UKH

Hi,

Possibly a silly question.

I'm told the threads provide most of the holding power of a screw. 

Ice has different strengths at different depths, so why don't ice screws have threads extending their whole length?

This might help if the inner ice was less good, and reduce the need for removing screw then fumbling for a shorter screw?

The additional weight would be tiny. 

In reply to David Coley:

Surely the %age of "holding power" from the threads varies with the angle the screw is inserted, relative to the horizon?

E2A no treadmills here, the ice has frozen the axles

In reply to David Coley:

They do, or I guess one could say have existed. BD made some for Gadd's attempt at Helmcken Falls on natural gear:

youtube.com/watch?v=ydkJ1zG9r4c&

see about 1min in.

I'm wondering if the real world gains of a fully threadded screw are actually limited, as the end of the screw closest to the hanger is where ice gets crushed by a shock load. Thus I would imagine the threads here likely aren't really going to be doing much in terms of adding any extra strength or holding power, as the ice is gone.

Then I guess it's a case of the manufacturer thinking why machine something that gives you no advantage.

In a straight outwards pull they may add some holding power... maybe. 

In reply to David Coley:

The extra material in contact with the ice would mean that you have more resistance when screwing it in. 

My limited experience of ice climbing has been that the cruddy ice is on  the exterior normally so you hack through that to get the screw in in the first place.

In reply to David Coley:

Probably the same reason as the threads don’t project more, as you don’t need it and it would just add weight and make them harder to place. Screws fail in reasonable ice by pulling out a Chunk of ice. Longer screws will need to pull out a bigger chunk of ice. They also ofc often allow you to access the better quality deeper ice.

In reply to David Coley:

Unless you're on some overhanging ice then ice screws usually go in a bit steeper than horizontal (that's the theory anyway). When you land on them the screw flexes and shatters the ice at the surface (usually cruddy anyway, see above). 

If you look at some stubby's the thread usually goes all the way up to the hanger;

https://cdn11.bigcommerce.com/s-hgn1l9sh63/images/stencil/300w/products/114...

In reply to ColdWill: interestingly I’m sure the ‘guidance’ on the old petzl info sheets was to place screws at less than horizontal I.e. pointing up a bit. 
 

not being a pedant and whenever I place them it’s however my fear means they go in… up, down, straight  😂

I'm still not seeing why on a longer screw the threads stop half way. The additional weight in making them run the whole length seems very small. 

We have all drilled into ice which seems fine, then at depth softer stuff is meet. In extremis surely it would have been a great idea if we still had threads in the good stuff. 

In reply to David Coley:

Ease of screwing them in.

The resistance from the tip biting though the ice will be more or less constant as you get in deeper, but the friction between the ice and the surface of the threads will increase linearly as more turns enter the ice.

Thus, once you have enough turns to keep a longer screw from pulling out axially (which is not the main failure mode anyway), adding more turns will only rarely provide extra safety, but always extra hassle.

As someone pointed out above, this is why stubbies do have threads all the way.

CB

In reply to cb294:

Thanks.

How noticeable do you think that extra friction from more threads be? A big hassle, or only just noticeable? Ta

In reply to David Coley:

Not that hard I assume, fully threaded screws would probably also work.

I am not 100% sure, but didn't the old BD screws (before they got  the little foldable lever) have full length threads even in middle lengths?

CB

In reply to smithaldo:

That's what I meant to say. Pointing up a bit.

In reply to ColdWill:

In good ice, ice screws are stronger pointing up a bit with the hanger slightly lower than the teeth in the ice, that way the threads take more of the force and the screw is more in line with the force on it. Current petzl advice is to have a 90 degree angle (which sort of hedges your bets somewhat wrt ice quality / vs strength).

https://www.climbing.com/skills/learn-this-bomber-ice-anchors/

https://s3.amazonaws.com/Petzl_home_Prod/Accessbook/ACCESSBOOK-ICE-CLIMBING...

In reply to CurlyStevo:

tbh they go in any which way you can get them in.

In reply to David Coley:

This is only the case if the head is pointing down at a steep angle, otherwise shear force contributes quite a lot. When a horizontally-placed ice screw gets severely loaded, the ice near the hanger disintegrates first and the tube starts to bend downwards. Any thread on this section of tube will not add any holding power. As the ice continues to disintegrate and the tube continues to bend the threads on the far end of the screw start to play their role.

In compact ice it's actually better to have the screw pointing slightly down so that the volume of ice below the initial section of tube is greater. However, this assumes that the threaded section is in good ice. Unfortunately, on steep icefalls it's often impossible to know if there'll be an airpocket under the surface and so perpendicular to the ice is usually the best bet.

I'm guessing it's to do with them not serving any purpose in most instances, plus the fact they will increase friction when screwing them in.

I've heard that BD ice screws are very slightly wider at the teeth to lessen this friction as the screw sinks deeper. Can anyone confirm?

Grivel make their screws with the diagonal surface of the thread facing in the direction of pull so that the force is directed into the mass of ice rather than parallel to the shaft. Not sure why the other manufacturers haven't followed.

In reply to oureed:

”In compact ice it's actually better to have the screw pointing slightly down so that the volume of ice below the initial section of tube is greater.“

either that sounds wrong or I’m reading it wrong, can you provide a link please?

In reply to David Coley:

As a little update to my earlier post, I dropped Will a message (given that hes probably one of the few people on the planet to actually use a fully threaded modern screw) and his simple response was indeed that there is too much friction when turning them in.

So 10 points to Spenser and cb295!

Not going to lie tho, fully threaded screws do look kinda bæd æss (creds to weighmyrack for the pic).

I remember reading this a few years ago and being amazed that other manufacturers don't do the same. Seems like a great way to get more ice involved with the screw, with a really minimal change to the screw that doesn't seem to make any difference to ease of placement or any other negatives.

I wonder if it actually makes a noticeable difference. Don't suppose people really fall on screws enough for there to be much anecdotal evidence around.

In reply to CurlyStevo:

It's directly from a friend whose job is testing climbing equipment, so no link to hand I'm afraid. You can visualise it by drawing a vertical line to represent the surface of the ice and then slightly upward and downward lines to meet it - these represent the icescrews. With the upward pointing screw you'll notice that the triangle of ice beneath the tube has an acute angle to the surface of the ice. When you apply a downward force, this triangle of ice will shatter and the tube will start bending until it is eventually pulling downwards. With the downward pointing screw you'll see that the angle is obtuse and so will resist a much higher load (assuming that the threaded section is in hard and compact ice).

In reply to Fellover:

According to a Blue Ice video (with a former BD product designer) reverse threaded screws like those found on Grivel and Camp screws only show real increases in straight (outwards) pull out strength in the medium used to certify ice screws which is a form of cellular concrete. Apparently in actual ice the difference was negligible.

See 12:42 here: youtube.com/watch?v=CF-2ekq22y0&

In reply to GarethSL:

I had full thread steel screws back in the 90s, Cassin I think. But the tube was much thicker metal though than normal ones now, so they were a fight to get in any time, and almost impossible in dense new ice in Nordic cold temperatures. Don't know if the full thread added much to that.

Don't know what happened to them, come to think of it now... Must have sold them to some sucker* probably in Scotland on the basis that Scottish ice is normally slush puppy anyway.

*(Apologies if you remember buying funny Cassin screws off me 20 years ago)

In reply to GarethSL:

Thanks, interesting video. Suppose if the reverse thread doesn't make any difference in real ice then there's no point. Not sure there's any harm either though - he says it makes the initial bite worse, but I don't notice my grivel screws with the reverse thread biting any worse than my BD ones, I'm only a very casual ice climber though.

Separate rant:

He says they've done loads of testing on this, but I have to admit I don't like it when climbing companies say they've tested something extensively and just want me to believe it on their word. E.g. in this case I want to know stuff like; what sort of ice qualities did they test in, what angles of screw placement etc. It's mainly just to satisfy my own intrigue really, so I can't complain too much. I just find it frustrating that so much climbing gear research is hidden behind closed doors. Obviously they don't want to share research with their competitors, but I still get annoyed by it! It means that we, the end users, only have the knowledge that gear has passed the tests required by the standards, which are themselves hidden behind a paywall (grrr) and as he points out in the video not always even relevant - I'd much rather have a 10cm screw that's good for <10kN and uncertified, rather than no screw atall! We have to rely on people's anecdotal evidence and people like the HowNot2 guy who does useful but pretty random and not always particularly well setup tests on whatever he happens to fancy (not a criticism of the HowNot2 guy, he's a great source of info, he does what he wants and fair play to him, it's not his job to do exactly the tests I want him to do).

In reply to GarethSL:

As an aside I like the way Blue Ice are trying to do boundary pushing things with gear that other companies aren't doing so much. The superlight harness I have from them is great, when I got one it seemed to be the only superlight harness with actual gear loops, rather than just a ski racing harness with one floppy gear loop. More major brands seem to have followed suit now, so there's a bit more choice, don't think it would have happened so quickly without Blue Ice though.

In reply to David Coley:

Interesting thread - if you read Jim Titt's website the pull-out force for stakes and pitons is proportional to the difficulty of hammering them in - the friction is the same to pull out as it is to hammer in.  Failure is by the stake tipping over and eventually pulling out. I would assume an ice screw fails by a similar mechanism, or the ice fails.  Now a screw is different as the screwing in reduces the peak force required (inclined plane maths), however the screw thread increases the friction to remove the screw as it's not unscrewing to pull out. So, logically you would want as much friction as possible i.e. a full thread......but that's hard to screw in and I guess it's better to screw in a weaker screw to full depth in extemis than fail to screw in a stronger one.  Tapered barrels have been mentioned above to reduce that friction further, so logically, the ultimate screw would be fully threaded yet have a tapering barrel (narrower at handle end) to reduce screw in friction - only the front half touches the ice. When you weight it the barrel flexes and the threads then come into contact with the ice thus increasing the friction on the side being pulled against the ice, thus reducing the load on the deep threads.  You could even have the shallow threads being simple circumferential ribs rather than a thread.

In reply to Fellover:

A couple of things:

• PPE regs can make the sale of things quite restricted in the EU, hence the sale of "uncertified" equipment is difficult/impossible
• UIAA Standards are not behind a paywall. Though they are voluntary standards (unlike most EN/UKCA standards) and are currently intrinsically linked to the EN standards, the pictograms do give you a good idea of what's going on, e.g. https://theuiaa.org/wp-content/uploads/2021/12/UIAA151-Ice-Anchors-728x1024... and the rest are found here: https://theuiaa.org/safety/safety-standards

In reply to galpinos:

I'm sure. I don't know how hard it is for Blue Ice (they're Chamonix based right?) to release an uncertified ice screw, but I'm glad they're trying to/have. I can't work out if they actually sell the tiny orange handled one here https://uk.blueice.com/products/aero-ice-screw but it's not listed as meeting the relevant EN standard and the designer in the video linked above said it wouldn't.

Yeah, the UIAA pictograms being available is good and I appreciate it. Still annoys me that the UIAA pictograms say at the top that "For full details EN XXX should be consulted" though.

I just don't like standards not being freely and fully available - I trained as a structural engineer and it annoyed me then that standards aren't freely available. As an engineering student I was allowed to view the standards in the library, but (in theory) not allowed to photocopy or take photos to look at again later, ridiculous imo. It just seems outrageous to me, these standards are essentially the law - but I have to buy them to know what the law is! I know there are reasons for the paywalls, but I don't like it. Sorry to rant, it's just something that really annoys me.

In reply to Fellover:

I agree about access to standards. As an engineer, it drives me mad too.

In reply to GarethSL:

Hi

I also contacted Will Gadd.

I don't 100 percent buy the increase in friction thing being the killer. Might be in some ice, but in weaker ice or ice with weaker layers (the ice I'm targeting) , normal screws go it so very easily even doubling the friction wouldn't really be an issue. In fact in might feel comforting. If the ice on the route is expected to be good, leave the fully threaded screws in the car. If not, take 2, and if not needed, they can be your belay screws, where on most modest graded routes one would be in balance and the friction largely irrelevant. Although I'm very much not an ice, so maybe I've got this wrong? To me it is the same as my rack of RPs. If I'm on the North Coast of Devon I carry them. If I'm at stanage I don't. 

However Will also said to me that the market for screws is so very small having a second range of screws just wouldn't be worth it for a manufacturer. This sounds like the killer.

I watched a video by BD on making their screws and from what I can see fully threaded screws would not add anything to the process as it just means cutting less metal off. 

In reply to TobyA:

I remember using a couple of screws with a wider bore than normal back in the day. I felt like they were good for re-using other people's old screw holes because they still went in OK but maybe had more holding power thanks to the extra width. Well that was my theory - never tested. 

In reply to Dan Bailey - UKHillwalking.com:

I bet subsequent parties with normal diameter screws got well annoyed though! "Who's been using fat screws, I've got to drill my own now!"

In reply to Toerag:

And who has hacked the crux to pieces?

In reply to Toerag:

I do hope people DON'T use existing holes. I was told (by an Alpine Guide no less) that this was an unsafe practice - far more likely to be ripped out.

In reply to fred99:

Contrary to that, re-used ice screw holes have been shown to have a negligible difference in strength compared to a freshly placed screw and are almost as strong as a horizontal Abalakov. See this study here: https://alplager.kz/wp-content/uploads/2016/01/Ice-Climbing-Anchor-Strength...

The point being made above is that a wider screw going into an old hole is likely as strong as a freshly placed screw. So it largely comes down to what you have on your rack. Obviously a thinner screw in an old hole is naturally not going to be as strong.

The main argument for re-using a hole comes when climbing busy and well traveled routes that end up as Swiss cheese at popular belay points or at their crux. On pure ice routes this is probably mostly a North American/ Central Europe problem, tho I can imagine in Scotland where there isn't so much ice this issue may arise at belays that are a combination of err "stuff".

In reply to oureed:

either that sounds wrong or I’m reading it wrong, can you provide a link please?

Sorry I couldn't follow that and I have half a maths degree.

If you mean as per this article and they should point in an upward angle then yes you are correct https://www.climbing.com/skills/learn-this-bomber-ice-anchors/ (just using unusual terminology)

Surely though that would be a smaller volume of ice under the screw though?

In reply to CurlyStevo:

I think part of the problem is what he means by pointing upwards. Pointing the thread end upwards, ie the outer end downwards or the thread end downwards and the clipping end upwards.

Be specific.

In reply to David Coley:

Just to add a useful link to this thread, here's some testing by BD on the strength of protruding screws.

https://www.blackdiamondequipment.com/en_US/stories/experience-story-qc-lab...

In reply to GarethSL:

I think the issue of reusing old holes has got more complex, similar to the post above - of using higher diameter screws. There is now more use of wider diameter screws and variation in screw diameter with the wide spread use of alloy screws.

So, while reusing holes of the right diameter is safe there is a growing chance of a mismatch, of putting a steel screw into a hole bored by an alloy screw. I have no idea if this is always obvious or not.

In reply to CurlyStevo:

The angle of insertion was researched by Black Diamond quite a while back, although I can't find the original article. It is referenced in this paper: https://beverlymountainguides.com/wp-content/uploads/2016/02/Ice-Climbing-A...

"It is well understood that placement of an ice screw, whether in dynamic shock loading or slow pull testing, produces the strongest results when NOT placed in a negative angle (i.e., using the screw in a levering configuration). So, from somewhere between 0° and +20° is the ideal angle, and that was our target range for testing rebored screws."

In this case the positive angle is hanger below threads.

In reply to Wil Treasure:

Which is what the link I already posted says and is nothing new to me. I don't get how that can amount to the "volume of ice below the initial section of tube is greater“ which is why I questioned it. I think the use of obtuse and acute angles was ambiguous in the description too.

In reply to CurlyStevo:

You're right, the description is ambiguous, but there is a diagram on the BD QC lab about reboring screws, referencing this and clearly showing hanger below threads. I'm sure there was a QC lab about this as well, but the link in the other one goes to a dormant page on the Needlesports site.