In my line of work doing HVAC most of the other guys carry around a cheap duct knife with no sheath and one of these while running duct work.
They definitely sharpen really fast but I see them sharpening constantly throughout the day. Their duct knives usually go from a wharncliffe type shape to a
really lazy hawkbill type thing, in other words, sunk in the middle. These sharpeners don't really sharpen the entire edge and they wear metal down quickly.
However, if its a cheaper knife and you care more about getting an edge quickly than a "proper" edge, these really are the way to go.
Personally, I usually use a serrated Salt Series from Spyderco when running a whole house/ business worth of duct work, because they cut well all day with no sharpening needed.
I find they cut better than the plain edges they use. With that said, the guy who taught me how to run duct work uses a cheap knife and pull through sharpener and his duct work looks better
than mine still. On the other hand, if I ever let them borrow my one of my Spydercos, it can be hard to get them to give it back before the work day is over because
"man this thing just keeps cutting, mind if I use it today? I bet you have another one right? as much as you love knives?"
They're not wrong but it's irritating, so I did what any good knife lover would do, I gifted them some of the blades I don't use anymore like a SOG and a Benchmade because my Salt Series are not for cutting
PVC and reaming EMT

and my CRKs are not for trimming roof flashing or prying/ cutting sheet metal



Good group of guys


but hell on a knife

