Have a look at the size of this tricone rotary drill bit: http://imagesignal.comsec.com.au/docserver/01277699.pdf?fileid=01277699&datedir=20120312&edt=MjAxMi0wMy0xMisxMTowNDoxOCsxMjArMCtjb21zZWMrcmVkaXJlY3QrL2ltYWdlc2lnbmFsL2Vycm9ycGFnZXMvUERGVGltZW91dC5odG1sKy9pbWFnZXNpZ25hbC9lcnJvcnBhZ2VzL3BkZmRlbGF5ZWQuanNw