Drilling of a Small and Deep Hole Using a Twist Drill.

Deep hole drilling with a depth of ten times a small hole diameter is used in the automobile industry. In the previous paper the author investigated drilling of holes with depth of up to five times the diameter, and showed that vibration drilling is effective for this. This paper concerns chip formation and disposal in drilling of holes with depth of ten times the hole diameter. The results are as follows. When a deep hole is drilled, contact resistance between chip edges and the hole wall increases and produces chip congestion. Increase of the feed speed helps to prevent this congestion. Vibration drilling disposes of chip easily at a fast feed speed because it accelerates the penetration of oil and produces a large variation of chip thickness. Easy chip disposal in vibration drilling extends drill life in comparison with conventional drilling.