UKH

My replacement ice picks came today.  Unfortunately the holes for the bolts are just too tight.  Instead of 8mm diameter they need to be enlarged to 8.3mm (approximately).

I'm not sending them back to Poland. Is it easy / possible / cheap to convert an 8mm diameter hole in 4mm thick steel to an 8.3mm diameter?

Do you have access to a bench drill? Much easier and less likely to go wrong than a hand drill. 8.3mm drill bits seem to be pretty cheap and I'd be tempted to get an 8.2 as well and try it with that first.

Every time I've used a drill the results have disappointed me.  Thanks for suggesting that it's possible to make the holes the right size.  ... now I need to find an expert driller.

What are the picks made of? If it's a standard tensile steel then you should be able to do it by climpling firmly to a drill press and doing it. If they are made from left over bits of russian tank you've got rought between bob hope and no hope unless you have a cnc mill with some sharp cutters...

It depends on what the steel is. Steel comes in two (broad) types, mild and carbon steel. Mild steel will be easy to drill carbon steel will be impossible. I'd give it a test with a file first (on mild the file will bite into the metal, on carbon it'll skate across the surface). 

Good questions: The bolt holes are for the bolts to attach the picks to the axe head.

Ill ask the supplier what metal the picks are made from.

Eh? Carbon steel is impossible to drill? Not really - it depends massively on the grade you're talking about as there's a lot of different grades in all sorts of different hardness states etc. - also we're not talking about a big difference in diameter. And literally not a single ice tool pick will be made of a low carbon steel like mild as it bends like a really bendy thing. The major difference as I said above will be if the picks been made from armour plate which will be incredibly hard. I'm pretty certain if it was a BD pick you'd be able to drill it with a drill press... If its armour plate pretty much your only possible course of action will be with a grinding stone on a dremel which will retemper he steel around the hole - if you did that you would have to keep the pick cold - i.e. dowsed in water very frequently to keep the temperature right down.

What you need is some Tungsten Carbide Drills, whatever they are:

youtube.com/watch?v=eoSeVEp-1OA&

Thanks for the painstaking research 

No problem.
My experience is that any hole can be made bigger with enough patience and lubrication...

Enlarging by .3mm you will only have to show it the tip of the drill with a bit of pressure and it will go through

Or the drill to catch and give you a horse's arse.

The picks will be made from hardened and tempered steel. I really, really wouldn't phuq about with the bit of the pick that holds it to the shaft.

What I don't get is why the holes are the wrong size. If you bought a replacement then it should be replaceable, full stop. Unless you're trying to mix and match I'd send the picks backs and ask for ones that fit the phuqing shafts thanks very much.

He said he didn't want to send them back, hence the suggestions he's getting.

I'm not even sure they will be hardened very much, they would snap the first time your put them anywhere near rock, tempered maybe.

Just buy a carbide bit or a reamer if he's that bothered, 0.3mm of material is nothing, the steel is only going to be effected if its heated, which it won't be to any degree opening up by that much

Have you ever worked in s machine shop?

Yes, why ?

As someone who used to deal with lots of small engineering businesses, whenever I had a metalwork issue I would ask them if they could do the job - and they inevitably would help or suggest someone who could. So look for local machine shops and get in touch.

UPDATE

Thanks to all who've suggested solutions.  I've learned a lot from you.

Today I had a reply from Kuźnia Szpeju.  The holes neeeded to be cleaned after the laser cut. It will be easy to clear them with an 8mm drill.  I will be able to test this next Friday when I have an appointment with a metalworker.

Um, if all else fails, you could try to get some marginally smaller bolts?

I am very glad you have sorted that out. Close-fitting bolt holes are pretty standard in these applications and the 8.3 is more like a standard clearance for a M8 bolt which is probably not appropriate here.

Next problem. Do you have a torque specification for these bolts and a method for measuring it?

Why 'problem'? I very much doubt there's tight margins on the torquing of pick bolts. People have been swapping picks for years without problems. As far as I known. 

1. Pick retaining bolts are, of necessity, short bolts. Short bolts provide a poor fixing and are not as resilient as long bolts. Short bolts are more likely to fail due to over-torque during tightening.

2. Insufficient tightening allows the pick to locate largely on the basis of a shear load on the bolt shafts and other location devices designed into the tool. This leads to movement, wear, loosening and early failure. 

If torque was that critical it would be marked on the head.

Just for fun have you worked out the shear load of an 8mm bolt, under and over torqued ?

I will bet it’s massivley in excess of that of an averagely loaded climber of approx 120kg hanging off them.....

That's a useful observation, Jim.  I've never changed picks before so I'm a *complete novice* at doing this, hence the elementary questions.  I used my miniature ice screw file to remove the remaining burs inside the bolt holes - and the bolts now fit!

The bolts are 8mm diameter 20mm long Allen bolts (I didn't know this 3 days ago) and are M8 according to a BSI standard.

As far as tightening them is concerned I'm inclined to Allen key them hand tight and then do one more quarter turn so my Edelrid Katana Pro tools do not suffer from the Nomic head wobble.

Hand (very) tight should be good enough. I’ve never had to use any kind of mechanical help - that would probably strip the threads.

The Nomic head wobble is nothing to do with how tight the bolts are. 

That just shouldn't happen. Burrs on bolt holes are shoddy manufacturing and there's no excuse for it.

All a bit qualitative and possibly academic. Do you have numbers?

1 (above) is very dependent on the bolt material and any compression built into the design (washers, head design etc.). Over torquing a M8 bolt in a properly designed head is very unlikely (in excess of 25-50 Nm) with a normal spanner-in-the-hand.

2 is also unlikely since a loose bolt will be obvious (rattling) long before real risk of failure. Again, assuming a decent design of pick-head fixing.

It's not as if using a torque wrench is going to help in practice (even if people have one). Outside of a lab or original production facility there's little correlation between bolt torque and clamping force - as soon as you get any dirt or corrosion on the pick, head, bolt or nut, all low-margin bets are off.

Like I said, people have been changing picks on axes ever since replaceable picks appeared. Hand tighten with a normal spanner (6-9") and check the head for loose bolts occasionally - it doesn't need to be any more complicated than that.

As for material for the picks, in the early days of Mountain Technology, the pick material for fully forged picks was the same alloy steel we used to use for crankshafts on turbocharged diesel truck engines. Quite good stuff! Whether such materials are available in sheet form to produce this product by laser cutting might be questionable in the UK but it might be available in other territories.

With respect to bolting, the minimum strength of socket screws is normally Grade 10.9 and many are Grade 12.9. The figures 10.9 mean 1000MPa ultimate and 90% of 1000MPa (900MPa) yield. Those number may vary slightly within tolerance band and according to the size of the bolt stock (size of raw material).

The tightening torque (torque wrench tightening) for a full depth 10.9 socket screw with a nut or tapped hole of similar strength would be around 33Nm. However, in the presence of an inferior nut, or if using button-head or countersink head screws, that might need to drop to 22Nm. (For 12.9, that would be 40Nm and 26Nm. However, some of the materials in the components you are clamping may not handle those forces. Some screw formats do not have the material marked on them.)

When two (?) M8 screws are torqued to 22Nm (the conservative option), the friction between dry clean steel clamped components would resist a force of over 8kN (0.8 tonne). This means no significant locating force bears on the fastener shaft or other locating features during normal use.

The balance here is between damaging the components from over-tightening and insufficient torque, and therefore clamping force, allowing movement and loosening, resulting in damage and possible operational failure.

Torques are for dry, clean, undamaged. If the socket screws are a standard size and format, there may be a local engineering hardware supplier who can sell you new ones.

All the above is good, but nothing there suggests that a hand-tighten-with-a-spanner-and-occasionally-check-for-loose-bolt methodology is inadequate. Assuming a well design axe of course. Correct?

As it exasperatingly states on my linkedin profile, "40 years of trying to teach the British how to use nuts and bolts."

The struggle continues.

Jim, why don't you give a simple answer to Marek's straightforward question?

Hand tightening is good enough, yes?

I reckon he’s probably got shares in a torque wrench manufacturer.....

As i said above, is it’s critical it will be marked on the head, but I can’t be bothered to dig mine out and check.

Thanks.

Thats good enough for me.

As one engineer to another: It's not enough to be right, you also have to be relevant. 

I do not think that Jim can give a simple answer, the problem is too complicated for that .

I once struggled to obtain a recommended  torque for bd vipers .  there must be a sweet spot between not coming loose and not over tightening.

If overtightened , the bolt has less strength available to resist the shear forces on it when the pick is loaded as it is already in tension .

I surmise that manufacturers do not bother to give a recommended torque as most climbers will be too cack handed to use the information.

Not the way this works. As tight as it will go without breaking during tightening is a well-established approach. However, that works less well with poorly designed bolted joints where you may get thread stripping or crushing of components. 

There is no factoring of the loads here except to allow for inaccuracies in the tightening method. 

Not convinced about that .

The way to get a handle on this is that every bolt is a spring (a very very stiff spring). The load on the pre-tensioned spring does not change until the pre-tension is exceeded. 

Still not convinced

Theory and actual may differ, need to do some testing.

What about yield point for starters ?

It turns out that tightening up to the yield strength is but one method used to apply the correct pre-load to a bolted joint. If I've read this piece correctly, Jim F is right: https://en.wikipedia.org/wiki/Bolted_joint

I don't understand what "tightening up to the yield strength means".  Neither can I explain "torque" or "shear".   Most of the explanation in the danm illustration goes over my head.  But I have the problem of needing to reattach new picks to my ice tools using M8 standard bolts.  As far as I can summarise the discussion on this :

1). If I over tighten the bolts then it could strip the threads.

2). If the bolts are insufficiently tight then the picks could work loose when 'loaded'.

3). If I fix the bolts hand tight then is this good enough?  The received answer seems to be that it's complicated ...  there isn't any communicable solution to the problem.

It's ok .  Under current conditions it's likely to be January 2020 before I can next use the ice tools - unless anyone has a simple answer to the question "how tight"?

I do not have a torque wrench to get that sweet spot exactly right (assuming there's no range of tolerance).

In the absense of being able to get a torque off bd , I used the very short bd  spanner to hand tight the bolts , then light tapping with a hammer until it stopped turning .

I reckoned that felt about correct and I could always use  a heavier tap if necessary to get them off.

This is after having to use every trick in the book  ( in a workshop with full toolkit and vice , not what you have on the hill )to get over tightened bolts off tools lent out.

People are over complicating this. Hand very tight should be sufficient - just use a solid Allen key and crank it as hard as you can. If you want, you can give it a tap with a hammer as Rick suggests but it shouldn’t really be necessary. Then keep an eye on it and check now and then.

I’ve swapped picks loads of times and never had an issue with Petz picks getting loose.

I did have BD Cobras go loose en route once but that was because I didn’t hand tighten them enough. Never happened again after took care to hand tighten them properly. Plus I think the bolts on the Cobras / Vipers aren’t as well designed - the bolt heads sit proud of the pick so are more susceptible to loosening.

Only a few people needlessly complicating this !

And to Pay Attention above, if anybody can strip an M8 bolt with an Allen key then they dont deserve to be using tools ! Just get them F tight, and F isn’t for fairly.....

Ha ha .  Thanks Richlan.   A bolting novice, I was surprised there's no simple answer to this, but if I don't have a torque wrench then it will have to be hand-tight plus, as Misha says.  

"40 years of trying to teach the British how to use nuts and bolts" .....  it's not nearly enough to induct me!

Just use a short Allen key and keep it square to the axis of the bolt.

Stop turning when blood starts to ooze between your fingers .

There *is* a simple answer: Do what countless people have been doing for decades with no problem - i.e., hand-tighten with vigour and then go and climb. The rest is just noise (in this context).

Unless of course you really *are* passionately interested in the minutiae of bolt mechanics in which case you can probably get a good education from people here. But it won't make any difference to your ability to climb ice. Safely.

I just go, as above, for as hand tight as I can with a tool comparable to those provided - (i.e. no 12 inch spanners) plus a splodge of loctite to prevent them coming undone of their own accord, which also stops any rust forming on the threads.   I always strip new tools down to put loctite on them, especially after once being unable to undo new bolts, deciding as a result that they they were tight enough, and finding out subsequently that this was not so.

All this tighting talk and  it’s not known  if the op has enlarged to 83  that’s only 1.5 a side. 

Lock tight. Or even a dab of nail varnish 

I am a huge fan of engineering adhesives. You are correct to point out that these can protect the threads from corrosion. In the past I have used low strength anaerobic adhesives from Loctite to perform this function in marine machinery without any significant locking and retaining effect.

It is important to realise that a cured anaerobic threadlocker is simply a sliver of acrylic ('Perspex'). It is not an alternative to proper tightening since it cannot survive the movement and forces within an improperly tightened joint. 

And you don't need to strip them down to do this. Simply apply Loctite 290, or other maker's equivalent, which is a very low viscosity adhesive that wicks its way into all the interstices of the assembled thread. 

[Other adhesive manufacturers are available.]

Good tip. If you have to disassemble/reassemble a joint afterward do you have to do anything exceptional to clean out the old adhesive?

Maybe not ''exceptional" but a fresh clean start, if achievable, is better for at least two reasons.

Each assembly event will tend to produce a slightly different joint shape and it is best if solid acrylic does not obstruct that.

The designed curing process normally requires contact with metals.