Bore measuring tool

1. An apparatus for measuring a well bore wall comprising:

a casing connectable in line with a tool string having a central passage therethrough and extending between first and second ends;

a plurality of longitudinally extending biasing elements extending longitudinally along said casing wherein a second end of each of said biasing elements is connected to said casing;

a sensor located along a midpoint of each of said biasing elements;

an engagement body located within said central passage of said casing longitudinally displaceable therein between first and second positions, wherein said engagement body is connected to a first end of each of said biasing elements such that displacement of said engagement body within said central passage from said first to said second positions compresses and radially extends said biasing elements so as to engage said sensors against the well bore wall; and

wherein said central passage has a first portion proximate to said first end of said casing and a second portion at a middle thereof, wherein said second portion of said central passage is larger than said first portion.

2. The apparatus of claim 1 wherein said first and second portions of said central passage include an annular shelf extending therebetween.

3. The apparatus of claim 2 wherein said engagement body comprises a disk.

4. The apparatus of claim 3 wherein said disk has a diameter larger than said first portion so as to be retained within said second portion.

5. The apparatus of claim 4 wherein said disk includes a plurality of bores therethrough.

6. The apparatus of claim 5 wherein said plurality of bores are positioned to be sealed by said annular shelf when said disk is engaged thereon.

7. The apparatus of claim 2 further comprising a transfer body positioned within said first portion of said central passage being displaceable therein.

8. The apparatus of claim 7 wherein said transfer body has a leading edge adapted to receive a dropped ball thereon.

9. The apparatus of claim 8 wherein said transfer body has a length selected to be located within said second portion of said central passage at said second position of said engagement body.

10. The apparatus of claim 1 wherein said casing includes a plurality of longitudinal slots extending therealong.

11. The apparatus of claim 10 further including a carriage located in each slot.

12. The apparatus of claim 11 wherein each of said carriages is connected to said engagement body.

13. The apparatus of claim 12 wherein said biasing elements extend along said slot.

14. The apparatus of claim 13 wherein each of said biasing elements extend between said carriage and a distal end of said slot.

15. The apparatus of claim 1 wherein said biasing elements comprise springs.

16. A method for measuring a well bore wall comprising:

providing a casing in line within a tool string;

displacing an engagement body within a central passage of said casing from a first position to a second position to compress and radially extend a plurality of longitudinally extending biasing elements connected thereto;

recording at least one measurement of the well bore wall with a sensor located on each of said radially extended biasing elements; and

wherein said central passage has a first portion proximate to a first end of said casing and a second portion at a middle thereof, wherein said second portion of said central passage is larger than said first portion.

17. The method of claim 16 wherein said displacing said engagement body comprises engaging a blocking body upon a transfer sleeve above said engagement body, applying a pressure to a top side of said blocking body and said transfer body and displacing and said engagement body under said pressure.

18. The method of claim 16 further comprising uncovering at least one bypass port through said engagement body at said second position.