can this be done??

[imagineers]

I am designing a part. Stainless steel, g1/2 thread. I was wondering if its possible to create the shelf around the thread as seen in the picture. I would prefer to have the thread go all the way to the bottom as seen in one of the pics, but I am not sure if any of this is even possible by machining? its almost like an undercut. the one with the tnread stopping before reaching the bottom seems more possible, but would like advice on this. The reason for this groove is to put an o-ring there. Thanks

 

[imagineers]

MORE PICS

 

[JNieman]

I would say no.

One reason is that there may not be enough clearance between your collar and the thread to allow the threading tool to go that deep without hitting the collar. Or, if a threading bar is able to get in there to cut, there may not be enough room to retract, before pulling out.

Second, a threading cutter only has complete 'teeth' as in, a full vee-shape cutter. You can't push that full triangle into the shoulder to achieve a full thread down to the increasingly disappearing as the thread approaches the wall.

You can, however, provide some thread relief at the end of the thread, though, quiet easily.

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[Compositepro]

I cannot imagine why you would actually want to do what you are asking. What is the purpose? The normal approach is to end the thread a little before getting to the seal face. Almost anything is possible but there has to be a reason to do something extraordinary, or for anyone to help you with this.

 

[imagineers]

The reason for the collar is to create a stop point on the mating valve body to ensure I have the correct face seal compression on the o-ring. If I do not have this collar then the you could just tighten the fitting on until the oring pops off, its a straight thread. I don't want to realy on a torque setting on the fitting either to ensure proper compression either. so could the thread be created up until the top of the collar face with some slight relief past it? and is it possible to create this collar if I pulled that thread up a little?

 

[imagineers]

Here you see the thread only goes to the top of the collar face and not down into that groove....

 

[JNieman]

This is a very basic issue that has a very common standard solution to provide thread relief. Here's my quick scribble to illustrate:

You simply make a reduced diameter at the base of the thread, typically about the same as the minor diameter of the thread. This allows fasteners to continue on past the threaded portion without bottoming out on the unthreaded shaft that remains until the shoulder.

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[imagineers]

JNieman..... like this ?

 

[JNieman]

That's the ticket. That's common practice. I've seen many designs simply point to the corner and say "Min thread relief" or "Thread Relief As Required" which doesn't /"legally"/ constrain manufacturing very well, but it's such a commonplace thing that you're pretty safely going to get what you desire from any semi-civilized manufacturer. However, you could call out thread relief with a "max" dimension to "first full thread" from the face, if you wanted to constrain them, but not beyond practicality.

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[Compositepro]

The last drawing is close, but the thread has to stop at least one thread pitch before the face seal (you cannot get the cutting tool that close to the face. Look at some of your earlier drawings, which show a half cut thread. How is that possible with a vee shaped cutting tool?

An easier and more common approach is to make the o-ring groove ID the same as the thread OD. You will have a more reliable seal if the o-ring is supported on ID and OD. This may also allow the use of a thinner o-ring, so the OD does not have to increase.

 

[imagineers]

went with this, and pull the thread back a little more. it's a g1/2 thread and only 4 threads engagement but I think it should be ok ?

 

[berkshire]

That ought to work ,if you use an offset single Vee tooling point.
B.E.

You are judged not by what you know, but by what you can do.

 

[Compositepro]

Why are you not making the ID of the o-ring grove equal to or larger than the OD of the thread?

 

[hydtools]

See page T36:

http://www.parker.com/literature/Tube Fittings Division/General_Technical.pdf

ISO1179

Ted

 

[imagineers]

@ hydtools... I know about the SAE Straight Thread O-Ring Port, however the seal will be a face seal and I cannot control the fillet and o-ring seating on the valve itself as it is off the shelf, the reason mainly for the o-ring is to provide better leak protection than simply using loctite or some silicon sealing once engaged. I cannot really follow the SAE o-ring boss type seal design in this case.

@compositepro...I never made the shelf inside as I wanted to ensure the compression on the o-ring insteading of stopping out on the thread or the feature you are talking about, I thought a relief would be best as you will guarantee compression and a stopping face where I want it. If that makes sense. I will get samples in to test.