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Rolled Internal Thread

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tjhu88

tjhu88

Mechanical
Oct 24, 2012
1
Every Rolled Internal Thread company told me it is impossible to roll tap internal thread on water connectors (for example: female garden hose connector, you will find they are all machined), because they think the wall thickness is too thin and forming taps are not well suited to thin walled parts as they expand and transfer the thread form to the O.D. of the part. But I am not taking the thin wall approach. My approach is to roll form internal thread to an extruded tube with thicker wall and ID approximatey equal to pitch diameter of internal thread, then machine the OD to whatever thickness I need.
Does anybody agree with my concept? Thanks
 
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tj

is it possible to run test. I believe it will work.
you will have to calc the minor dia before roll tapping.
that is the best way. But i believe it will work.

I have worked with external rolled threads but not internal threads.
most of the threads I work with now are machined.
so I do not have thead calc handy I will have to find it.

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.
 
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For your concept forming the thread will be no problem. However rolled internal threads have crest variation problems that may not be leakproof. Testing is warranted.
 
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I agree with Cory, form tapping the internal threads should be possible with sufficient wall thickness. The two links show the appearance of the crest variation, the first one showing an extreme example in a sheetmetal nut:

Conformance of Roll Formed Internal Threads to AS8879

An experimental study on the effects of lubrication in form tapping
 
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Female GHT is normally a 'stopped' thread, i.e. you can't use a normal tapered Express tap because of the internal flange at the proximal end of the thread.

You could whirl the thread, or rotary swage the OD of the part down over a threaded mandrel. I think the thread depth is too great relative to the nominal diameter to, say, form the threads with internal rolls.



Mike Halloran
Pembroke Pines, FL, USA
 
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Here is a nice document
I believe the minor dia of the threads can be adjusted by calculating the correct size prior to
internal thread forming.
I had literature but will have to locate it



Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.
 
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