bushing 20 bearings 18 and thrust button 22 the seals 37 and or 39 also prevent deleterious materials from entering into the cone 16 and causing premature bit failure due to bearing failure fig2 is an enlarged partial cross sectional view of a portion of fig1 illustrating the embodiment of pressure compensating assembly 30 in more detail referring to fig1 and 2 pressure compensating assembly 30 includes reservoir cap or body 38 o rings 40 and 42 encircle the exterior of body 38 to seal the lubricant from the downhole environment cone support arm 14 comprises annular o ring grooves 80 to house and secure o rings 40 and 42 body 38 includes several radial perforations 46 to provide fluid communication between lubricant located in a hollow interior 48 of body 38 and the lubricant passageway 26 the interior 48 is exposed to the interior of diaphragm 32 which is also initially filled with lubricant the diaphragm 32 has an annular lip or rim 50 that is disposed between lip 52 that is formed in the interior of the body 38 and piston disk 54 to retain diaphragm within interior 48 the body 38 has a fill passageway 64 extending axially through the body 38 and intersecting the interior 48 a removable plug 62 may be positioned into the fill passageway 64 pressure compensating assembly 30 includes snap ring 56 encircling the exterior of body 38 to capture the assembly 30 within cavity 28 plug 74 may secure assembly 30 tightly against snap ring 56.