Forming threaded lipped holes in kettles

[AiredAle]

I added a reply to the long "Soldering Stainless Steel" thread a couple days ago describing how I had formed a tapered lip on a hole in a keg lid, and threaded it to accept a 3/8" nipple. Someone (MacBruver) asked me for pictures.

I thought I'd start a new thread, so this doesn't get lost in that 18 pages and growing thread.

Here is my original description of what I did:

I was inspired by the posts in this thread about pulling a tapered fitting through a small hole to make a lipped hole for increased solder surface area to try something slightly different (see page 8 or so of the Soldering thread). Instead of having the sides of the lip parallel and at right angles to the wall of the keg, I wanted to make the lip tapered at the same angle as a tapered pipe thread. Then I wanted to thread it inside so I could screw in a nipple or reducing fitting, then solder it. My reasoning was the added mechanical strength from threading would improve the overall strength of the joint.

So I chucked a 3/8" nipple in my friend's lathe, and with his help we cut the threads off leaving the taper, then turned a little more taper on the first 1/8" of the "tool". I drilled a 1/2" hole in an old keg head left from keggle making and pulled the tapered tool through the hole about 3/4 of the way down its tapered section. I got a nice 1/16th inch lip that I was able to thread easily and just as easily screw the other end of the nipple into. It works great. I got about 2 full threads cut in the lip. Next will be to solder it to seal it up.

I did have to fiddle around to find the right size backup die to fit onto the back of the hole; too large a diameter and the lip didn't form, I just got a big dimple in the keg top. Too small a diameter and the tapered tool jammed before forming the lip.

I'm going to use this technique for all my small keggle holes for thermocouples and sight glasses. Either fitting nipples or 3/8" to 1/4" reducing fittings. I'll let you know how it works out, but right now I expect it will be great.

So, here are some pictures, of the tool and the threaded hole and with the nipple screwed in place. I was able to cut about 2 full threads in the lip. The hole I ended up happiest with is the one on the left in the picture, the rest are learning experiences.

 

[GreenMonti]

This is very interesting. I like the use of the toll and the ingenuity you have. I guess I am interested in what's next. Do you plan to solder in a long or short nipple? If so, will it go far enough inside to be able to make an inner connection?

The hole as it is now is prime size to start at for a 1/2" coupling (7/8") to be pulled through. If you decide to do so, you will need to grind the flare flush as the pressure needed to pull a coupling with that much flare is intense. I use my 3/8" impact gun to do the work. I get couplings pulled through in just a min or so. This includes setting up the tool.

 

[pickles]

These are for his thermocouples and sightglasses according to the OP. So I don't think he'll be making an inner conection with these specific fittings. I think thats what I gathered from the OP.

 

[GreenMonti]

These are for his thermocouples and sightglasses according to the OP. So I don't think he'll be making an inner conection with these specific fittings. I think thats what I gathered from the OP.

I got lazy and did not read. Thank you

 

[AiredAle]

GreenMonti,

Next will be to silver solder a short nipple, or a street elbow or a 3/8" to 1/4" reducing fitting in place, depending on what device is going into the hole. I'll taper a 1/2" coupling as well to flare holes for where ball valves will be soldered.

If you press the tapered tool in deep enough, or the threads on a nipple are cut deep enough, then you might be able to make an inner connection as well. One of the reducers I have threads almost all the way to the hex section in the same hole that the long nipple in the picture is sitting in.

 

[Bobby_M]

That's one of the beauties of split die threaders. You can intentionally mis-calibrate the cutting heads to let the male thread go further into the female. In this case, you can probably do the same job by bottoming the tap out.

 

[MacBruver]

Very nice!! I will definitely be using this method for putting some holes in my stainless kettle. Thanks for the pics!