Hi!
Finally, my second 907 clone iron arrived.
I wanted this to be the iron for the "bigger" jobs, so I took a big bevelled tip. I did not do the copper sheet mod yet.
I calibrated the heat using the lead wire melting method, and I had to set my control to 315°, not a big difference to my first iron.
The performance was, however, not very great compared to my Weller.
So I took a close look at the tip, which sat farely loose on the ceramic heater, and noticed that there was a kind of thin-walles stainless steel tube inside the hole. It was farely loose, and was easy to pull out with round pliers. The id was now around 4.35mm.
So I put the tip in the chuck of my drill press, a 5mm drill in my vise, and opened up the hole to 5mm. A 5mm/4mm brass tube was easy to hammer in, so it was a nice tight fit. I deburred the end, folded the copper foil around the ceramic heater, and reassembled everything.
Wow, quite a difference. First thing I noticed was that I had to adjust the heat at the controller to 260° now to melt lead wire with the usual 330° poti setting. Also, it was able to melt the aforementioned test joint much quicker.
I have a little piece of copper sheetmetal with a heavy wire soldered at one end and a blob of solder at the other. I compare irons by sticking them into the blob of solder and counting the time until the solder melts and causes the big wire to fall down.
Weller WS81 - 17s
Hakko 907 clone stock - 37s
Hakko 907 clone mod - 21s
That's not quite as good as the Weller, but almost twice as fast as stock. That's what I call an improvement.