Note G - Segment Information - Segment Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2018
Net sales	$ 43,326,080	$ 28,033,521	$ 144,951,427	$ 77,194,500
Interest & other income	(6,275)	(4,375)	(75,325)	(13,125)
Total earnings before taxes	880,867	721,238	8,289,004	1,810,790
Assets	93,859,735		93,859,735		$ 81,653,307
Coil [Member]
Net sales	28,730,992	22,409,571	94,688,636	60,547,245
Tubular [Member]
Net sales	14,595,088	5,623,950	50,262,791	16,647,255
Operating Segments [Member]
Operating profit (loss)	1,394,000	1,180,000	10,195,000	3,203,000
Assets	91,001,000		91,001,000		77,369,000
Operating Segments [Member] | Coil [Member]
Net sales	28,731,000	22,410,000	94,688,000	60,547,000
Operating profit (loss)	744,000	1,233,000	5,847,000	2,942,000
Assets	50,293,000		50,293,000		34,359,000
Operating Segments [Member] | Tubular [Member]
Net sales	14,595,000	5,624,000	50,263,000	16,648,000
Operating profit (loss)	650,000	(53,000)	4,348,000	261,000
Assets	40,708,000		40,708,000		43,010,000
Corporate, Non-Segment [Member]
Corporate expenses	519,000	$ 463,000	1,981,000	$ 1,405,000
Assets	$ 2,859,000		$ 2,859,000		$ 4,284,000