Note G - Segment Information - Segment Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017
Net sales	$ 28,033,521	$ 15,988,745	$ 77,194,500	$ 56,700,015
Interest & other income	(4,375)	(14,755)	(13,125)	(44,255)
Total earnings (loss) before taxes	665,838	(370,979)	1,352,262	(3,648,757)
Assets	71,946,823		71,946,823		$ 63,263,297
Operating Segments [Member]
Operating profit (loss)	1,125,000	101,000	2,744,000	(2,218,000)
Assets	68,271,000		68,271,000		59,132,000
Operating Segments [Member] | Coil [Member]
Net sales	22,410,000	13,495,000	60,547,000	47,945,000
Operating profit (loss)	1,178,000	538,000	2,483,000	(858,000)
Assets	26,770,000		26,770,000		21,833,000
Operating Segments [Member] | Tubular [Member]
Net sales	5,624,000	2,494,000	16,648,000	8,755,000
Operating profit (loss)	(53,000)	(437,000)	261,000	(1,360,000)
Assets	41,501,000		41,501,000		37,299,000
Corporate, Non-Segment [Member]
Corporate expenses	463,000	$ 487,000	1,405,000	$ 1,475,000
Assets	$ 3,676,000		$ 3,676,000		$ 4,131,000