been moved down from the upper string mill 24 to the connection between the window mill 30 and the string mill 32 this is schematically illustrated by comparing fig2 and 4 those skilled in the art will appreciate that the present invention allows for shorter bottom hole assemblies and lateral exits at far shorter radii than had been possible with previous designs the angle on the whipstock face has been altered to a range of greater than 3 5 u00b0 with the preferred range of 4 u00b0 to 5 u00b0 at the same time the maximum dimension of the assembly where the whipstock is connected to the window mill has been reduced to less than 95 of the casing drift diameter with the preferred range being 70 u2013 75 of the drift diameter preferably as shown in fig6 the string mill 32 can have the same outside diameter as around the whipstock 34 and the window mill 30 alternatively the string mill can be somewhat larger optionally there can be only one string mill 32 but use of more than one string mill is within the scope of the invention ultimately after the window 38 is milled with the assembly.