This Center Roc Roto Loc underreaming bit for QL60 down-the-hole hammers drills an 8.35 in. hole with its wings extended and retracts to 6.50 in. to pass back through casing. The wings lock positively to cut full diameter through any rock formation while advancing casing behind the bit with no expensive starter casing teeth and no sacrificial ring bit left in the hole.

Underreamers earn their keep in cased overburden drilling, where the bit must cut a hole larger than the casing it pulls down. This one runs on QL60-shank hammers such as the Mincon 6BH from our down-the-hole hammer range; the positive-locking wings can even retrieve casing, and wing replacement is quick in the field. The DTH hammer buyer’s guide covers matching hammer, bit and casing, and underreamer sizes from 5.5 in. to 36 in. are available alongside our DTH drill bits.

• QL60 shank; 8.35 in. drilling diameter extended, 6.50 in. retracted for retrieval through casing
• Positive-locking wings cut full diameter through any rock formation and can be used to retrieve casing
• No expensive starter casing teeth or ring bit left in the hole
• Easily retractable wings with simple, quick replacement
• Improved bit face design enhances flushing of cuttings for better productivity
• Underreamer size options from 5.5 in. to 36 in. available
• Concave face, dome carbide configuration; bit weight 108 lb
• Available from Crowder Supply in Denver