Note J - Segment Information - Segment Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2020
Revenue from Contract with Customer, Including Assessed Tax	$ 28,502,049	$ 28,150,817	$ 76,888,329	$ 109,121,717
Operating profit (loss)	2,764,558	(1,149,923)	1,306,559	(2,923,486)
Corporate expenses	736,000	587,000	2,188,000	1,826,000
Interest expense	6,148	2,463	18,356	2,463
Interest and other income	(4,339)	(4,370)	(12,987)	(15,075)
Total earnings (loss) before taxes	2,768,897	(1,145,553)	1,319,546	(2,908,411)
Segment assets	79,369,221		79,369,221		$ 77,344,088
Coil [Member]
Revenue from Contract with Customer, Including Assessed Tax	21,672,147	21,001,358	55,561,017	77,603,435
Tubular [Member]
Revenue from Contract with Customer, Including Assessed Tax	6,829,902	7,149,459	21,327,312	31,518,282
Operating Segments [Member]
Operating profit (loss)	3,507,000	(561,000)	3,513,000	(1,095,000)
Segment assets	61,443,000		61,443,000		59,554,000
Operating Segments [Member] | Coil [Member]
Revenue from Contract with Customer, Including Assessed Tax	21,672,000	21,001,000	55,561,000	77,604,000
Operating profit (loss)	3,238,000	(93,000)	3,529,000	575,000
Segment assets	43,880,000		43,880,000		35,895,000
Operating Segments [Member] | Tubular [Member]
Revenue from Contract with Customer, Including Assessed Tax	6,830,000	7,150,000	21,327,000	31,518,000
Operating profit (loss)	269,000	$ (468,000)	(16,000)	$ (1,670,000)
Segment assets	17,563,000		17,563,000		23,659,000
Corporate, Non-Segment [Member]
Segment assets	$ 17,926,000		$ 17,926,000		$ 17,790,000