EpicSki › The Barking Bear Forums › On the Snow (Skiing Forums) › Tuning, Maintenance and Repairs › Why is base edge beveling filing the plastic base?
New Posts  All Forums:Forum Nav:

Why is base edge beveling filing the plastic base?

post #1 of 17
Thread Starter 

Ok, this has got me stumped confused.gif

 

I took a couple of short strokes with my new SVST final cut base bevel guide and noticed the file was contacting the plastic base eek.gif so I stopped before I did any more damage.  Here's what it looked like.  You can see the dull area on the top where the file was rubbing the plastic.

 

DSCF5394.JPG

 

So I started to think....what could cause that?  Well, it could be that the base isn't flat, so the guide bar resting on the ski base is deeper into the ski than it should be.  So I checked again with my true bar in that spot (pic below).  Although there is some slight concavity in the center, the parts of the base near the edges (where the guide runs) seem flat enough.  So that's not it.

 

(Note that on the left of the pic below, near the edge, you can see a tiny bit of light creeping through.  This is where the file took off some of the base after two light passes with almost no pressure!  What a sensitive test!)

 

DSCF5399.JPG

 

Ok, so it's not the base flatness that's at fault.  What else could it be.  Well, maybe the edge already has a greater bevel than the 1 degree my guide is set for?  That might cause it.  Although I already checked as best I could with a machinist's bevel protractor that this ski appears to have a 1 degree base bevel, perhaps I goofed, so I checked again with the true bar.

 

I laid the true bar on the edge so that no light got through between it and the edge, and then measured the gap between the true bar and the base 60 mm away.  The gap was right on 1mm, so the base angle is arctan (1/60) = 0.95 degrees, or 1 degree close enough.

 

DSCF5398.JPG

 

So the existing base bevel isn't the problem.

 

The only other thing I can think of is that the file isn't flat, or the plastic extends up a bit above the inside edge of the metal base edge ....the opposite of being "railed", not sure if there is a word is for that....derailed? tongue.gif.  But I couldn't see any evidence of that just by eyeballing it.

 

Anyway, I stopped messing with the ski before I did any more damage.  I'm planning on getting this pair stoneground at the end of the season, so hopefully all will be well after that?

post #2 of 17

Are you going from a 1 base to a 0.5 base?

post #3 of 17
Thread Starter 
Quote:
Originally Posted by Ghost View Post

Are you going from a 1 base to a 0.5 base?

 

Sorry, I forgot to mention that my guide is 1 degree, the same as the existing base bevel (so far as I can tell).
 

 

post #4 of 17

If the existing base bevel on the edge has the metal beveled all the way to the edge where it meets the p-tex, you can't take any metal off of it at that same angle without taking some base off too.  That's one reason to wait until you get a base grind (which takes material off the base) to sharpen the base, so that your outside edge stays down close to the base.  Personally I just sharpen the edges and get the base bevel done with the grind. 

 

Maybe some-one can find that diagram that's floating around this forum. 

post #5 of 17

My friend who is a WC ski tuner says that once they set the base and side edge bevel on a WC ski they almost never touch the base edge. So Renenkel, what is your reason for fooling with the base bevel?

post #6 of 17
Thread Starter 
Quote:
Originally Posted by DanoT View PostMy friend who is a WC ski tuner says that once they set the base and side edge bevel on a WC ski they almost never touch the base edge. So Renenkel, what is your reason for fooling with the base bevel?

Just wanted to get rid of some nicks.

 

post #7 of 17
Thread Starter 
Quote:
Originally Posted by Ghost View Post

If the existing base bevel on the edge has the metal beveled all the way to the edge where it meets the p-tex, you can't take any metal off of it at that same angle without taking some base off too.  That's one reason to wait until you get a base grind (which takes material off the base) to sharpen the base, so that your outside edge stays down close to the base.  Personally I just sharpen the edges and get the base bevel done with the grind.


Of course, that makes sense!  Yeah, it looks like the edge is already beveled all the way to the plastic, so of course you can't take of more without taking some plastic too.  Duh!  I guess I was having a blond moment redface.gif  Thanks for the enlightenment.  I think I'm awake now (well, almost) smile.gif

 

Does that mean when you first set the base edge bevel after having the bases ground flat, you shouldn't bevel the edge all the way to where it meets the p-tex, to allow for future touch-ups (removing nicks, corrosion, etc.)?

 


Edited by renenkel - 2/13/12 at 1:02pm
post #8 of 17

You don't bevel the base with a diamond file. Unless you have some very deep striations in the base edge from the base  structure being carried over on to metal edge form stonegrinding, there is really no need to do mcuh base edge polishing.

 

Once the base edge is set and minimally polished, you never need to touch the base edge again.

 

trying to remove insignificant knicks andin the base edge is an effort in futility. In other word you gain nothing and probably make things worse.

 

ALL maintainace is done on side edge only once your base edge is intially set after a flat grind.

 

If the dings get that bind, reset your set edge with a file and a series of stones again.

 

By the way when beveling the base edge you should be using the finest race file you can get. Something in the 18-20 TPC range. Particulalry sinse base edge beveling is so important and you do not want to overbevel. Some suggest an 8" Mill bastard file. I vehemently disagree.

 

I use a 6" Holmenkol Crystal Race file Very short teeth and 18 TPC

 

http://www.artechski.com/Holmenkol-Crystal-Finish-Racing-File-6-inch-18-Tpcm-7433.aspx

post #9 of 17
Thread Starter 
Quote:
Originally Posted by Atomicman View PostYou don't bevel the base with a diamond file. Unless you have some very deep striations in the base edge from the base  structure being carried over on to metal edge form stonegrinding, there is really no need to do much base edge polishing. [more good advice deleted]


Thanks for all the thoughtful advice.  And thanks for being kind enough not to call me the complete fool that I undoubtedly have shown myself to be! eek.gif

 

post #10 of 17

 

Learning this stuff is a process of trial and error. Trust me when I say I had some pretty bad tunes i did early on.

 

You might want to reread my post, I fixed some grammar, spelling and clarified a bit.

 

 

also, that diamond stone is probably not beveling the p-tex just putting supeficial scratches in the in it. The pressure on your diamond file or any file or stone should be concentrated with thumb pressure directly over the metal edge.

Quote:
Originally Posted by renenkel View Post


Thanks for all the thoughtful advice.  And thanks for being kind enough not to call me the complete fool that I undoubtedly have shown myself to be! eek.gif

 



 


Edited by Atomicman - 2/13/12 at 5:44pm
post #11 of 17

The SVST Final Cut tool should - if everything is the way it's supposed to be - not be capable of "overbeveling" the edge.

 

Simpler guides (like wrapping tape around a file) can overbevel, because they lift the inboard side of the cutting tool a set amount, and leave the outboard side free. That SVST tool - in addition to having a lift away from the edge - has a set of black plastic feet that sit on the base near the edge, and a metal shelf that extends beyond the edge and supports the cutting tool. Unlike cheaper tools, it's supposed to be made with sufficient precision so that the file (or other tool) won't cut the edge (or the base) beyond the desired bevel. The tool simply stops cutting once the limit is reached. If you used a half-degree guide on an edge that's already beveled one degree, it wouldn't do anything: the cutting tool wouldn't even touch the edge.

 

From the first photo, it's not super clear what's happening to your base there. It's possible (?) that the "stripe" into the PTex is actually the result of the plastic feet of the guide rubbing against the base. That could happen if you press down hard on the guide. Don't do that. Generally, you don't want to bear down very heavily on anything. "Let the  tool do the work," as they say.

 

It's also possible that you're bowing the diamond stone slightly, That's possible with quite a bit too much pressure. But - if you were doing that - I'd more expect to see it affecting the base halfway between the edge and inboard support, rather than that close to the edge. I suppose the slight concavity in the middle might make it miss there while still contacting the base closer to the edge, but that still seems less likely.

post #12 of 17


Moonflex diamonds backing are pretty damn stiff. I don't think you could bend it that much. The feet are made of delrin and are very smooth on the bottom.

 

And sj with all due respect, I know SVST says you can't overbevel with the tool and it seems like you should not be able to,  but I guarantee, you can!

Quote:
Originally Posted by sjjohnston View Post

The SVST Final Cut tool should - if everything is the way it's supposed to be - not be capable of "overbeveling" the edge.

 

Simpler guides (like wrapping tape around a file) can overbevel, because they lift the inboard side of the cutting tool a set amount, and leave the outboard side free. That SVST tool - in addition to having a lift away from the edge - has a set of black plastic feet that sit on the base near the edge, and a metal shelf that extends beyond the edge and supports the cutting tool. Unlike cheaper tools, it's supposed to be made with sufficient precision so that the file (or other tool) won't cut the edge (or the base) beyond the desired bevel. The tool simply stops cutting once the limit is reached. If you used a half-degree guide on an edge that's already beveled one degree, it wouldn't do anything: the cutting tool wouldn't even touch the edge.

 

From the first photo, it's not super clear what's happening to your base there. It's possible (?) that the "stripe" into the PTex is actually the result of the plastic feet of the guide rubbing against the base. That could happen if you press down hard on the guide. Don't do that. Generally, you don't want to bear down very heavily on anything. "Let the  tool do the work," as they say.

 

It's also possible that you're bowing the diamond stone slightly, That's possible with quite a bit too much pressure. But - if you were doing that - I'd more expect to see it affecting the base halfway between the edge and inboard support, rather than that close to the edge. I suppose the slight concavity in the middle might make it miss there while still contacting the base closer to the edge, but that still seems less likely.



 


Edited by Atomicman - 2/14/12 at 12:02pm
post #13 of 17

Possibly he's letting the guide lift off the ski, or the stone lift off the guide, a little bit on the inboard side (the metal crosspiece)?

 

The photo of the base is a bit hard to interpret. If he's simply overbeveling, he's overbeveling a lot: the portion of the base that seems to have been affected (somehow) extends in quite far. That makes me think it's something else.

 

It's hard to see how the stone could really hit the ski base there, unless something's out of whack. It's pretty much exactly where the feet are.


Edited by sjjohnston - 2/14/12 at 1:50pm
post #14 of 17
Quote:
Originally Posted by renenkel View Post


Of course, that makes sense!  Yeah, it looks like the edge is already beveled all the way to the plastic, so of course you can't take of more without taking some plastic too.  Duh!  I guess I was having a blond moment redface.gif  Thanks for the enlightenment.  I think I'm awake now (well, almost) smile.gif

 

Does that mean when you first set the base edge bevel after having the bases ground flat, you shouldn't bevel the edge all the way to where it meets the p-tex, to allow for future touch-ups (removing nicks, corrosion, etc.)?

 


What determines how quickly the edge engages when the ski is tipped is not actually the angle but the distance between the edge and the snow.  An edge beveled at 1 degree for the full width of the metal will leave the edge a certain distance above the snow.  If you bevel half the width of the metal at 1 degree the edge will behave like 1/2 degree.  (of course all of this only matters on very hard snow--if the snow has any give the edge will already be engaged with the ski flat.) The Tognar web site gives the same advice as DanoT--after the base is ground and the base and side edges are set just polish the side edges as necessary.  (of course WC racers don't have to deal with rocks, do they--I use a file on the side edges to get rid of burrs--but as little as possible--you only have so much edge.) 

 

post #15 of 17
 
 
 

     Quote:

Originally Posted by Atomicman View Post

And sj with all due respect, I know SVST says you can't overbevel with the tool and it seems like you should not be able to,  but I guarantee, you can!


Yep, that's why ski tuners "in the know" use the Toko base bevel guide which extends across the entire ski width.  I have both tools (Toko and SVST) and I will only use the Toko when setting my base bevels.

 

A very wise man provided this very same advice here on Epic many moons ago.  I wonder who that was?  wink.gif

 

post #16 of 17

But:

 

The advantage of having the tool astride the entire base is so that the inboard side doesn't go down if there's some concavity to the ski (as is sometimes the case near the tip, or tail, notably on some Atomics, but possibly on other skis as well). The result of going down into the concavity would be underbeveling, not overbeveling. If the concavity is only at the ends of the ski, it would bevel correctly underfoot and underbevel at the ski ends, which is backwards from how you'd do things if you were intentionally varying the bevel between the middle and ends of the ski.

 

It could also - as the OP noted - also result in catching some base under the cutting tool, while missing the edge altogether. In any event, his original post seems to have eliminated that possibility (perhaps too quickly?).

 

If the base is convex, of course, you've got a whole different problem, and it's one that (a) you should fix with a proper grind in any event and (b) isn't improved by using a longer guide.

post #17 of 17



icon14.gificon14.gif

Quote:
Originally Posted by sjjohnston View Post

But:

 

The advantage of having the tool astride the entire base is so that the inboard side doesn't go down if there's some concavity to the ski (as is sometimes the case near the tip, or tail, notably on some Atomics, but possibly on other skis as well). The result of going down into the concavity would be underbeveling, not overbeveling. If the concavity is only at the ends of the ski, it would bevel correctly underfoot and underbevel at the ski ends, which is backwards from how you'd do things if you were intentionally varying the bevel between the middle and ends of the ski.

 

It could also - as the OP noted - also result in catching some base under the cutting tool, while missing the edge altogether. In any event, his original post seems to have eliminated that possibility (perhaps too quickly?).

 

If the base is convex, of course, you've got a whole different problem, and it's one that (a) you should fix with a proper grind in any event and (b) isn't improved by using a longer guide.



 

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Tuning, Maintenance and Repairs
EpicSki › The Barking Bear Forums › On the Snow (Skiing Forums) › Tuning, Maintenance and Repairs › Why is base edge beveling filing the plastic base?