TD 51 should be a good unit. I owned a TD 38 for three years and then six months ago I traded it in on a Cutmaster 81. I needed more power, 'cause I frequently mount the torch in the NC cutting table I built. This doubles the power requirement for a given gauge. I used the 38 real hard for those three years and it alway worked fine, never shutdown from overheat or anything, and gave a very nice fine kerf if you were patient. The real limit of that machine when using the torch handheld was about 1/4". In the NC table, I could not cut greater than 1/8" with acceptable quality.
Overall, Thermal Dynamics is great product. Just make sure you buy a big enough one to do what you need done. If in doubt (or if you are doubting the manufacturer's ratings) take some steel to the dealer and ask him to let you cut thru it. And, try curves instead of all straight lines, it seems to take more power or lower pass speed. See ya...
