I heat up a screwdriver with a blow torch and use that. I know the temp is right when the screwdriver tip starts turning red.
I am only kidding but I wanted to fit in
Seriously though, I looked up a couple of datasheets that mentione lead temperature bacause other than I use my 18W iron unless I need more heat and then turn the 25W on, I didn't have a numerical answer
260-300 Celcius ( 500-572 Farenheit) seems to be the numerically correct answer. The rest is kinda like my blowtorch joke
I looked up a 1N4001 diode and I picked one of the LM317 Voltage regulator variations from the Datasheets on Digikey.
Lead temperature according to the good folks at Vishay for their 1N4001 is 275C (572F)http://www.vishay.com/docs/88503/1n4001.pdf
National Semiconductor specifies 260C (500F) or 300C (572F) depending on metal or plastic packaging of the LM117 http://cache.national.com/ds/LM/LM117.pdf
Depending on components and skill level I would stick with something in the 550F to 600F range