<ARTICLE> 5
       
                                                                                            
<PERIOD-TYPE>                   3-MOS                   6-MOS                   9-MOS                   YEAR
<FISCAL-YEAR-END>                     DEC-31-1997             DEC-31-1997             DEC-31-1997             DEC-31-1997
<PERIOD-END>                          MAR-31-1997             JUN-30-1997             SEP-30-1997             DEC-31-1997
<CASH>                                      7,555                   7,186                  29,726                  21,469
<SECURITIES>                                    0                       0                       0                       0
<RECEIVABLES>                              58,287                  53,722                  53,937                  57,438
<ALLOWANCES>                                1,059                   1,072                   1,454                   1,705
<INVENTORY>                                67,920                  67,452                  93,261                  91,733
<CURRENT-ASSETS>                          146,005                 139,494                 189,056                 184,654
<PP&E>                                    323,421                 329,147                 373,936                 369,469
<DEPRECIATION>                            114,806                 120,439                 126,727                 132,127
<TOTAL-ASSETS>                            400,517                 393,139                 537,181                 552,426
<CURRENT-LIABILITIES>                      65,119                  61,599                  69,280                  67,911
<BONDS>                                    73,483                  62,865                 187,503                 194,325
<PREFERRED-MANDATORY>                           0                       0                       0                       0
<PREFERRED>                                     0                       0                       0                       0
<COMMON>                                    1,277                   1,279                   1,293                   1,295
<OTHER-SE>                                219,461                 224,828                 233,617                 224,659
<TOTAL-LIABILITY-AND-EQUITY>              400,517                 393,139                 537,181                 552,426
<SALES>                                    90,858                 189,120                 269,830                 371,277
<TOTAL-REVENUES>                           91,894                 190,613                 271,978                 374,215
<CGS>                                      64,155                 132,804                 189,611                 260,253
<TOTAL-COSTS>                              64,155                 132,804                 189,611                 260,253
<OTHER-EXPENSES>                                0                       0                       0                       0
<LOSS-PROVISION>                                0                       0                       0                       0
<INTEREST-EXPENSE>                          1,157                   2,303                   3,078                   5,330
<INCOME-PRETAX>                            10,953                  23,970                  34,996                  32,607
<INCOME-TAX>                                3,505                   7,670                  11,165                  14,831
<INCOME-CONTINUING>                         7,448                  16,300                  23,831                  17,776
<DISCONTINUED>                                  0                       0                       0                       0
<EXTRAORDINARY>                                 0                       0                       0                       0
<CHANGES>                                       0                       0                       0                       0
<NET-INCOME>                                7,448                  16,300                  23,831                  17,776
<EPS-PRIMARY>                                0.63<F1>                1.39<F1>                2.02<F1>                1.50<F1>
<EPS-DILUTED>                                0.62                    1.36                    1.97                    1.46
<FN>
<F1>The amount is reported as EPS-BASIC AND NOT FOR EPS-PRIMARY.
</FN>