Note G - Segment Information - Segment Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Total Net Sales	$ 53,432,029	$ 26,077,710	$ 101,625,347	$ 49,160,979
Interest & other income	(6,275)	(4,375)	(69,050)	(8,750)
Total earnings before taxes	2,645,625	580,261	7,408,138	1,089,552
Assets	90,720,692		90,720,692		$ 81,653,307
Coil [Member]
Total Net Sales	34,828,444	20,127,839	65,957,644	38,137,674
Tubular [Member]
Total Net Sales	18,603,585	5,949,871	35,667,703	11,023,305
Operating Segments [Member]
Operating profit (loss)	3,301,000	991,000	8,801,000	2,023,000
Assets	86,772,000		86,772,000		77,369,000
Operating Segments [Member] | Coil [Member]
Total Net Sales	34,828,000	20,128,000	65,957,000	38,138,000
Operating profit (loss)	1,925,000	675,000	5,103,000	1,709,000
Assets	43,535,000		43,535,000		34,359,000
Operating Segments [Member] | Tubular [Member]
Total Net Sales	18,604,000	5,950,000	35,668,000	11,023,000
Operating profit (loss)	1,376,000	316,000	3,698,000	314,000
Assets	43,237,000		43,237,000		43,010,000
Corporate, Non-Segment [Member]
Corporate expenses	661,000	$ 415,000	1,462,000	$ 942,000
Assets	$ 3,949,000		$ 3,949,000		$ 4,284,000