Lelit Bianca Flow Control Valve.
Many thanks again to @thusband for sending me the Lelit Flow control valve. The internal thread in the top nut had stripped and Lelit don’t sell spares, the only option is to buy a complete assembly at over £200, so if you can’t fix the stripped thread the whole thing is useless. So Tom offered the assembly to anyone who could use it and generously sent it to me, wouldn’t even accept something for postage. To compound the issue the thread is very non standard and not easy to replicate. I looked on the whole issue as a challenge with a very desirable outcome if I could succeed.
The real challenge is replicating the thread in the nut. I spent a whole day measuring, looking at tables and even made a tap on my screw cutting lathe.
The tap produced a beautiful thread on a test piece and was perfect, except that it didn’t fit the shaft. Bugger. After much more time and effort I believe that I have solved the problem and made a threaded insert to fit inside the nut. I am not going to say any more on the thread and how I solved it.
I have enough material to make three more inserts and may either sell them or carry out a restoration service on stripped nuts but price will reflect the amount of effort expended to get this far.
The insert is pressed into the nut with a little loctite.
All assembled with the larger gicleur and shorter gauze, new O rings, Molikoted and adjusted. Flow rate fully open is about 5ml/sec., operating smoothly with no leaks.
