Thank you. With the UKPK when my finger is on the choil I can use my thumb to get the blade disengaged and then use my index finger to close the blade. Looking at the Kizer and Hinderer it appears they both have the chiol. So it seems like one could do the same for closing. Anyone have either of these and can confirm they close one handed easily?
I own a lot of the Spyderco Slip Its, the Kizer Zipslip Ti and the Hinderer Slippy. And IMO you can do this with all these knives.
Having said this I will share my experience.
I own(ed):
Böker XS OD (gone)
Hinderer Slippy Slicer 2017 (gone)
Hinderer Slippy Spanto 2019
Kizer Zipslip Ti S35VN (gone)
Spyderco UK PK Lightweight CTS-BD1 (gone)
Spyderco UK PK Red G10 Heinnie Exclusive CPM30V
Spyderco Urban Lightweight N690 (gone)
Spyderco Urban Lightweight Sprintrun K390
Spyderco PITS N690
Spyderco Squeak Sprintrun Elmax with Ti Handle
Spyderco Terzuola Slip It (gone)
Out of all these I still like the UK PKs and the Urbans the best as one hand opening knives. The Lightweight UK PK has a relatively weak spring in comparison, but that's part of what makes it a great OHO. Same goes for the Urbans. The Heinnie G10 UK PK has a rather strong spring. It is not as easy to operate IMO. I suspect that it will run in though, because it has bronze washers! All in all I consider it the best buy of this whole list right now. Heinnie won't charge you VAT if you ask them by email beforehand and if you do so it will cost less than $ 100 bucks. IMO that's a fair amount of money for upgraded handle material (G10 - I hate FRN), blade steel (CPM30V) and bronze washers.
The Squeak is also a good knife but really tiny and I have rather big hands. Since it is titanium it is rather hard to hold while opening IMO.
The Terzuola has this stupid lanyard-thingy at the back of the handle, which makes it a bit uncomfortable IMO. Also I prefer a FFG for most tasks and the detend ball based opening technology IMO is inferior to a classic spring construction: A new knife feels scratchy, an old knife feels lose and even in the time between it feels just okay / like a weak slip joint. When you consider that the Terzuola has quite some collectors value (~200 Euros) nowadays I wouldn't recommend to use it as an EDC, maybe if you get it really cheap. But even then it would probably be better to sell it and get an UK PK.
The PITS is regarded the holy grail of Spyderco Slipjoints and I agree to some degree: It carries great, the blade is the biggest of all Spyderco slipjoints and the lockup is superb. But there are some downsides to it: The Spydiehole only works okayish because it is covered by the grip quite a bit when the knife is closed, the "flippertab" looks a bit odd and the strong spring can sometimes give you a hard time operating the knife - and yes, it might even bite you from time to time. And then it isn't exactly cheap and N690 is okay but not great etc etc. I still really like the knife. The only thing I didn't like about it is how easy the blue wore off (yes, my knife was blue originally, but had deep scratches ~1 minute after taking it out of the box so I removed the rest of it after a few days).
The Kizer Zipslip is a fine knife. It also has washers, premium blade steel, nice titanium scales, a great deep carry pocket clip and IMO it's cool that you don't see the spring at the back (the back of the handle is an actual spacer, the spring is hidden underneath it). Spring tension is rather low. What I didn't like about it is that it has the "half stop" not at 90° but at ~100°. That's an ocd problem / a nit pic of course but for me it was part of the reason why I let it go. The other reason was that I prefer the UK PKs FFG blade over the Zipslip's blade. That somehow sealed it's fate. I just felt like I wouldn't use it enough to justify keeping it. As long as you like the design and the blade it objectively is a great knife, especially when you consider it's price point, the materials, workmanship and the cool packaging (a really fancy paper box with a cool little fabric pouch in it). For me it was the knife that prooved that the Chinese are capable of building good knives.
The Böker XS OD is my least favorite knife on this list. It was rather cheap and I liked the stonewashed look. Build quality is okay. But the knife was a lot heavier than expected (full steel liners will do that...) and mine was so hard to open that it barely qualified as a OHO knife. I later on read that the reason for this is the stonewashed finish. Other XS with satin blade are said to be better to open. Might be an okayish budget choice then when you are looking for a slipjoint knife that can take a beating.
Last but not least: The Hinderer Slippy. The first one I had was a Slicer I bought in early 2018. It had tiny washers, a blade that had a bit play left and right and wasn't centered to 100% and weak spring. It was a great slicer and felt more like a "real" knife than the UKPK LW. OHO was okay. But all in all I was a bit disappointed considering the price point (paid almost 300€ for it!) and thus I send it back to the dealer.
Today I got my second Slippy. It's a 2019 with Spanto blade and I got it used (as new) for a good price. Blade centering is top notch, the washers are bigger and the Spanto blade is about as slicy as a Slicer blade but IMO looks cooler. So that's good. But the spring is stronger in comparison. It now has quite a bit of power, what makes it a bit hard to open with the thumbdisk and one hand. On the plus side: This one doesn't have a half stop. The spring will carry the blade to about 90°. Then there is a dead zone up until ~30°. At that point the spring will close the blade for you. I really like this kind of solution, because it will allow you to close the knife in a fluid motion whereas the UK PK (especially the Heinnie-Version) will stop the blade really hard at 90°.
Conclusion: All knives I listed are okay. Considering price and quality I'd absolutely recommend buying a Heinnie UK PK. The Kizer and the Hinderer are also fine choices though.
Some quick photos of my knives:
Heinnie UKPK / Terzuola (sold last week)
Heinnie UKPK/ Kizer Zipslip (sold today)
All my current Spyderco Slipjoints and my Hinderer Slippy Spanto
Please note: The knife above the Hinderer is a Spy-DK, I didn't mention it because it is two hand opening (if I had to mention it would be my least favorite - too much spring tension).
Also note that the Spy-DK and the Sprintrun-Urban have Cuscadi scales. The originally came with FRN scales as well. The PITS has been blue originally.
PS: As a guy that isn't free to carry whatever he wants I have to tell you that I wouldn't go for a OHO slipjoint if I didn't have to. Maybe take a look at the Spyderco Native or the new Para 3 LW. The compression lock is easy to unlock with the knife holding hand.
