wxpython - wxtoolbar font size

[Ghido]

Hi all i want to set wx.toolbar font size and i use this code:

self.tb1 = wx.ToolBar(self, -1, style=wx.TB_HORIZONTAL|
                                    wx.TB_TEXT)
self.tb1.SetFont(wx.Font(9, wx.DEFAULT, wx.NORMAL,0))
self.SetToolBar(self.tb1)

but i obtain nothing. Is possibile? where i wrong?
I use wxpython 2.6.3 on ubuntu edgy
thanks

Ghido