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Question about pipe taps

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markba633csi

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#1
Is there such thing as a bottoming pipe tap? It seems the standard plug type NPT tap can't always go far enough on a shallow hole..but if I grind off the end of the tap then I'll have trouble starting it..
Mark S.
 

4gsr

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#3
They don't make a "bottoming" pipe tap.
What you do is start the thread with a standard pipe tap, then take one and grind off the end to where you need it to go. Try to chamfer the starting edge so it will cut and finish the thread.
I have several in my stuff just for this application.

Jim beat me to it!
 

4gsr

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#5
Yeah, I bet they do. Made to order. I know of one tool supplier in Houston that may stock them, most likely special order them for you.
 

Billh50

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#6
Used to use them for a lot of aircraft work years ago. That and porting tooling.
 

markba633csi

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#10
Thanks, I just squeeked by with a standard tap but I'm putting some used pipe taps on my to-get Ebay list
Mark
 

ch2co

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#11
Hey guys. I was under the impression that NPT taps are tapered. If this is the case how can you just grind off the end of a second tap and finish the threading to the bottom of the hole without changing the taper of the previously tapped upper section? Do you grind off the bottom part of the taper threaded “pipe” to get a tight fit? Or am I just not seeing this the right way which is probable for me.
 

bfd

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#12
ch2co what they are talkind about is tapping a hole that is too shallow for getting a full thread in the hole. first you tap the hole and see if your pipe or fitting fits. if not grind off the first couple of threads and retap the hole. do this until you get the pipe/ fitting to fit. the shorter the tap the larger the top of the tapped hole will be. bill
 

ch2co

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#13
Bill
That’s somewhat what I was getting (trying to get) at. The hole has a bottom in it (not a thru hole) and you first tap the hole as deep as is possible with the NPT pipe tap. Then you use a tap with the end ground off that will just start threading into the tapped hole then finish tapping the hole with the ground off tap so as to get full threads (or close to) to the bottom of the hole. In so doing you will also be enlarging the threaded portion of the top of the hole due to the taper.
This is where I left the previous discussion.
So you now have to cut off the bottom threads of the NPT tapered and threaded pipe end. And suddenly it all makes sense to me and I see what your getting at. Sorry, it’s been a long hard day for an old man.
Thanks
CHuck
 

Silverbullet

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#14
You could grind one down with spindex 5c and a grinder. We had a grinder set up in a valve manufacturer I worked at they just put them in and advanced it to the grinder cutting the bottom row or two off the tap. They looked funny with the tip ground down most left the center hole for sharpening .
 

markba633csi

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#15
Actually Chuck what you find is you usually don't have to cut off the bottom threads of the pipe end. You'll end up hopefully(after using the 2 taps) getting the first few
threads of the pipe to engage; you WANT the hole to be enlarged at the top since it wasn't enlarged enough by running the first tap only partway into
the hole. Yes if the threaded section of the pipe is quite long you might have to take off a little. I've found some variability working with 1/8" and 1/4" sizes.
Mark S.
ps just found some good used taps on Ebay for a great price. More tools, more fun. Less wallet. :)
 
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cathead

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#16
I have a set of tapered reamers to match the taper of pipe taps that I got from a friend.
Maybe using a reamer first would be helpful in running in pipe taps. I'm really not sure on this
but thought this information might be useful to someone. I have not used these yet but they make
sense since the threads are tapered. If nothing else, it would make the threading part easier...

Here's a photo:
 

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bfd

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#17
ch2c0 maybe we can share senior moments together I have been there and done that bill
 

RandyM

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#19
Would it be easier to just use a non tappered pipe tap?
Tapered threads are for sealing in the use of gas and liquid connections. Straight pipe threads are for mechanical connections and not intended for sealed connections. It totally depends on the design intent. Running a straight thread through a tapered thread would just make it a straight thread.
 
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