Superiorwelding wrote:Also, one problem I ran into working on my Unbreakable TIG Cup™ was if the cup i.d. (at the exit) was larger than the gas lens itself your coverage is extremely poor. To use a larger cup than the gas lens you must have a secondary diffuser, as you see with all the large cups out there. If you wanted to make these cups work, and assuming the gas lens' themselves are "good" simply add a second diffuser and your coverage should improve.
Jonathan
I agree 100%.
OP, if you notice, most "standard" gas lens, meaning medium-large that use regular pink alumina cups, all "stop" the cup size when the cup exit is the same size as the screen mesh (and even then, they still have a slight taper).
For example, if you are using a medium gas lens collet body on a 17/26 torch, I doubt you'll find many, if any at all, alumina cups that are larger than a #8. If you want an alumina cup larger than #8, you typically have to switch to a large diameter gas lens collet body.
If you are using a large diameter gas lens collet body, the largest you'll typically find is #12. If you look at the mesh screen on a large dia. gas lens collet body, turns out the mesh screen is about, yup you guessed it, 3/4"---the same size as the #12 cup exit orifice. The exception is the #15 cup. It doesn't really look like a cup, more like a thread on protector----it just covers the collet body and does not aid with maintaining laminar gas flow. I have one, and while it worked, the gas covered just wasn't what I felt "it should be" for that large of a "cup".
IMO, it's the same reason, the Furick FUPA cups have the mesh screen/diffuser in the first place----the tiny mesh on the gas lens collet body that it installs onto is simply not going to produce the laminar gas flow that is needed for good coverage.
I'd like to test my hypothesis with your gas lens, if you'd like. I still have some mesh screen left over from my experimentation, I can punch out some screens for you to try out. Just let me know what size tungstens you are using.