Note J - Segment Information - Segment Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020
Revenue from Contract with Customer, Including Assessed Tax	$ 24,861,680	$ 39,995,580	$ 48,386,280	$ 80,970,900
Operating profit (loss)	(317,046)	(2,036,499)	(1,457,999)	(1,773,563)
Corporate expenses	718,000	614,000	1,452,000	1,241,000
Interest expense	6,255		12,208
Interest and other income	(4,325)	(4,370)	(8,648)	(10,705)
Total earnings (loss) before taxes	(312,721)	(2,032,129)	(1,449,351)	(1,762,858)
Segment assets	73,048,145		73,048,145		$ 77,344,088
Coil [Member]
Revenue from Contract with Customer, Including Assessed Tax	18,456,086	28,420,609	33,888,870	56,602,077
Tubular [Member]
Revenue from Contract with Customer, Including Assessed Tax	6,405,594	11,574,971	14,497,410	24,368,823
Operating Segments [Member]
Operating profit (loss)	407,000	(1,422,000)	6,000	(533,000)
Segment assets	53,345,000		53,345,000		59,554,000
Operating Segments [Member] | Coil [Member]
Revenue from Contract with Customer, Including Assessed Tax	18,456,000	28,421,000	33,889,000	56,602,000
Operating profit (loss)	751,000	324,000	291,000	668,000
Segment assets	33,689,000		33,689,000		35,895,000
Operating Segments [Member] | Tubular [Member]
Revenue from Contract with Customer, Including Assessed Tax	6,406,000	11,575,000	14,497,000	24,369,000
Operating profit (loss)	(344,000)	$ (1,746,000)	(285,000)	$ (1,201,000)
Segment assets	19,656,000		19,656,000		23,659,000
Corporate, Non-Segment [Member]
Segment assets	$ 19,703,000		$ 19,703,000		$ 17,790,000