Threading to a shoulder?

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DianneB
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Threading to a shoulder?

Post by DianneB » Sat Nov 03, 2018 5:21 pm

I have a bunch of 1/4" check valves to make (for cold water) and made a first attempt today.
SNB12910.JPG
The two halves of the valve thread together with a 3/8-24 thread but even reversing my die to finish the male threads, I can't get as close to the shoulder as I would like.

Is there a way to get close to the shoulder (without grinding up a custom tool bit and threading on the lathe)?

BTW: It works fine.

James Powell
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Re: Threading to a shoulder?

Post by James Powell » Sat Nov 03, 2018 5:31 pm

What about dropping a parting tool in between the thread and the shoulder after threading? (or before, for that matter)

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DianneB
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Re: Threading to a shoulder?

Post by DianneB » Sat Nov 03, 2018 5:37 pm

James Powell wrote:
Sat Nov 03, 2018 5:31 pm
What about dropping a parting tool in between the thread and the shoulder after threading? (or before, for that matter)
I have very little wall thickness at that point but will try that tomorrow. I DID use a countersink in the female thread. I need about 0.100" more engagement.

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ChuckHackett-844
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Re: Threading to a shoulder?

Post by ChuckHackett-844 » Sat Nov 03, 2018 5:56 pm

Can you make the male part longer to get more thread?

You might be able to grind the back side of the die to get closer (don't suppose you have a surface grinder?).

Since you said that you reversed the die I assume that this us not a pipe thread. You could turn off the hex from the male, thread the entire part, and then use a nut to lock the parts. You could even solder the nut on and again have a fixed nut/shoulder.
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hoppercar
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Re: Threading to a shoulder?

Post by hoppercar » Sat Nov 03, 2018 6:15 pm

Take the male end with the hex.....drill and tap it all the way thru...loctite in your threaded stud at the length you want it to protrude past the hex, the top side can be faced off, or turned to any other size you wish if you leave enough material sticking out.

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NP317
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Re: Threading to a shoulder?

Post by NP317 » Sat Nov 03, 2018 6:56 pm

Use an o-ring in the joint!
Or relieve the threads in the female hex piece.
~RN

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ccvstmr
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Re: Threading to a shoulder?

Post by ccvstmr » Sat Nov 03, 2018 7:40 pm

Saw your thread title. Is this in regards to fabricating a check valve...for an injector? ...axle pump? ...crosshead pump?

Reason for asking, had a problem several years ago where repeated pounding of the stainless steel check ball against the brass for the exit check valve seat, eventually pounded the opening closed. Then, no water flow and in fact was blowing feed water tubing off the hose barb (system gave way at the weakest point).

To resolve this problem, silver soldered a wafer of bronze (silicone?) on the brass threaded end cap for the pump. Drilled the hole thru. Beveled the hole opening. And then...used a Dremel grinding disk in a hex holder in the mill to cut (6) slots. Total contact area for the check ball was maximized while allowing sufficient opening for water passage when the ball was lifted.

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Builder01
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Re: Threading to a shoulder?

Post by Builder01 » Sat Nov 03, 2018 8:39 pm

DianneB wrote:
Sat Nov 03, 2018 5:37 pm
James Powell wrote:
Sat Nov 03, 2018 5:31 pm
What about dropping a parting tool in between the thread and the shoulder after threading? (or before, for that matter)
I have very little wall thickness at that point but will try that tomorrow. I DID use a countersink in the female thread. I need about 0.100" more engagement.
The groove made by a parting tool only needs to be the same depth as the thread. If you have enough wall thickness for a thread, there is enough wall for a groove to remove only the thread at the shoulder.

David

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DianneB
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Re: Threading to a shoulder?

Post by DianneB » Sun Nov 04, 2018 5:39 am

The check is for crosshead pumps.

Thanks for all the suggestions gang!

I think I will remake the top (male) by threading a piece of rod 3/8-24 and making the hex portion as a nut soldered in place. That will also allow me to set the optimum ball lift.

I'll let you know how it works out.

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tornitore45
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Re: Threading to a shoulder?

Post by tornitore45 » Sun Nov 04, 2018 6:08 am

Just relieve the female part with a major dia for a couple of threads to make room for the unfinished threads on the male part.
Mauro Gaetano
in Austin TX


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Bill Shields
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Re: Threading to a shoulder?

Post by Bill Shields » Sun Nov 04, 2018 8:30 am

Dianne;

you are making this whole process over-complicated.

I just use a threading die to start, then turn the die around, then relieve the threads at the shoulder with a very narrow tool.

in reality, considering the pressures, you only need 2-3 threads to hold the cap in place.
Too many things going on to bother listing them.

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