Sievert air screw repair

The air screw for my Sievert 4-burner furnace looked ok ...






... but it was allowing a small air leak, symptom of the fuel tank losing pressure, slowly but surely.

I wasn’t happy either that when tightened up too much of the shank disappeared inside the valve.

Not so apparent in this shot but I could tell it was ‘hung up’ in the valve and disrupting the proper seating and hence sealing.




Confirmation that the air screw was worn (threads were sloppy too) was that a spare Primus air screw enabled the tank to maintain pressure, so the valve seat was fine.

I wanted to retain the authentic Sievert grip so set about grafting it onto the unworn Primus air screw spindle.

To strengthen the joint and to prevent the two parts moving out of alignment during silbrazing I machined a tenon on one part and a slot in the other.




‘Dry’ fitted before silbrazing.




Immediately after silbrazing and before washing off the flux and polishing.




The finished component.




Installed on the furnace.




John

 

Very neat little job John

 

Quality fix John. Jerry

 

I had one that even after machining to clean up the tip, I had to file some of the threads off towards the tip so it would screw in further.
Duane

 

Wow, nice work. Creative solution.

 

Simple and effective.

 

Tenon and slot.
Another tip to bookmark from the fettling wizard!
Thanks John.

 

Very nice and I like the precaution you take for a job well done.
Bravo !!!!

 

John, what kind of torch, gas, flux and solder did you use?

 

@Don Octavio
A Rothenberger torch, MAP gas and flux-coated 55% silver 1.5mm cross-section diameter silbraze rods.



John

 

Thanks John. You think one can achieve the same with a propane torch? I'm eyeing one on a Dutch secondhand site. The MAPP gas cans are pretty pricey in comparison to propane or butane cans.

I'm also thinking of this torch on Aliexpress coupled with cheap butane gas canisters, would that work as well?

 

In a word, no. Yes the high-silver content rod could be melted with a very small component to silbraze but anything larger would consume (heat soak/disperse) the heat from the torch away and make melting the brazing rod difficult.

 

Ah, thanks. I'm a layman to this.

I'm a bit surprised how expensive silversolder is here. What brand do you use?

 

And to add:

It's 10 euro's for 50 cm for a 1.5 mm rod with 55% Ag. Do you reckon 50 cm is enough for a couple of projects?

 

This stuff, but there are other brands.




The price reflects the fact that it’s got 55% silver in it. It’s a bit cheaper to get the rods un-coated with flux, requiring flux paste to be made up separately. I get the coated rods for convenience.

Is 50cm enough? Depends on the projects and the extent of the joint to be made.

John