.  The venue was changed to the Federal District Court
in Sacramento, California.  KVP contended the claims were invalid and filed
certain counterclaims.  On April 24, 1997, the District Court ruled that KVP's
products do not infringe plaintiff's patents and also dismissed the
counterclaims.  Both parties have appealed the ruling.  Although the Company
believes it has a reasonable expectation of prevailing on appeal, in the absence
of applicable insurance, the consequences of an adverse determination would be
borne by the Company.

In Wright v. Stang, et al., a piece of pipe, to which a water cannon
   ------------------------
manufactured by Stang was attached, broke, knocking a fireman down.  Since Stang
did not make or supply the pipe which failed, the case was dismissed.
Subsequently, the dismissal was reversed on appeal.  The Company has $2,000,000
in product liability insurance applicable in this case.

Item 2.  Changes in Securities
------------------------------

None.

Item 3.  Default upon Senior Securities
---------------------------------------

None.

Item 4.  Submission of Matters to a Vote of Security Holders
------------------------------------------------------------

None.

Item 5.  Other Information
--------------------------

On October 28, 1997, the Company acquired all of the outstanding capital stock
of Calnetics through a merger of a newly formed and wholly-owned subsidiary of
the Company with and into Calnetics.  (See Note 3 to Notes to Condensed
Consolidated Financial Statements above for additional information.)  In this
acquisition, the Company also acquired the following operating subsidiaries of
Calnetics: Manchester Plastics Co., Inc., a California corporation which
manufactures proprietary and other  products of acrylic, polycarbonate and
polystyrene  sheet, principally for the building materials and industrial
industries; Ny-Glass Plastics, Inc., a California corporation which manufactures
plastic parts, principally by injection molding and structural foam molding, and
performs certain value-added services for customers in a variety of industries;
and Agricultural Products, Inc., a California corporation which manufactures
plastic fittings, filters, tubing and accessories, principally for use in
agricultural irrigation.

Prior to October 1986, a previously owned business unit of one of the Company's
subsidiaries operated a facility on property within an area subsequently
designated as a federal Superfund site.  The Company learned that hazardous
substances have been identified in the subsurface of the property and that the
current owner has been requested by a state agency to undertake additional
investigation at the property.  The Company is also aware that the property has
been subject to a general notice letter issued by the United States
Environmental Protection Agency under the federal Superfund law.  The Company,
as the successor to one of several prior operators of the property, may be held
responsible for the contamination at the site regardless of whether its
subsidiary caused the contamination.  The Company does not believe it is
responsible for any contamination at the property, and has not been notified or
contacted by any governmental authority in that regard, nor named in any
proceeding relating to the property.  However, if the Company were held liable
under federal Superfund law, or other environmental law, or had to defend itself
against such a claim, the consequences could be material to future results of
operations of the Company, but would not be expected to have a material effect
on its financial condition.

The Company is in the process of an Internal Revenue Service ("IRS")
examination regarding the tax exempt status of

                                       9
<PAGE>
 
one of its industrial revenue bonds. The IRS has informed the Company that
preliminary findings indicate that the bond may not be tax exempt and thus the
Company may be required to pay additional interest and/or taxes. If it is
determined that the bond is not tax exempt, the consequences could be material
to future results of operations of the Company, but would not be expected to
have a material effect on its financial condition.

Item 6.  Exhibits and Reports on Form 8-K
-----------------------------------------

          (a)  Exhibits.
               ---------

               27.1    Financial Data Schedule

               In addition, each of the exhibits previously filed with the
Commission in connection with (i) the Company's Annual Report on Form 10-K for
the fiscal year ended August 31, 1997 (File No. 1-7755), (ii) the Company's
Registration Statement on Form S-4 (File No. 333-11571), and (iii) the
Calnetics' Annual Report on Form 10-K for the fiscal year ended June 30, 1997
(File No. 0-08767), as well as Appendix I to the Calnetics' definitive Proxy
Statement on Schedule 14A (File No. 0-08767) for the Special Meeting of
Shareholders held October 28, 1997, are incorporated herein.

          (b)  Current Reports on Form 8-K.
               ----------------------------

               None.


                                  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 thereunto duly authorized on December 31, 1997.

                          Summa Industries

                          /s/ James R. Swartwout
                          ----------------------
                          James R. Swartwout, President and Chief Financial
                          Officer

                          /s/ Trygve M. Thoresen
                          ----------------------
                          Trygve M. Thoresen, Vice President and Secretary

                                       10