What is the Relationship Between Thread Depth to Drill Depth?

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Neelamegan Active Contributor Join Date: Feb 2009 Posts: 11	What is the Relationship Between Thread Depth to Drill Depth? 07/01/2010 10:55 PM
	Dear, What is the relationship between thread depth to drill depth? I have doubt on the above mentioned subject for a prolong time . any one clarify me , i need in metric size
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lyn Guru Join Date: Oct 2008 Posts: 42355 Good Answers: 1693	#1 Re: What is the Relationship Between Thread Depth to Drill Depth? 07/01/2010 11:23 PM
	One is deeper than the other. Do you know which one it is? And does the word "depth" have anything to do with either "blind" or "through"?
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mike k Guru Join Date: Apr 2008 Location: Bristol, Tennessee Posts: 1177 Good Answers: 58	#2 Re: What is the Relationship Between Thread Depth to Drill Depth? 07/01/2010 11:38 PM
	A standard tap is tapered, it does not tap to the bottom of the hole. The drilled hole goes further into the metal than the tap, to avoid bottoming the tap in the hole and breaking it, and it makes space for chips, for the same reason. To tap a hole to the bottom requires a special bottom tap, has more risk of breaking the tap, and takes a lot more time. __________________ mike k
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TVP45 Guru Join Date: Jul 2007 Posts: 4448 Good Answers: 143	#3 Re: What is the Relationship Between Thread Depth to Drill Depth? 07/02/2010 7:28 AM
	There is a common standard taught in school which says the drill depth should be deeper than the thread by 3 times the pitch. This standard was apparently designed by guys who sell taps to replace the ones that get broken by following this rule. Real rules are: Use through holes if possible. Those chips have to go somewhere. How about down and out? Otherwise, please allow the machinist to choose a drill depth that he likes. He's probably been doing this for years and years; he knows what works for his setup. You can add a note to "Not break thru" if you're worried about that. __________________ "Well, I've wrestled with reality for 35 years, Doctor, and I'm happy to state I finally won out over it." Elwood P. Dowd
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ad016 Commentator Join Date: Sep 2006 Location: Wimborne, Dorset. UK. Posts: 77 Good Answers: 2	#4 In reply to #3 Re: What is the Relationship Between Thread Depth to Drill Depth? 07/09/2010 2:48 PM
	Sound advice, TVP45. GA from me. It might be worth mentioning thread milling for larger holes, our guys on their CNC machines can get to within about 1.5P of the bottom face of a flat-bottomed hole, depending on the inserts used. Useful if you are short of space and need max thread engagement. Drew
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