Union nuts & cones?

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DianneB
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Union nuts & cones?

Post by DianneB » Tue Oct 09, 2018 9:38 am

I haven't been able to find drawings for making small steam unions for various size tubes and pipes and have some to make over the winter. I looked on the IBLS web site and didn't see anything. Has anyone seen drawings posted?

It looks like a simple task but a few things jump out at me:

Drilling & tapping the union nut would require a square bottom drill. True?
Tapping the union nut would require a bottoming tap. True?

Balancing the thru-hole drill size in the nut and the shoulder diameter on the union cone would seem to be important. I presume the OD of the cone would be turned to a close fit inside the threaded portion of the nut.

Any guidance or advice on proportioning union cones and nuts????

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gwrdriver
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Re: Union nuts & cones?

Post by gwrdriver » Tue Oct 09, 2018 9:43 am

I have a table of these and when I'm back at my home computer later today I'll post it (if I can find it.) IIRC my table is based upon ME threads but the proportions are good for whatever thread system you want.
GWRdriver
Nashville TN

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cbrew
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Re: Union nuts & cones?

Post by cbrew » Tue Oct 09, 2018 9:47 am

DianneB wrote:
Tue Oct 09, 2018 9:38 am
Drilling & tapping the union nut would require a square bottom drill. True?
I would thru-hole drill size then finish the shoulder with a boring bar
DianneB wrote:
Tue Oct 09, 2018 9:38 am
Tapping the union nut would require a bottoming tap. True?
Yes
DianneB wrote:
Tue Oct 09, 2018 9:38 am
Balancing the thru-hole drill size in the nut and the shoulder diameter on the union cone would seem to be important. I presume the OD of the cone would be turned to a close fit inside the threaded portion of the nut.
a couple thou clearance is fine
If it is not live steam. its not worth it.

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JBodenmann
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Re: Union nuts & cones?

Post by JBodenmann » Tue Oct 09, 2018 10:12 am

Hello My Friends
For making the union nut a two flute end mill works fine for a tap drill. If you use a forty pitch thread just use an end mill .032 undersize. Don't bother with taper or plug taps when buying 40 thread taps. Just use a bottoming tap.
Happy Model Building
Jack

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gwrdriver
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Re: Union nuts & cones?

Post by gwrdriver » Tue Oct 09, 2018 10:54 am

I found my fitting table (Cad) but it seems to be incomplete and needs to be checked against my source which was probably published in Model Engineer magazine. I'll see what I can do.
GWRdriver
Nashville TN

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Builder01
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Re: Union nuts & cones?

Post by Builder01 » Tue Oct 09, 2018 11:03 am

Hi Dianne,

As it turns out, I have a "how to" page on my website dedicated to making union cones and nuts. If you scroll to the bottom of the page, there is a PDF of the chart that I have used based on the outside diameter of the tubing. Of course you can adapt it however you need. As for the flat bottom on the inside of the nut, you could use a boring bar, but, it would have to be pretty small. I use, as you suggest, a flat bottom drill bit.

Here's the link to the page: https://supersimplex.yolasite.com/How-t ... -Union.php

I hope you find it useful.

David

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DianneB
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Re: Union nuts & cones?

Post by DianneB » Tue Oct 09, 2018 12:11 pm

Builder01 wrote:
Tue Oct 09, 2018 11:03 am
As it turns out, I have a "how to" page on my website dedicated to making union cones and nuts.
EXCELLENT! Exactly what I was looking for! Now bookmarked :mrgreen:

B&OBob
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Re: Union nuts & cones?

Post by B&OBob » Tue Oct 09, 2018 8:43 pm

Prolific master builder/designer, the late Bill VanBrocklin, designed a series of cone fittings decades ago that have minimum dimensions for each tubing size, making for neat installations without the non-scale oversize appearance of many commercial products. Bill published a table of dimensions for his fittings and that drawing, along with some suggestions for mass-producing cone fittings was the subject of my article in the May/June 2012 edition of the PLS Gazette. available at: http://www.palivesteamers.org/pubs/gaze ... -6-rev.pdf
All recent Gazettes are available at palivesteamers.org

The illustrated article, in addition to listing Bill's designs, offers a clever way to mass-produce cones using a lathe tool designed ages ago by LBSC that, in one setting, produces the proper cone angle and cuts-off the completed cone. You can esily knock out more than two cones in a minute using LBSC's tool and procedure. The article also describes a routine procedure for naking union nuts with a "D-bit" to make a flat-bottom hole with finished I.D. prior to tapping. D-bits, although quite common in the U.K., do not seem be appreciated by many U.S. live steamers for their value in rapid, accurate generation of a flat-bottom hole with precision diameter as typically used in pumps, check valves, and and other water-and steam fittings.

An admirable feature of VanBrocklin cone fittings is the absence of an ugly non-prototypical "tail" on every cone that sticks out beyond the union nut to simplify silver soldering the cone on the tube; compact cones are silver soldered directly on the end of the tube. For neat. realistic appearance, its hard to beat Bill's design!

B&O Bob

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BAdams
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Re: Union nuts & cones?

Post by BAdams » Tue Oct 09, 2018 11:30 pm

David and B&O Bob,

Thanks a bunch for showing us there is more than one way to skin a cat.

Brook

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Fred_V
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Re: Union nuts & cones?

Post by Fred_V » Wed Oct 10, 2018 7:24 am

I also have a CAD drawing of these from 1/8 to 3/8 if you like.
The tricky part is making the male thread for the nut. all of my dies are split dies and I have to open them up when cutting the thread or else the thread will be too small and the nut will be a really sloppy fit.
These are fun to make once you get used to doing it and you can make one in 10 minutes.
Fred V
Fred V
Pensacola, Fl.

B&OBob
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Re: Union nuts & cones?

Post by B&OBob » Wed Oct 10, 2018 9:28 am

Fred, my experience is the same as yours with adjustment of dies for male theads. At 40 tpi (and even 32 tpi) a small change in diameter can make a big difference in fit. Most of my threading tools came from England forty years ago, and for some reason all the dies seem to be optimized for making minimum-size threads. Opening them far enough to produce a tight-fitting, large thread really stresses them. I only broke one die while doing that, but it was enough to influence me to gradually invest in two or three dies for each thread size. Each die was then permanently adjusted to produce a nominally "medium" or "large" thread to suit fitting requirements. Expensive, yes, but a great time saver and no more sloppy fits or that ominous "clink" as the die breaks.

B&O Bob

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Greg_Lewis
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Re: Union nuts & cones?

Post by Greg_Lewis » Wed Oct 10, 2018 9:51 am

By the way, here's another plug for Victor Machinery, who has special thread taps and dies in all manner of threads and diameters. They have 40 tpi in just about any diameter you could want. Prices are reasonable. https://www.victornet.com
Greg Lewis, Prop.
Eyeball Engineering — Home of non-interchangeable parts.
Our motto: "That looks about right."
Celebrating 30 years of turning perfectly good metal into bits of useless scrap.

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