Statements of Consolidated Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Net sales	$ 108,413	$ 99,239	$ 315,467	$ 281,320
Cost of products sold	74,922	65,704	215,255	193,446
GROSS PROFIT	33,491	33,535	100,212	87,874
Costs and expenses
Selling	8,965	8,957	27,297	25,867
General and administrative	11,655	11,042	33,859	32,143
Research and engineering	3,706	3,520	11,013	10,821
Other operating expense - net	1,150	206	2,950	681
Total costs and expenses	25,476	23,725	75,119	69,512
OPERATING INCOME	8,015	9,810	25,093	18,362
Other income (expense)
Interest income	111	62	340	325
Interest expense	(364)	(255)	(992)	(831)
Other income - net	94	122	267	259
Total other income (expense)	(159)	(71)	(385)	(247)
INCOME BEFORE INCOME TAXES	7,856	9,739	24,708	18,115
Income tax (benefit) expense	(1,198)	3,461	3,390	6,163
NET INCOME	$ 9,054	$ 6,278	$ 21,318	$ 11,952
BASIC EARNINGS PER SHARE
Net income	$ 1.80	$ 1.23	$ 4.23	$ 2.34
DILUTED EARNINGS PER SHARE
Net income	1.76	1.23	4.19	2.33
Cash dividends declared per share	$ 0.20	$ 0.20	$ 0.60	$ 0.60
Weighted-average number of shares outstanding - basic	5,025	5,104	5,038	5,113
Weighted-average number of shares outstanding - diluted	5,138	5,120	5,088	5,129