Kuzmin scraping and structure

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Blah
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Re: Kuzmin scraping and structure

Postby Blah » Tue Dec 16, 2014 8:30 pm

Loran wrote:As a matter of fact measured by Kuzmin, a (sharp) steel scrapper will render a much cleaner and better gliding surface than a stone-grind which leaves plenty of hairs and roughness. A stone-ground ski must be either be waxed or "shaved" to glide correctly.

Steel scrapping will actually be a post-processing to shave and decrease roughness of a stone-grind process.
The skis he tested had been ground by Lars Svensson.

At least greyish areas on my ski bases are gone. Forever.

After Kuzmin measured that fact, the stone-grinding process has maybe increased in quality, though.
Yet the very process of (relatively) high speed rotating emery stone has not changed, so the physical effect of creating hairs because of the tensile strenght of UHMWPE is still there.

Beside hairs and roughness, Kuzmin then questioned the kind of grind done by a rotating stone. Which is *always* small and straight patterns. They can be a dirt magnet, especially if you put in there soft wax acting as a " bond" for fluoros. When fluoros are gone, you're left with that " glue" inside the structure. Hence his research to produce different structure generating aeration without the adverse effect of collecting dirt. (Xriller). At the World Cup, they don't care much on that, as stated by Knut Nystad, because they are allowed to swap skis... (Every 8km for a 50km event).
Last edited by Blah on Tue Dec 16, 2014 10:19 pm, edited 1 time in total.

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Re: Kuzmin scraping and structure

Postby Blah » Tue Dec 16, 2014 8:31 pm

osloskier wrote:"Scraper" is a misnomer, I think. They don't scrape, they cut, and the result is better than with sandpaper. They are not just used for skis: http://www.stewmac.com/How-To/Online_Re ... shing.html


No, I get exactly what they are.

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Re: Kuzmin scraping and structure

Postby osloskier » Wed Dec 17, 2014 3:14 am

m2qItMot wrote:So, regarding the brushing after steel scraping - what exactly does it achieve?

How bad is it, if one does not brush or brushes not much?

How do you know when you are done brushing - just by the shiny finish on the base?

Last, but not least, can one use a cheaper (well ... er, previously purchased :-)) nylon roto brush? E.g. the Swix fine blue nylon one? Or the apparently discontinued, stiffer, less fine, black nylon brush?


It's hard to be sure exactly what's going on without a microscope. However, I think what happens is that the brush rounds and smooths the sharp peaks and valleys left by the scraper. Kuzmin recommends not brushing too much for wet snow as brushing reduces hydrophobicity somewhat. I have only noticed that brushing seems to have less effect in transformed or wet snow. For cold, fine grained snow and falling snow it makes a big difference. You will not have completely useless skis like an unwaxed, freshly stone ground ski, but they will be noticeably slower.

You don't really know when you're done except by experience. The ski becomes shiny before you're done. I'm sure you can use any brush you might have. I would stay away from steel, but maybe my steel brush is too sharp and other steel brushes work, I don't know.

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Re: Kuzmin scraping and structure

Postby osloskier » Wed Dec 17, 2014 5:15 pm

This thread needs some pictures, I think. Click images to zoom.

Kuzmin structure:

Image

Same structure, polished with high speed brush and hand brush.

Image

Structure for wet snow added:

Image

Tools used:

Image

This one is interesting. When I was going to refresh the structure of these skis, I discovered that there was some stone ground structure remaining at the tip. The tip is difficult to scrape and it's easy to overlook a small spot of ground structure if you don't view it in good light from just the right angle. Note how much more grey and worn the stone ground spot looks compared to the rest - even though the tip hardly touches the snow! I use these skate skis for soft or wet conditions when kick wax is difficult, so they have seen quite a bit of newly fallen snow, but I still think it's impressive.

Image
Last edited by osloskier on Thu Dec 18, 2014 2:40 pm, edited 3 times in total.

m2qItMot
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Re: Kuzmin scraping and structure

Postby m2qItMot » Wed Dec 17, 2014 5:26 pm

This is far above my grade! We are talking real art here :-) Thanks for the pics - they look fantastic!

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Re: Kuzmin scraping and structure

Postby Blah » Wed Dec 17, 2014 6:10 pm

Nice pics. I looked at the Kuzmin facebook page last night for awhile. That guy must scour the web constantly. He cited a discussion on Fasterskier and several times ripped Caldwell's posts. I had no problem with him doing this, but I was surprised to see him paying close attention to the US market like that.

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Re: Kuzmin scraping and structure

Postby osloskier » Thu Dec 18, 2014 12:44 pm

Thanks :)

The prepping was easier than photographing the result... glossy black is a challenge.

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Re: Kuzmin scraping and structure

Postby Loran » Thu Dec 18, 2014 1:04 pm

When You have a site/blog, referrers are tracked, most of the time

For instance, if you click on that link http://simplyglide.wordpress.com/ I will know that it comes from that thread.

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Re: Kuzmin scraping and structure

Postby osloskier » Mon Feb 16, 2015 3:46 am

JeffOYB:

The scraper lasts for many treatments.

Scraping away a stone grind is a lot of work and causes about 10 times as much wear as freshening up a ski that is already "Kuzminized". Each of the four edges will last for about two stone ground skis, but tens of re-scrapings. It's possible one might save on the scrapers by sanding away the stone ground structure first, but I've never tried that.

The whole point of scraping is that each treatment seems to last almost forever. I re-scrape to get rid of scratches long before the ski base starts to turn grey. Each scraping lasts for hundreds of kilometers.

You can also treat the Kuzmin tool as purely a structure tool and wax normally. How often do you re-grind your skis? Do you have some nasty scratches that you just ignore? Or maybe your ski bases aren't entirely flat anymore? If so, you can fix your skis at home by scraping and then keep waxing if you want to. I have tested waxing Kuzminized skis with CH + HF + HVC, and that worked like a charm.

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Re: Kuzmin scraping and structure

Postby JeffOYB » Mon Feb 16, 2015 7:05 am

thx!
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Re: Kuzmin scraping and structure

Postby m2qItMot » Tue Feb 17, 2015 9:58 am

How about "pre-scraping" with a regular steel scraper, after a stone grind? Just to get rid of the abrasive particles. Then you use the Kuzmin scraper. Has this been tried?

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Re: Kuzmin scraping and structure

Postby osloskier » Tue Feb 17, 2015 12:07 pm

I have tried that, but my other steel scraper wasn't sharp or stiff enough. It would have taken forever. This was the standard Swix steel scraper. I scrape the sanded grip zone with the dullest edge first to try to remove any abrasive particles, though. Perhaps one should scrub with some soap and water and a stiff brush first.

I have always tried out the factory grind for a while before scraping, so I think most abrasive particles would have been removed by skiing and a few waxings. But who knows.

I have bought my second universal scraper now after three or four years. I'm planning to sharpen the old, dull one with a diamond file and use it for the initial scraping. This would also be possible with a single scraper, dedicate two edges for initial scrapings and the two on the opposite side for re-scraping. Then you can sharpen one side yourself when it becomes dull. I will report how this works after I've tried it.

It should be relatively easy to make a sharp scraper out of a rectangular piece of hardened tool steel a few mm thick. The edges would be 90 degrees, though. The edges of the Kuzmin tool are slightly more acute, maybe 75 degrees or so. I don't know how a 90 degree edge would behave in comparison.

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Re: Kuzmin scraping and structure

Postby osloskier » Fri Feb 20, 2015 5:15 pm

I have sharpened my old, dull Universal scraper and am currently using it to scrape away the factory grind on a pair of skis.

It was fairly easy to sharpen. I put a diamond file flat on the table and placed the scraper standing vertically on its long side on top of the file, with the long side of the scraper parallel to the file. Then I rubbed it back and forth parallel to the long side. I have a hand vice, which makes it easier to keep the scraper at 90 degrees to the file.

It became very sharp and is removing material at an acceptable rate. However, the structure it leaves seems to be finer now. Not a problem, I can adjust it afterwards.

I now have a scraper of another, different coarseness. I'm not sure how it compares to the cold scraper yet, but I think it might be even finer. That would be nice.

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Re: Kuzmin scraping and structure

Postby m2qItMot » Sat Feb 20, 2016 9:19 pm

Has anyone tried the new "017" series of Kuzmin scrapers. The two-piece ones, where the blade and the holder are separate?

If so, any comments? How do they compare to the old ones? How easy/possible is it to sharpen them?

It also seems to me from the pics, that the direction of cutting is such that the blade is not supported by the holder, but rather by the single bolt in the center. I am a bit surprised by that - does the blade not flex a little bit?

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Re: Kuzmin scraping and structure

Postby JeffOYB » Sun Feb 21, 2016 1:03 pm

Seeing this mention of resharpening a Kuzmin makes me wonder if I could just sharpen my own steel bar well enough to do Kuzmin quality base prep.

I put emery cloth on a pane of glass then stand up a bar on it and support the bar with a wider block of true-angle steel. My shaver doesn't move but is polished. Then I polish/sharpen the other surface and end up with a well honed 90 deg angle.

Is 90 deg OK?

I notice mention that the resharpened scraper left a FINER structure than the official Kuzmin. ...One could just rill afterward, right?
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