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Home Base Grinding, Anybody?

WhistlerGman

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Hello, I have 3 boys in alpine racing, each of whom has at least 3-6 pairs of skis. At the beginning of each season, I have them professional tuned, including base grind. Regrettably I am getting less and less satisfied with the work quality from a local ski shop. I suspect that young technicians only know which buttons to push the robotic Wintersteiger machine and pay less attention on quality control. So I am tempted to base grind the skis myself. Has anyone tried grinding the base using say a belt sander? It shouldn't be a rocket science, or am I missing something? Thank you.
 

Sibhusky

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I don't use a belt sander. I use the Skivisions tool. (https://www.tognar.com/ski-visions-ski-base-flattener-structure-tool/ or https://www.slidewright.com/skivisions-ski-base-flattener--structuring-tool.php) I usually do a couple swipes each time I tune, looking for areas in the base where the structure seems to be fading. Over time, this also helps keep the base flat. (I do my own sharpening as well, so my skis might never see a shop.) Once the bindings are mounted I MIGHT have them do the initial edge bevel set up, but not always. I really do not trust the shops to 1) do what I ask them to do and 2) refrain from doing stuff they think should be done in spite of the fact I didn't ask for it. I got sick of bringing things back. Plus just the hassle of dropping things off and coming back another day to pick them up, it's just easier to do it myself.

I think it takes a little bit to be comfortable using the structure tool. It's functional, but not pretty. But I don't care about pretty as much as I care about effective.

You can get different ruby stones with different grits. I use the medium all the time. Then I cut off the peaks formed by the structuring with a cutting tool. (Change those "mountain ranges" you just created into "plateaus') That helps with the glide. (More on the whole issue here.)

How to: https://www.slidewright.com/base-flattener-structuring-plane/
 
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Sibhusky

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By the way, @Jacques does something similar without the pricey holder. And he loves to create videos about it.

Also, I have to ask, what are you hoping to achieve with the base grind? Are you trying to get fresh structure? Or it just feels like you "should"? Every time you get a base grind you not only shorten the life of the ski, but you remove all that wax-saturated base you spent a season getting up to its potential, and you now have to start over, reconditioning your base. Each base grind, you sort of have to "recover" from with repeated ski/wax/ski/wax cycles.
 
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cantunamunch

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Has anyone tried grinding the base using say a belt sander? It shouldn't be a rocket science, or am I missing something? Thank you.

There is absolutely zero chance you will achieve truly flat with a belt sander.

Completely aside from big-picture questions like "What is flat - if it isn't a straight line average between the current height of the edges?" , any pressure you put on the belt will cause both elastic rebound inaccuracy (both from the base and from the belt/pulley system) and thermal (overheat) inaccuracy.

And that's just looking at the ski crosswise. There will be longitudinal humps and waves aplenty. And plastic hairs.
 

Philpug

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There is a reason that Montana, Rechmann and Wintersteiger tuning machines can cost $500k. But ... as good as these machines are, their limitations tend to be operator limitations.
 

justplanesteve

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There is absolutely zero chance you will achieve truly flat with a belt sander.

Completely aside from big-picture questions like "What is flat - if it isn't a straight line average between the current height of the edges?" , any pressure you put on the belt will cause both elastic rebound inaccuracy (both from the base and from the belt/pulley system) and thermal (overheat) inaccuracy.

The competitive side of me wants to take that bet, but i'm a ringer. & one of my larger machines has water coolant.
I can see making it work fairly well by adding end guide/supports, possibly a large radius (end to end) platen, using flood coolant, putting a VFD on it, and slowing the speed to a crawl while stroking the ski "with practiced skill" manually. Essentially an older version manual stone grinder.
Without practiced skill, you might loose a few skis dialing the speeds and motions in.

As has been pointed out, thermal issues are a very difficult factor. Metal and plastic expand differently.

The very first widebelt sander ("Planer" style/feed-through woodworking or metal conditioning machine) i ever saw arrived in a friend's shop in the mid 70's from some ski manufacturer. I suspect Head, as they had been local in Baltimore a few years before. Unlike actual woodworking widebelt machines, the belt was underneath the work, and the single top roll/feed roll was weighted, & rose & fell to accommodate variable thickness.

OTOH, back in those days, it seems many manufacturers' skis arrived railed due to somewhat similar base flattening ops. Where the conflict between multiple sources of differential expansion and differential response to any given abrasive is rife.

I have a shop full of abrasive machines, and prefer to just file and stone my skis as being faster, floor-to-floor.
When you get into race tuning, it is even more complex.
Could it be worth teaching the kids to maintain & tune their own skis with manual methods, like they had to learn in the old days?

smt
 
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justplanesteve

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Had no idea Wintersteiger was into multiple industries where high tuning can be a factor.

Separates seed, stick and biomass. The machine uses rubber paddles at high to low RPM toseparate seed and biomass through a sized concave screen. Air pulls allthreshed material to the next step where heavy seed collects in one bin, lightbiomass and Kief into another bin and stick and stem are ejected out of thefront of the machine. The process is so delicate on seed that lady bugsactually make it through this machine alive and well. Captures 100% of materialfrom input to output! One operator up to 300 LBS per hour.
 
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WhistlerGman

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By the way, @Jacques does something similar without the pricey holder. And he loves to create videos about it.

Also, I have to ask, what are you hoping to achieve with the base grind? Are you trying to get fresh structure? Or it just feels like you "should"? Every time you get a base grind you not only shorten the life of the ski, but you remove all that wax-saturated base you spent a season getting up to its potential, and you now have to start over, reconditioning your base. Each base grind, you sort of have to "recover" from with repeated ski/wax/ski/wax cycles.
I agree with you about the down side of grinding. However my boys are on the slopes 4 times a week for 16 weeks straight each season. Naturally towards the end of season, the skis are in rough shape and require reconditioning.
 

Sibhusky

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I agree with you about the down side of grinding. However my boys are on the slopes 4 times a week for 16 weeks straight each season. Naturally towards the end of season, the skis are in rough shape and require reconditioning.
Your "reconditioning" is presumably about the structure being worn off and the edges needing work. I do that all season long. My "reconditioning" is about getting the base well-saturated with wax after the base grind. Your coach is probably telling them to do 6 cycles to get them back in shape so they are fast, just like with new skis.
 

scott43

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By the way, @Jacques does something similar without the pricey holder. And he loves to create videos about it.

Also, I have to ask, what are you hoping to achieve with the base grind? Are you trying to get fresh structure? Or it just feels like you "should"? Every time you get a base grind you not only shorten the life of the ski, but you remove all that wax-saturated base you spent a season getting up to its potential, and you now have to start over, reconditioning your base. Each base grind, you sort of have to "recover" from with repeated ski/wax/ski/wax cycles.
I have a pro tuning book around that says the best way to ruin a ski is to auto base grind it... It's probably not that simple but yes, it's a job to be thought about..
 

Wilhelmson

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For a race ski where you want consistent base edge and a quality structure, I don’t see how a busy parent could accomplish this dyi.

Maybe this should be more about how to touch up the base edge with a stone and freshen the base with a cleaning cycle. That sounds doable. If they are railed well it’s a grind or a new ski.
 

Scruffy

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I have a pro tuning book around that says the best way to ruin a ski is to auto base grind it... It's probably not that simple but yes, it's a job to be thought about..
what is auto base grind?
 

scott43

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For a race ski where you want consistent base edge and a quality structure, I don’t see how a busy parent could accomplish this dyi.

Maybe this should be more about how to touch up the base edge with a stone and freshen the base with a cleaning cycle. That sounds doable. If they are railed well it’s a grind or a new ski.
I don't have time to wax them...
 

Scruffy

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There comes a time when you have to flatten a ski. You can be a wizard at tuning your edges, but the friction on granular snow will at least eventually create a long bevel, or your base side edge will be so chewed up if you hit any rocks/stones -even on protected race skis- that a base flattening is the only way to restore the ski to a level of performance commensurate to racing. A stone grind at a good shop is the most expedient, and usually the precise, way to do it. If you use the skivissions base flattener often, as per @Sibhusky, you can keep them flat, but the structure would not be race quality.

Now that we have home/DIY edge tuners, ala Razor's Edge, and et al, how long will it be before some manufacturer creates an acceptable home base grinder?
 

Wilhelmson

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I don't have time to wax them...
Time to admit I have been working down the last bit of wax I have left, and got a full tune on my newer skis up at Sugarloaf. They are pretty sweet now, but I did ski the crap out of the factory base.
 

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