REVENUE - Disaggregation of Revenue (Details) - USD ($)	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
Disaggregation of Revenue
Net sales	$ 6,346,000	$ 4,473,000
Domestic
Disaggregation of Revenue
Net sales	6,098,000	4,094,000
Foreign
Disaggregation of Revenue
Net sales	248,000	379,000
Commercial Aerospace
Disaggregation of Revenue
Net sales	2,410,000	1,760,000
Defense
Disaggregation of Revenue
Net sales	3,823,000	2,277,000
Industrial
Disaggregation of Revenue
Net sales	113,000	436,000
Magnetic components
Disaggregation of Revenue
Net sales	3,254,000	2,157,000
Potted coil assembly
Disaggregation of Revenue
Net sales	1,519,000	1,279,000
Electro-mechanical assemblies
Disaggregation of Revenue
Net sales	$ 1,573,000	757,000
Large transformers
Disaggregation of Revenue
Net sales		$ 280,000