Geographic Information (Detail) - Financial information about foreign and domestic operations and export sales (USD $)	3 Months Ended		9 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012
Revenues from sales to unaffiliated customers:
Revenues from sales to unaffiliated customers	$ 1,416,698	$ 1,514,673	$ 5,002,418	$ 4,538,944
United States [Member]
Revenues from sales to unaffiliated customers:
Revenues from sales to unaffiliated customers	217,000	328,000	654,000	855,000
Asia [Member]
Revenues from sales to unaffiliated customers:
Revenues from sales to unaffiliated customers	559,000	527,000	2,503,000	1,814,000
Europe [Member]
Revenues from sales to unaffiliated customers:
Revenues from sales to unaffiliated customers	627,000	652,000	1,810,000	1,835,000
South America [Member]
Revenues from sales to unaffiliated customers:
Revenues from sales to unaffiliated customers	3,000		5,000	2,000
Middle East [Member]
Revenues from sales to unaffiliated customers:
Revenues from sales to unaffiliated customers	10,000	7,000	28,000	17,000
Other Foreign [Member]
Revenues from sales to unaffiliated customers:
Revenues from sales to unaffiliated customers	$ 1,000	$ 1,000	$ 2,000	$ 16,000