Base Grinding

falls · Post by **falls** » Tue Apr 19, 2011 10:05 pm

Hi everyone. Just looking for some opinions on base grinding. I have made 5 pairs now. 1 was ground in Japan and they did an awesome job - looked factory quality. One was done locally and was OK. The other 3 pairs they did a horrible job to the point I am disappointed that I had to pay for it and will not get them to do any further work.
Pretty much invariably the shops have wanted to only use the stone. They say that any passes over the belt grinder will cause a convex base.
Pretty much every video of companies grinding bases out of the press involves an initial belt grind (to get epoxy off?). Then they go to the stone after that.
I was surprised recently to see that grindrite belt sanders even with an autofeed can go for as cheap as $2000 US (or better if you get a deal). Even if you ship it out here to Australia it is a lot cheaper than what I had originally thought grinding machinery was worth.
Any opinions welcome on what a shop should do for my skis.
Also on the usefulness of a grindrite type grinder.
Thanks

MontuckyMadman · Post by **MontuckyMadman** » Tue Apr 19, 2011 10:35 pm

The edges should technically be base beveled before touching the stone otherwise they will groove the stone and you will have to tune the stone more often.
The edges are harder than the base.
The ski should be flat, from the press and if not you have to use the belt to get it flat, then the stone will structure the base.
I have heard the whole "grinding the base on the belt will never make it flat". BS, the stone is for base structure not flattening, end of story.
I have several pairs of factory and my own skis I have personally flattened on a belt and then structured on a stone.
Some skis are so badly convex that no amount of grinding will get them flat and you will expose the core at the edge or grind all the edge completely away.
Them folks got it backwards I think. IMO.

powderho · Post by **powderho** » Wed Apr 20, 2011 7:12 am

One thing I've learned from this ski building venture is that factory tunes on new skis suck. I didn't realize how much better of a tune you can get. Some shops are so clueless on how to tune new skis it's borderline pathetic. I've had a pair go through the Montana robot 200+ times and not get flat. Sure the base got structure on it, but it wasn't any flatter. If you correctly belt the skis first, it will take 10-20 passes (normal new ski tune), and actually be flat. Andy up at the Peruvian shop tuned about 15 pair for me this winter and they all came out perfect. They have a narrow (1" wide) welt belt that he uses on the edges first. This will take a concave base (almost all mine are) pretty flat. The belt takes the edge down and about 1/2" of base material with it. After a few passes he will inspect the entire ski with a true-bar and focus on the areas that aren't flat. After this belt the skis really only require a few passes through the Wintersteiger machines and they are good to go. If you just feed the skis through a belt with a powerfeed, they won't get flat. Ditch the powerfeed and only sand the hi spots. I would like to get a belt in my shop too, but I don't expect to fully tune the skis. I want to get to the point I can take my skis to any shop just for the structure. My skis are dangerous with a bad tune.

Richuk · Post by **Richuk** » Wed Apr 20, 2011 9:52 am

I've wondered a lot about this in the past. I am currently around 3 -5 passes. This is to remove epoxy and not to correct the base.

I have been using quad-axial glass, only 11 gsm on the width, makes the difference? If not, then its 3 mm AL cassette, ply mould instead of mdf or the combination.

catalystsnowboards · Post by **catalystsnowboards** » Wed Apr 20, 2011 2:20 pm

Before i had a grinder i took a few boards to trigger bros in frankston, the guy who is the tech there used to work at option when they were in van and knows the grinder very well. Not sure if he is still there as it was a few years ago, but worth a try. Alot of places in australia have no clue about grinding a board!

MontuckyMadman · Post by **MontuckyMadman** » Wed Apr 20, 2011 4:41 pm

We ran a few tests and we found a hot pull was the culprit of the cupped base but less than 10 passes with an 80 grit would even clean up that cupping.
Then another 10 passes with a 100 grit and so on, but a bit to much and a lighter colored base and you sure could see the vds and even the tines on the edges.
If you are gonna make more than 5 pair a year and if you plan to sell some a base grinder was needed, in my opinion, so I found one and bought it.
Just trying to get someone else to grind your skis free or cheap was a pain and after a while they were like "are you selling these or what? They look Nice"
Here in MT we can ride year long if you hike for it. Trying to get someone to grind your skis in october when we get some early dumps is near impossible.
It was one of the last pieces in the tool puzzle so I made it happen.
The grindrites work great, there is of course a learning curve with any new tool. We have 3 in town and that's what the shops use mostly around here.
I personally love a nice autofeed.

artski · Post by **artski** » Thu Apr 21, 2011 6:28 am

This is a great subject.
I made 4 pair of skis this year (my first) and all came out with nice flat bases.
The shop near me has an older winterstieger machine but its in good shape and I know the guys there. The first pair they did for me came out edge high and I ended up flat filing them to get the edges down and after re-doing the bevel they were fine. Second pair same thing.
The third and fourth pair they took more time with more and lighter passes. They came out better but were still alittle edge high.

Have you guys had this kind of trouble? It seems to me that the belt is heating up the p-tex and maybe making it swell, and after it cools, the metal edge ends up high.
The belt is getting plenty of water.

Man I'd like to have my own belt!

artski · Post by **artski** » Thu Apr 21, 2011 6:30 am

This is a great subject.
I made 4 pair of skis this year (my first) and all came out with nice flat bases.
The shop near me has an older winterstieger machine but its in good shape and I know the guys there. The first pair they did for me came out edge high and I ended up flat filing them to get the edges down and after re-doing the bevel they were fine. Second pair same thing.
The third and fourth pair they took more time with more and lighter passes. They came out better but were still alittle edge high.

Have you guys had this kind of trouble? It seems to me that the belt is heating up the p-tex and maybe making it swell, and after it cools, the metal edge ends up high.
The belt is getting plenty of water.

Man I'd like to have my own belt!

MontuckyMadman · Post by **MontuckyMadman** » Thu Apr 21, 2011 10:00 am

I think they are edge high from your press and you just cant tell because there is epoxy on there.
They appear flat until you grind them then you see the edge highness.
Do you rout a rabbit for the edge and leave it in the press to cool?
The base does not get warm with the right coolant sometimes the edges do.
I could be wrong but this is my experience.
Powhos guys run them on a 1" belt on the edges before the grind because they know they will be slightly edge high.

skidesmond · Post by **skidesmond** » Thu Apr 21, 2011 10:42 am

falls wrote:Hi everyone. Just looking for some opinions on base grinding. I have made 5 pairs now. 1 was ground in Japan and they did an awesome job - looked factory quality. One was done locally and was OK. The other 3 pairs they did a horrible job to the point I am disappointed that I had to pay for it and will not get them to do any further work.
Pretty much invariably the shops have wanted to only use the stone. They say that any passes over the belt grinder will cause a convex base.
Pretty much every video of companies grinding bases out of the press involves an initial belt grind (to get epoxy off?). Then they go to the stone after that.
I was surprised recently to see that grindrite belt sanders even with an autofeed can go for as cheap as $2000 US (or better if you get a deal). Even if you ship it out here to Australia it is a lot cheaper than what I had originally thought grinding machinery was worth.
Any opinions welcome on what a shop should do for my skis.
Also on the usefulness of a grindrite type grinder.
Thanks

I came across this website a couple years ago and have been using some of Rays techniques (Rays Way). They work very well. If the bases are in serious shape then you may want to have a base grind done but for every day tuning this works pretty good. If your skis are fairly flat and you need to remove epoxy you can save a few bucks by using Rays Way.

http://www.alpineskituning.com/cms/

http://www.alpineskituning.com/cms/imag ... ctions.pdf

MontuckyMadman · Post by **MontuckyMadman** » Thu Apr 21, 2011 10:57 am

skidesmond wrote:
I came across this website a couple years ago and have been using some of Rays techniques (Rays Way). They work very well. If the bases are in serious shape then you may want to have a base grind done but for every day tuning this works pretty good. If your skis are fairly flat and you need to remove epoxy you can a few bucks by using Rays Way.

http://www.alpineskituning.com/cms/

http://www.alpineskituning.com/cms/imag ... ctions.pdf

I like it nice.

falls · Post by **falls** » Thu Apr 21, 2011 5:34 pm

I've seen people on vids put just one side under the auto feed. Then the other side. Same idea as montucky says with the 1" belt.
Just to clarify when you say edge high you mean concave base ie. if you sit the ski base up and lay a straight edge across it there would be a slight air gap between the base and ruler. Same same "cupped"?
This is what mine are like. I haven't got around to cutting a rebate for the teeth which I think is something I absolutely need to do.

falls · Post by **falls** » Thu Apr 21, 2011 5:43 pm

http://www.snowlist.com/Classifieds-a3271.html
this site seems to have a fair few grinders come up for sale.

artski · Post by **artski** » Fri Apr 22, 2011 8:56 am

Thanks alot for the links guys, I probably have not looked close enough at the bases, montuck you may be right about the epoxy making them appear flat. I do rabbit the edges of my cores. I rabbit in about 1mm more than the width of the edge to allow room for the fabric
How deep do you cut that rabbit? exactly the thickness of the teeth?

MontuckyMadman · Post by **MontuckyMadman** » Fri Apr 22, 2011 11:24 am

I rabbit about a half mil more than the thickness and maybe a half mil more in width wise for slop on each side. I think the fabric compresses to nothing in those areas.

Running the ski half on the autofeed and half off results in bad problems. IME. Obviously If you have an adjustable counterweight this could be doable but on my machine it has a set downforce making this a bad idea.
You could do it by hand with an edge guard, tough to make even I bet.

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