Edge sharpening. Am I doing something wrong?

A snowHead

I've just been servicing some 2nd hand twin tips that we bought for peanuts for our youngest kid. I reset the edges to 2 degrees, checking I'd taken enough metal off by using marker pen first, diamond filed them afterwards and then used a gummi to remove burrs. They look loads better, but I'm wondering if I'm doing something wrong because although the edges now feel nice and smooth, they don't feel sharp at all. I'm wondering if I need a new diamond file as mine seems a bit clogged up and smooth now.

Also, I haven't done the base edge as I only have a side edge tool at the moment. Might that be a factor????

Cheers.

A snowHead

If you run the flat of your finger nail across the edge does it shave a tiny bit off? That is the usual test.
Side edge only should be fine, especially as you presumably use the gummi on the other face.
By 2º I assume you mean 2º less than 90º

Not that I'm an expert.

Well, the person's real but it's just a made up name, see?

A friend attacks his base edge like a dervisher freehand for racing on plastic, having borrowed them for snow they hook like a Fitzwilliam so side edge possibly enough for free ski.

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Snowball, Yes I only run the gummi flat across the base, covering the base edge as sharpening the side edge should raise a burr over the base. I can't seem to cut my finger nail though, as said, they're lovely and smooth now but I don't know if they're sharp as they dont feel sharp.

Anyway, snowHeads is much more fun if you do.

The super sharp feeling fingernail thing only indicates a hanging burr, smooth is good. Also, you should ideally have more than one grade of diamond stone, probably 100 and 400 as a minimum but preferably more. If your diamond stone is clogged up spray some cutting fluid (you were using some weren't you?) on and use a wire brush to unclog.

Leave the base edge well alone unless you get the skis base ground in which case you need to reset the base edge angle and start everything all over again. Taking material off the base edge you will make the ski base high and it will ski badly, all sharpening is done on the side edge. Base edge angle is veeeery critical.

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Cheers Narc,

My diamond stone is a medium so probably somewhere around 200 grit. I don't use cutting fluid but wet it thoroughly before putting it in the edge tool then also add spit to it. Seems to work and doesn't dry out..

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shootingmike, removing burr is done with diamond not with gummi stone. With gummi stone you remove whole lot of sharpness so that's probably reason, why they don't feel sharp.
As far as several dimanonds go... if you are not racing and catching every 0.01sec, don't bother. Diamonds are used for two things... one is to polish edge to make it faster (more or less noone is doing it even in World cup), and second, to remove burr. But that means you "drive" diamond once or twice over each edge (side and base) freehand without any guide or anything and that's it. Personally I use 400 diamond for this, and it works nicely. If you would want to bother with polishing, then you start with 400, and finish with 800 or even 1000.
Otherwise I agree with narc, that base edge is the one that matters for skiing. Side edge is pretty much same no matter if it's 2, 3, or 6 degrees (unless you ski on injected courses), but base edge matters. Problem is, that most of skis I have seen come with 0 degree base edge out of factory, and most of ski services don't bother setting edges either, so they are 0/0. And 0 degree base edge is dangerous, especially for Sunday skiers.

After all it is free

Unless you really want to slice your hands or gloves open each time you pick up your skis, the gummi is supposed to take the sharpness off without affecting the ability to ski, a single pass down held at 45 deg should do the job.

shootingmike, I didn't mean you to cut your nail (ie pass nail along the edge)- I mean to pass the nail across it, like when scraping off wax.

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Sounds like they may have been left "very" blunt in the first place, I'd bet that although you've taken the pen mark off the whole edge width, you may not have gone far enough beyond the rounded blunt point, a good reason for sharpening skis "little & often"

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That's another thing. The gummi stone bit, some sources say run it down the edge at 45 degrees, some say run it flat against the base. I've had another look at my diamond file again today and its definately seen better days, so I'll invest in a new one. Good point about maybe I haven't gone past the rounded blunt edge.. I hadn't thought of that, but I did take a fair bit off as I was conscious the previous owner might not have been so thorough.,

45 degrees for detune, flat to base "edge angle" for removing hanging burr. As above very fine diamond is good for de-burr.

You know it makes sense.

The other reason for "not very sharp" is completely wrong angle. You might be doing it with 2 degrees file holder, but without getting rid of (enough) sidewall, your angle was everything but 2 deg. And considering price of good sidewall cutter is 100+eur, that's normally last thing people buy, if they ever even do buy it.

Otherwise you'll just go on seeing the one name:

Possibly primoz, but I put marker pen down the edge before hand and it seemed to remove it quite evenly when filing....

Thanks for that tip gatecrasher, I'll stick to running it flat over the base then.

A snowHead

A snowHead

shootingmike, forgive me if you've already been there/done that but this might be useful. It's spyderjon's guide to tuning.

Well, the person's real but it's just a made up name, see?

Gummi is for removing hanging burr, pass at 45 degrees gently once is all it takes, Burr will ski off quickly but they will be grabby and cut your hand/gloves easily till it goes

Diamond files should be used with an angle guide, anyone claiming to handhold a constant fixed angle is deluding themselves

I agree base angle is most important but side angle a close second, the combination of both is what sets how sharp they seem

Sharpening the base will not lower the edges unless you go at it like a bull in a china shop and its easy to use a base scraper to flatten bases again, you are polishing an already set edge up, not grinding anything away. I have one set of skis that have been serviced around 100 times now (base edge) and have never been ground and the base is still flat (except at the tail, but many old Atomics are designed to be concave there)

Most consumer bases come from factory with a 1 Degree base and a 2/88 or 3/87 degree side angle

Get yourself over to Jons Ski tuning for gear and lessons. His site is a mine of information including factory edge angles. I'm an ex graduate of his and now do tuning commercially on a small scale

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I made my own sidewall cutter out of a piece of aluminum angle and an index lathe tool bit, works a treat saves a lot of time and bug9ering all my files.

Anyway, snowHeads is much more fun if you do.

Sidewall cutters available from Jon for a LOT less than the figure above

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Little miss Spock, thanks, read all of jons guide a while ago... I'm sure he'll be along soon as someone said above.

Thanks for the useful discussion though folks, it's appreciated. Sounds like I've done a decent job, it's just they felt smooth and not sharp..

Then you can post your own questions or snow reports...

After all it is free

Surely if there is a burr then you have cut right too the edge otherwise it would be round, you then remove the burr with the gummi.

All atomic factory skis come with 1,3. I've never seen any make come into my workshop with 0,0 (except race ski's and those that have just been ground). Here a list of the Factory Spec angles that the ski manufacturers set new non race skis to
http://www.jonsskituning.co.uk/content/view/31/41/

My sidecutter has a metal body and cost £30, has worked fine for last 5 years on all sorts of sidewalls, I've no plans to spend more on another

Oh well my customers will be pleased to know their skis have the same base and side angle all the way along (whatever setting they ask for). I can feel the difference in my skis grip after 3 days without a tune and I'm just polishing using diamonds (if the snow is firm or ice), that's a fraction of a degree change in reality. If I can feel that difference I'm sure a World cup skier will be affected by slight changes in angle along the length of an edge and we know that's true as some like the ends detuned. That detune angle will be less than the inaccuracies of hand holding. On injected hard ice that consistency becomes more important. Now I know why World Cup skiers sometimes seem to have days where they just seem off

Primoz, it just looks like we will agree to disagree. But I'm amazed that at top level tuning they would risk any inconsistency in ski prep. These are the people that change wax formulations for small changes in temperature and spend hours brushing bases for a minute percentage point of extra speed. I kind of assumed they all used the electric edge setters for speed as they didn't need to worry about ski life

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Nobody mentioned rule 33 ?

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duc996bp, it is possible to create a hanging burr on blunt skis with aggressive files, the ski feels sharp in use but the sharpness goes off much quicker, on my plastic slope skis I use the little hand ceramic edgers which actually puts a very hard intentional hanging burr on the edge, you can actually make a very blunt ski feel very sharp with only a few passes, the ski is still blunt but the burr makes it behave like a sharp ski that hasn't been de-burred.

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There's actually two methods for removing the hanging burr which is why there are some conflicting opinions:

Method 1 (Basic method) - use a hard gummi stone held flat on the base of the ski - do not try to angle the gummi to the base edge angle. Note that a HARD grade gummi must be used as a soft or medium grade gummi will (as Primoz says above) 'bleed' over the junction of the base/side edge & actually blunt it. A hard grade gummi, when held flat on the base of the ski, has just enough 'give' in it to 'mould' on to the base edge angle to remove the hanging burr but is not so soft as to bleed any further over to cause harm. Excellent results are easily achieved providing the hard gummi is held flat on the p-tex base & not angled on the the base edge angle so it's a pretty idiot proof solution & which is why I have it detailed on my website.

Method 2 (Advanced method) - use a diamond file (usually 600grit) or an Arkansas stone, held flat on the base edge angle to remove the hanging burr. This will then throw up some further extremely fine burrs which (as Ham says above) are then removed by single pass with a gummi held at 45 degrees to the ski base. Note that absolutely NO pressure whatsoever must be applied to the gummi otherwise the edge will be blunted. Hold the gummi very lightly between index finger/thumb & then sit it on the edge under it's own weight without any downward pressure. This method will theoretically get the best result but if any kind of pressure is applied to the gummi then all your hard work will be undone & you'd have been better off using the basic method. This is not the solution to use if you're a klutz with tools!

On my tuning lessons I always cover the basic method but I'm selective about showing the advanced method depending upon the student's ability with the tools & the level of performance they require, ie the advanced method for racers etc.

You know it makes sense.

Nice one Jon, thanks for clearing it up.. Just one quick question, using the basic method, how much pressure should be applied and I take it just one pass is sufficient?

Cheers.

Otherwise you'll just go on seeing the one name:

Just moved this to the equipment section

A snowHead

shootingmike, I've just re-read your initial post & I think you might be missing something with your use of your metal file.

The six million dollar question for side edge tuning is "how does one know how much to file?". The marker pen method is great for truing up an edge or if altering the side edge angle etc but if you have a 2 degree side edge angle with a 2 degree guide then your metal file will take all the pen off (or almost all it) on the first pass which makes you think that you've filed enough when it's unlikely that you have. The answer to the question is that you file until you can just feel the start of the hanging burr when you gently pull your fingers across the edge towards you - it'll feel rough & will drag on your skin.

And it could take take one pass of the file or many until you can feel the hanging burr. Then a wet diamond file(s) is used to polish up the edge or, to be more precise, to remove the striations left on the edge from the metal file as any high spots are unsupported by metal either side so they will burr over in use sooner - therefore the smoother/more polished the edge the more durable it is. Many people mistake the rough/aggressive feeling of the hanging burr for the edge being sharp as that's how they think a 'sharp' should feel when in fact a smooth burr free edge is what is actually sharp. It's a subtle feeling that's very hard to describe in writing or seen on a video but when I demo it during my lessons the two are then instantly distinguishable.

To remove the hanging burr with the basic method you'll need to rub with what I'd describe as a medium firm pressure - either in one continuous pass or in short back'n'forth rubs along the ski. Do one length of the ski then check to see that the hanging burr is now gone, ie there's no longer any dragging on your skin & you can only feel 'smooooth'. If not, then do another pass & retest etc. The finger nail test can then be done but be aware that any hanging burr present will also do a good job of shaving off your nail which can be misleading.

A snowHead

Thanks Jon, I'm pretty sure I removed enough metal as it took a few passes of overlapping strokes to remove all the pen, probably because they weren't 2 degrees to start with..
Thanks for the advice on gummi pressure, I do think I need a new diamond file though as mine was only cheap and now feels pretty smooth and clogged up.

Well, the person's real but it's just a made up name, see?

shootingmike, if by chance they were originally less than 2 degrees, you'd have to take quite a bit more edge off beyond the pen mark to get to the lowest point on the base edge, especially if very blunt.

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shootingmike, you've only taken off enough metal when you can feel the start of the hanging burr.

Anyway, snowHeads is much more fun if you do.

I could be wrong but seems to me that when I use newish files and take light passes from medium to a fine file I get very little hanging burr. I get very little and it seems to vary very much by how "sharp" the file is... I knackered a few files when first learning to tune by not deburring and removing rock hits and case hardening before using files. Now I have a set of very sharp files which work great... I also think most people dont take enough off with files and end up with a smooth dull edge after using diamonds...

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skimottaret, correct on all counts Cool

Then you can post your own questions or snow reports...

A lot of the time a ski will 'feel' sharper due to the slight burr, once it is polished the sensation when you run your fingere down is lessened as you are not getting the saw effect Laughing

After all it is free

Thread resurrection...

I smell spam...

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@kitenski, Spam can be useful to remove a hanging burr but be careful not to cut through it and into your fingers.

Help!!

Edge sharpening. Am I doing something wrong?

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