Here's an example using a TBlobStream:

procedure TForm .Button Click(Sender: TObject);
var
  BS , BS2: TBlobStream;
begin
  BS  := TBlobStream.Create(Table Notes,bmRead);
  try
    Table2.Edit;
    BS2 := TBlobStream.Create(Table2MyBlob,bmReadWrite);
    try
      BS2.CopyFrom(BS ,BS .Size);
    finally
      BS2.Free;
    end;
  finally
    BS .Free;
  end;
  Table2.Post;
end;