Note F - Segment Information - Segment Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 31, 2017
Net sales	$ 26,077,710	$ 18,317,506	$ 49,160,979	$ 40,711,270
Interest & other income	(4,375)	(14,750)	(8,750)	(29,500)
Total earnings (loss) before taxes	457,020	(946,790)	686,424	(3,277,778)
Assets	69,369,957		69,369,957		$ 63,263,297
Operating Segments [Member]
Operating profit (loss)	868,000	(531,000)	1,619,000	(2,319,000)
Assets	63,935,000		63,935,000		59,132,000
Operating Segments [Member] | Coil [Member]
Net sales	20,128,000	15,451,000	38,138,000	34,450,000
Operating profit (loss)	552,000	118,000	1,305,000	(1,396,000)
Assets	28,493,000		28,493,000		21,833,000
Operating Segments [Member] | Tubular [Member]
Net sales	5,950,000	2,867,000	11,023,000	6,261,000
Operating profit (loss)	316,000	(649,000)	314,000	(923,000)
Assets	35,442,000		35,442,000		37,299,000
Corporate, Non-Segment [Member]
Corporate expenses	415,000	$ 431,000	942,000	$ 988,000
Assets	$ 5,435,000		$ 5,435,000		$ 4,131,000