Why is it difficult to process deep hole threads on automatic tapping machines?

Why is it difficult for automatic tapping machine deep hole threads? First, you need to define what a deep hole is and why it needs special consideration. In drilling, those holes with a depth greater than 3 times the hole diameter are called deep holes. Deep hole tapping means that the tapping depth is more than 1.5 times the diameter of the tap. For example, when a 1/4″ diameter tap is used to process a 3/8″ thread, this situation is usually called deep hole tapping.

Why is it difficult to process deep hole threads on automatic tapping machines, mainly because:

1. Deep hole thread is difficult to remove iron filings, if iron filings cannot be discharged, it is easy to break the tap;
2. The automatic tapping machine processes deep threads because it is difficult for cold liquid to enter, the tool cooling is difficult to guarantee, and the lubrication is difficult to guarantee, so the tool is easy to wear or burn out;
3. The automatic tapping machine can’t feed the deep thread too fast. If the feed is too fast, it will easily break the tool.

From: http://www.hi-pre.com/difficult-process-deep-hole-threads-automatic-tapping-machines/