I recently bought a Hakko FX 888D and it’s awesome. So much easier to solder and to solder clean shiny joints. When I was soldering to a big copper slug I cranked up the temp and it took a long time to make the joint between the slug and the driver and the whole thing became very very hot. Obviously the slug is going to heat up but I did not think it would heat up that much or take as long. It could have been my technique or my lack of experience working with a large piece of copper. It was twice as fast as using my old Sears soldering iron but it left me curious. How can I accurately test to make sure the iron is getting to the indicated tip without spending more than $20 or $30 - or is that a pipe dream?
Maybe you need to break out the bottle of mapp gas or propane and use some good flux. Soldering copper to other metals like stainless steel with no lead silver require some skill too. I dunno anyone who does it their first try so don’t feel bad. But finding the right flux RubyFluid Liquid and Paste Flux | Superior Flux & Mfg. Co.
It’s not just possible but you can solder these metals together and hold good pressure too. Make sure the parts are cleaned with a good wire brush before the join
Hakko FG-100 Tester …10USD on China e-Bay… 
Dip it in your coffee and see how long it takes to boil?
Copper wicks the heat away SO fast, it takes a high wattage to really make a spot solder on a big piece of copper. I’m sure your iron is doing what it’s supposed to, loving my 888 analog model. But the bigger pills are definitely a PITA. I always sucked at soldering, but the Hakko station has really upped my game tremendously and I’m far more confident now because of it. There are still things I suck at, like soldering the ground ring of a driver to that big copper pill/heat sink, but I’m learning. (I crank the station all the way up, touch the iron on the pill for about 20 seconds then roll it over to the driver and apply the solder, that has been giving me a pretty good small spot solder…just make sure you don’t leave the iron on too long at that level or it’ll kill the tip.)
And for the record, I really can’t recommend sticking a soldering iron to your tongue or touching it with your finger. 
What about sitting on it (while wearing polyester pants)… a rather corpulent friend of mine did that… once… got him rather good in the danglies…
$6.39. Includes temp probe.
| Temperature | -40°~1832°F (-40°C~1000°C | ±(1%+3) |
Bingo! Cool find and it matches.
I looked at the multimeter option as well and in the reviews a lot of people complained that the temp sensor was way off. Not that the Hakko solution wouldn’t be off but I like it.
Thanks BLF!
Is it likely that an ebay version of this product at $12 could be as accurate as the name brand $200 item?
Of course… Chinese crap sellers would never lie now, would they? Say it ain’t so. Please.
That’s a good point. How often is the Hakko 888 out of adjustment versus how much practice do I need. Maybe this is a case of the carpenter blaming the tools.