Statements of Consolidated Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net sales	$ 108,915	$ 97,512	$ 207,054	$ 182,081
Cost of products sold	73,712	67,839	140,333	127,743
GROSS PROFIT	35,203	29,673	66,721	54,338
Costs and expenses
Selling	9,471	8,626	18,332	16,910
General and administrative	11,288	10,772	22,203	21,101
Research and engineering	3,646	3,612	7,307	7,301
Other operating expense - net	1,465	369	1,800	474
Total costs and expenses	25,870	23,379	49,642	45,786
OPERATING INCOME	9,333	6,294	17,079	8,552
Other income (expense)
Interest income	134	160	229	264
Interest expense	(348)	(277)	(628)	(577)
Other income - net	105	81	173	137
Total other income (expense)	(109)	(36)	(226)	(176)
INCOME BEFORE INCOME TAXES	9,224	6,258	16,853	8,376
Income taxes	2,489	2,102	4,590	2,702
NET INCOME	$ 6,735	$ 4,156	$ 12,263	$ 5,674
BASIC EARNINGS PER SHARE
Net income	$ 1.34	$ 0.81	$ 2.43	$ 1.11
DILUTED EARNINGS PER SHARE
Net income	1.33	0.81	2.42	1.11
Cash dividends declared per share	$ 0.20	$ 0.20	$ 0.40	$ 0.40
Weighted-average number of shares outstanding - basic	5,044	5,116	5,045	5,117
Weighted-average number of shares outstanding - diluted	5,064	5,127	5,064	5,132