Breaking edges

[sammer]

Just curious, does anyone else have a problem with edges breaking?
I've broken 3 so far trying to bend a tight radius at the tail.
2 were cold bent and one annealed.
Its really pissing me off.
Your just about there, one last little tweek, then snap.
The edges are from SBM but i think they are all the same (CDW?)

I'm thinking about putting a stainless tail protector in and ending my edges early.
It would save a lot of labour and probably give better protection to the tail.
I'll probably try aluminum first as I know how it bonds and its easier to cut and bend.
Stainless would definitely look better and offer better protection.

Anybody tried to bond stainless?
I used tip filler last time and it turned out OK, but gets eaten up pretty fast by the base grinding stone.

sam

[skidesmond]

I never had an edge break. Are you wrapping around the corners on the tail? That's a tight turn. I run my edges to end of the tail. I've thought about running the edges short of the end of the tail, maybe a 1/2 inch and fill the rest in w/ leftover ptex base material. I did that for the tip on the last pair of skis.

I did a 3/4 wrap and filled the rest in with PTEX base material and it sealed up nicely.

[sammer]

Yup, doing full wrap.
And until recently it hasn't been a problem.
I've bent edges for 6 pair without breaking one.
Seems they get work hardened from the initial bend.
or they are extra brittle?
One broke after I slightly over bent it and was bending it back.
but the others were just bending as usual.

I don't get it.

sam

[krp8128]

And until recently it hasn't been a problem.

sam

I noticed my last edge order from skibuilders had a different tab profile then what i was used to.

Different edges might mean different heat treating, so they are probably a bit more brittle then what you are used to bending. I don't see why you wouldn't anneal for a full wrap.

[knightsofnii]

.... because heat treating them like that totally changes their hardness. Does anyone ever re-heat-treat them to bring them back to their rockwell 48 or whatever the stock hardness is, after bending them right? I cant remember how that's done, tempering?

But possibly extreme bending could be heating or straining them too and changing that hardness?

But yea, ski corners are crazy for bends. Just quit, make snowboards!!!

Kidding, Full wrap rules but only if you can nail it. How bout pre-bent? Eh those never fit either.

I think we need to work on revolutionizing the way edges are built, applied, bent, etc.

I've snapped edges when trying to straighten out a bent edge by hand, but in our roller they're fine, but sb edges are far more mellow a bend than skis.

Hayes bros. used to use a plastic "tip protector". They would end the edge abruptly, the nose/tail were cut to a funky shape @ the end, and a thicker plastic was laid in, it was even too thick and had to be ground down flat with the base, there was a recess in the cassettes for this. But it worked real good! You could just get crown overstock at whatever thickness you think you need and use that instead of a metal tip protector

[krp8128]

.... because heat treating them like that totally changes their hardness. Does anyone ever re-heat-treat them to bring them back to their rockwell 48 or whatever the stock hardness is, after bending them right? I cant remember how that's done, tempering?

It kills the hardness, but do you really need it in the last inch or two as the edge curves around the tip? I would have to go double check my materials book, but IIRC heating to bright red and then submerging in oil should re-harden them.



I annealed my edges once, and found that the bent too easily, causing me to gets kinks and funky bends.

my $0.02

[knightsofnii]

me too, they get too soft. Then any rock dings or even resting them up against a wall having them resting on the ground, will dent them up, push them into the board, etc.

Yea I'm not really looking forward to busting out my ME-215 textbooks haha.

[sammer]

Well, I think I'm done trying to bend the tail radius.
I'd really like to try stainless and butt the edge up to that. Should be solid.
I'm definitely gonna use aluminum on the pair I'm working on.
I'll let you all know how that turns out in a few weeks.

I have annealed the tail bends most of the time but, it does bend kinda funny and I've broken annealed edge too.
The edges are from SBM and I've used the same batch for the last 5 pair, so I don't think its so much a material problem as user error.
They just aren't meant to bend that sharp.

Not bending the tails should save me a bunch of time.
edges are nowhere near as daunting now I have a new bender (thanks redbull and twizz)
I have to thank my machinist as well. He built three stainless rollers as per twizzstyles drawings, and a fancy handle, and only charged me three bottles of white wine

sam

[Alex13]

Annealing softens the material, not really desirable for ski/board edges, they plastically deform too easily and could have an adverse effect on hard usage (i.e. under board/ski flex, they bend and plastically deform instead of springing back).

To harden them again you need to reheat them to the austenizing temperature (700+ degrees C for steel) and quench in oil or water. This cools quickly and changes the crystal structure of the material to martensite. However, also makes them very brittle, so they wont bend but may snap on impact - also bad for the demanding effects of skis and boards.

Tempering is the way to go. You have to heat, then quench, then reheat to a lower temp (lower than you would anneal at). You'd usually temper to either 150-260 degrees C or 370-650 degrees C, 270-360 degrees C can result in brittling. This converts the crystal structure to a combination of ferrite and cementite which is very tough, not too brittle not too soft.

*edit* - you need to hold it at the tempering temperature for a few min, then cool slowly.

[Jekul]

Great discussion so far.

Here's a question I now have. What is the minimum bend radius for non-annealed edges? On the pair I'm currently working on I'm down to a 20mm bend radius without too much trouble. Has anyone else tried smaller than that?

[Alex13]

Its hard to say without knowing the ultimate tensile strength of the material. Anyone have any idea what that is?

[knightsofnii]

how about bending it in stages?
bend it to large radius, then again to a smaller one, etc, till you get the desired bend, that way you're not super stressing it all at once and causing it to heat and warp/crack. I cant be sure that would make a difference but give it a shot.

[doughboyshredder]

on alpine boards the manufacturer I used to work for would remove a tine to make that tight radius bend easier.