I was a bit fed up with my propane blowtorch because it loses pressure quite quickly and stop delivering the very hot flame necessary to heat the punches to the 'cherry red' point. I don't like canisters and disposable cartridges (I still write with an indestructible Parker 51
) so I decided to try the notoriously unsafe petrol blowtorches as recommended by Paul Koch in his Dolphin's article.
I purchased a mint 'BAT' blowtorch manufactured in the German Democratic Republic
and after reading all the safety recommendation published at: http://www.blotorches.com/horror.html
I gave it a try.
I filled the container to 3/4 of its volumen with benzine (wasbenzine), followed the starting protocol with alcohol (less smoke) and could make it deliver a very hot a powerful blue flame. Then I took a blank punch to the glowing red point in about 3, 4 minutes. Faster and more evenly than with the propane blowtorch. I liked it and I will continue using it.
So, provided you use a petrol blowtorch in good condition, have a lot of care handling a volatile fuel and operate it with proper knowledge of the tool; it's a very useful device for hardening punches.
Please if you decide to try one of these, please learn well how to operate it before doing anything: http://www.blotorches.com/startshu/startshu.html
i would stick to gas. Using a large gas bottle like roofers do. Either Butane or propane. The also come in smaller sizes.
Does anybody have an idea on where, how and what kind of oven for the hardening?
Just something to tell; many years ago as a budding Scientist (where did I go wrong?) we experimented with Carbon steel, heating it then plunging it into liquid Nitrogen, then hitting it causes it to shatter into shards, just something we did to prove that the steel molecules were not sticking together.