[Rus_boz]

query3.SQl.Text:='INSERT INTO DSO.DB (KN) SELECT 10 FROM Stab.DB WHERE DRAFT = ''' + Edit8.Text + '''';
Чегойто здесь не так )
а попробуй
query3.SQl.Text:='INSERT INTO DSO.DB (KN) SELECT 10 FROM Stab.DB WHERE DRAFT ='+''''+Edit8.Text+''''+';';