Ice screw thread direction

[Kevin_Matlock]

Another post regarding ice screws got me thinking about a question I've had for a while now.

 

A few years ago I bought some Russian Titaniums and they have the threads cut "backwards".

This was intentional, or so they claim, and was suppose to be some greatest-thing-since-sliced-bread sort of deal, but I have never seen this on any main stream screw before. I can only think that the bevel was cut reversed to allow for easier placement.

 

Consider my funky drawing -

 

Notice how with my Rusky screws ("A") the thread's sloped face points towards the hanger. To me this seems like they would pull out much easier than a nromal screw ("B") where you would have the resistance of the perpendicular cut threads holding against the ice.

 

Am I wrong here? Anybody see this type of cut before? Did I buy some F'd up seconds that claim to be the second coming?

Have never fallen on them to know if they would hold a whipper or not; anybody want to volunteer to be a crash test dummy?

[Fromage]

Grivel also makes their screws' threads like in figure A. Their reasoning is that by applying the load on the hypotenuse of the triangle the force is distributed over a greater surface area and thus reduces the chance of pulling out the screw.

 

Grivel's screws are awesome. Irbis Titaniums (the Russian screws you mention) suck big time. Nothing personal, but compare the

 

- # of teeth (Irbis = 3, everyone else = 4)

- diameter of the screw (Irbis < everyone else)

- thread relief, i.e. how much the threads stick out from the tube of the screw (Irbis < everyone else)

- screw length (I think Irbis are <16cm)

 

I used to have one of these Russian Death Screws and finally got rid of it before it got rid of me. Not only are they frustratingly difficult to place in hard water ice, they are jing of the first order. If I were you I would worry much more about the overall quality of this screw than the direction the thread bevel faces.

 

Righty tighty, lefty loosey.

[Mark_Husbands]

i thought this was going to be a plea for screws for lefties.

[Kevin_Matlock]

Grivel also makes their screws' threads like in figure A. Their reasoning is that by applying the load on the hypotenuse of the triangle the force is distributed over a greater surface area and thus reduces the chance of pulling out the screw.

 

Grivel's screws are awesome. Irbis Titaniums (the Russian screws you mention) suck big time. Nothing personal, but compare the

 

- # of teeth (Irbis = 3, everyone else = 4)

- diameter of the screw (Irbis < everyone else)

- thread relief, i.e. how much the threads stick out from the tube of the screw (Irbis < everyone else)

- screw length (I think Irbis are <16cm)

 

I used to have one of these Russian Death Screws and finally got rid of it before it got rid of me. Not only are they frustratingly difficult to place in hard water ice, they are jing of the first order. If I were you I would worry much more about the overall quality of this screw than the direction the thread bevel faces.

 

Righty tighty, lefty loosey.

 

Good info and not taking it personal.

 

The ones I have aren't Irbis though, mine are Uralsport and they aren't as shitty as my shitty leavers by comparison. They place well enough and have a slight outward taper on the inside diamater so they tend to be clog-resistent.

 

My only real gripe is comparing it to a BD screw I have it's pretty easy to tell which one would last longer (BD steel!). But I hear ya calling them a death screw; no way to exactly guarantee their quality control.

 

When I get a chance, I'll post some pics of the Uralsport screws for comparison.

[blueserac]

Well, your querry says it all; your answer is in your question. If you feel that your Soviet kit is funky, then place your chips on the marker that says it is. Black Diamond is the standard that the rest measure to.

 

Is you life worth the budget savings of a most likeliy more costly screw; and a wire is a lot less heavy than a screw for an Abalokov.

[G-spotter]

irbis screws are really nice for carrying on those days when you never use a screw

[montypiton]

the question on thread profile is best answered by reviewing a bit of history vis-a-vis ice screw design. fifty years ago, tubular screws were designed with threads having a "rectangular" profile with thread faces roughly perpendicular to the screw shaft. The thinking was that this profile would resist pull-out best. While pull-out resistance was ok, later engineers discovered that the most significant determinant of holding power for ice-screws is surface area - because the screw freezes in place, so greater surface-area yields greater freeze-bond. Any fracturing around the screw reduces quality of the freeze-bond. For these reasons, modern ice-screw manufactures increased the diameter of the tubular shaft, and machined a parabolic thread-profile on their screws (BD, OP, Grivel,Petzel). The larger internal diameter yields more surface area to freeze in, and the parabolic thread profile reduces fracturing during placement, as well as offering a slight gain in surface-area for bonding. This is also why the modern recommendation is to place the screw sloping slightly UP into the ice, instead of slightly DOWN as in the old days. While it seems counterintuitive, the up-sloping placement greatly reduces fracturing around the screw when it's loaded suddenly, thus increasing the overall holding power of the placement.

 

So- overall, your Russian screws are probably fine. When we first started seeing Titanium screws from Russia back in the '80s, everybody mostly loved 'em, and I still use mine from that era. They don't place quite as easily as the latest versions from BD-OP-Grivel-Petzel, but they're certainly functional - truth is, I don't really notice the difference that much unless the climb is extremely steep/strenuous (V and harder).