8 degree base bevel

[KingGrump]

What are you using a ton of granite for?

A true bar. Doh.

 

[oldschoolskier]

Seriously, not for the skis. Use it to set up tooling and such. Occasionally if needed a true bar.

The accuracy is about 0.0002” over the entire surface for flatness. Its neat sliding 1,2,3 blocks like an air-hockey puck but no air is needed. Smoooooth.

My previous one for years was 10”x12”x 1-1/2”. It did the job but the large surface definitely makes it easier and the price was right.

 

[Rod MacDonald]

My own post bring me back to another point.
Long base bevels.
Is a one degree base bevel the same on a base edge with 1.5mm's vs a 2.5mm thick base edge? Assume with both thicknesses you did NOT do it long.
Only bevel the steel edge. Do not extend into the base plastic!
So one degree at a distance of 1.5 vs 2,5mm length of edge.
Which ski is going to ski better?
All you 0.5 base bevel folks, please chime in!

You won't be able to tell any difference. The height difference between the flat base and the outer edge is 0.017mm
The thickness of a sheet of A4 paper is 0.1mm (5x larger).

 

[Jacques]

You won't be able to tell any difference. The height difference between the flat base and the outer edge is 0.017mm
The thickness of a sheet of A4 paper is 0.1mm (5x larger).

So a long base bevel to extend into the base about 2mm or so would be the same as not?
Most folks say never bevel the base edge to extend into the base material.
Say my base edge is 2mm's wide and I bevel another 2mm's into the base. Now I have a 1 degree that would be 4mm's long.
Most would never do that, so a 1 degree at 2mm length must be better? Seems you say no difference?

 

[Doug Briggs]

You would be amazed at how many skis I get in the shop that have very high base bevels. They are worn from skidding, as far as I can tell. I don't think carving would wear them nearly as much. It is the lateral movement of the edge over snow (ice) that will wear them out.

Some are that way from tuning but that is a lot less frequent. As you base and edges wear, your skis become concave. Using a base bevel guide on a concave convex ski will create the guide's base bevel PLUS the amount of 'bevel' that results from the bases being high relative to the edges. So if your guide is 1 and your bases are 1mm high on a 65 mm waist ski, you are cutting about a 3 degree bevel in the edges as the guide is at about 2 degrees (using the 60mm rule) and cutting another 1 degree.

I had one customer bring in his SL skis and ask for an edge and wax. He said he couldn't get them sharp. He had worn or 'tuned' a 4 degree base bevel into his skis. He thought he was setting a 3 degree side bevel, but he was at about 2, but that is a guess since his bases were high. I think his issue was mostly tuning technique. He has had this issue before. The solution was to blank his skis and set the bevels anew.

Coaches skis are notorious for having high base bevels from wear as they are almost always side slipping.

 

[Doug Briggs]

We use a true bar and eye to determine base flatness and consistency of base edge. We also use it and eye alone to roughly determine the base bevel. When evaluating for a customer we use the SVST type of gauge that utilizes a magnet to align the tool in a way similar to @Noodler 's method with the clamp. The magnet aligns to the base or side edge bevel and you then read the bevel on one of two scales; one for base, one for side.

Knowing the base bevel with extreme accuracy going into a tune isn't essential, just knowing that the bevel is significantly out of the desired range is all that is needed. I tune by eye with both hand tools and the Scout. If I can see that the entire edge is being cut, I know I've achieved the angle I want and I stop setting that edge's bevel. I, as we all do, rely on the hand tools and machine to provide the desired bevels. You have to trust your tools are accurate. You can verify the accuracy of a fixed guide, but you can't change it. The disc edger is calibrated using a Wixie and has infinite adjustment. It is as accurate as the Wixie: .1 degree.

 

[dbostedo]

^^^^
Minor correction @Doug Briggs ... center of the base higher than the edges (center of the ski thicker than the edges) would be convex, not concave.

 

[Jacques]

^^^^
Minor correction @Doug Briggs ... center of the base higher than the edges (center of the ski thicker than the edges) would be convex, not concave.

I thought something strange there too. He seemed to be talking about both edges. His post confused me.

 

[Rod MacDonald]

So a long base bevel to extend into the base about 2mm or so would be the same as not?
Most folks say never bevel the base edge to extend into the base material.
Say my base edge is 2mm's wide and I bevel another 2mm's into the base. Now I have a 1 degree that would be 4mm's long.
Most would never do that, so a 1 degree at 2mm length must be better? Seems you say no difference?

That wasn't the question you asked. I merely pointed out the infinitesimal difference between 1deg angles over 1.5 v 2.5mm length.

 

[Doug Briggs]

^^^^
Minor correction @Doug Briggs ... center of the base higher than the edges (center of the ski thicker than the edges) would be convex, not concave.

Thanks. I corrected it in place. Thanks to the new strikeout option, it is easy to leave the bad and replace with the good.

 

[Jacques]

That wasn't the question you asked. I merely pointed out the infinitesimal difference between 1deg angles over 1.5 v 2.5mm length.

You are right. I'm just trying to go deeper. I loved your first response. I need more trigonometry people to help out here.

 

[Jacques]

Thanks. I corrected it in place. Thanks to the new strikeout option, it is easy to leave the bad and replace with the good.

Ha ha. You are good Doug! "Objects in mirror can be closer than they appear!" Convex! The terms always vex me!

 

[ScottB]

Jacques,

I can do the math or trig if you want. But just some thoughts for now. If you cut your bevel into your Ptex base, the angle stays the same but the distance the outer tip of the edge rides off the snow is greater. Think of the snow surface as a perfectly flat granite block to keep things simple (it is obviously not, so real world results are always less dramatic). What happens is the pivot point of the ski is different by how much you went into your Ptex. I do think you will feel this, although in theory you rotate the ski the same angle to get the tip to touch the snow, but it moves a greater distance. Once you apply force to the edge, I think it will feel different.

Ideally, the Ptex should be flat all the way across the width of the ski and meet the metal edge flush. Just the metal edge should be angled or beveled. I think this will give consistent results as the ski is ground flat again from time to time and the edges reset.

 

[ScottB]

Back to the OP's 8 deg base bevel.

That maybe on one spot on the ski and not along the entire length. Typically base bevels vary along the length on worn skis. Mike always gets the bevels very consistent along the length when he completes a tune.

I had him tune about 10 skis one year due to another tuner screwing them up. I couldn't believe how well every single ski skied after he tuned them. Way better than they have ever skied. More grip, no twitchyness, perfectly smooth across snow transitions. The skis just did what they were supposed to and I didn't have to put any effort into keeping them in line. Very relaxing skiing on them.

 

[Jacques]

Jacques,

I can do the math or trig if you want. But just some thoughts for now. If you cut your bevel into your Ptex base, the angle stays the same but the distance the outer tip of the edge rides off the snow is greater. Think of the snow surface as a perfectly flat granite block to keep things simple (it is obviously not, so real world results are always less dramatic). What happens is the pivot point of the ski is different by how much you went into your Ptex. I do think you will feel this, although in theory you rotate the ski the same angle to get the tip to touch the snow, but it moves a greater distance. Once you apply force to the edge, I think it will feel different.

Ideally, the Ptex should be flat all the way across the width of the ski and meet the metal edge flush. Just the metal edge should be angled or beveled. I think this will give consistent results as the ski is ground flat again from time to time and the edges reset.

Ideal for one person my not be ideal for another. Nevertheless, I like what you are saying.

 

[Sibhusky]

Well, I didn't think Jacques LEFT the ptex base like that. I thought it was a start to get the metal the right angle, then he flattened the base afterwards. Jacques?

 

[Jacques]

Well, I didn't think Jacques LEFT the ptex base like that. I thought it was a start to get the metal the right angle, then he flattened the base afterwards. Jacques?

Sometimes yes & sometimes no. More often than not, I will steel scrape a worn convex base back to a flatter condition, then I will work on the base edges. Given that, I will almost always bevel into the plastic just a touch. It can be needed to get a more consistent base bevel. Then, I may or may not steel scrape the base some more.
I like a slightly longer base bevel. Seems most folks can't tell. They can tell the base is flatter though.
I also don't mind a base that has a bit of convexness in the tips and tails. It provides that variable thing people talk about. The ski will be easier for many to ski like that. Not so fast to hook.
I have learned all this from years of purchasing old and well-used skis, then making them work pretty good again.