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Work hardening of bases?

post #1 of 20
Thread Starter 
Starting with a well-waxed and scraped ski. Let's say it has a sintered base, so we don't get into that.

Question 1: Does or can brushing, roto, corking, or polishing actually work-harden the base after scraping?

Question 2: If yes to #1, does the wax harden or is the plastic affected?

I know nothing about bowling alley maintenance either, maybe those guys have something to say.
post #2 of 20
Work hardening occurs in the steel edge when it is deformed. When a rock is hit, part of the edge gets deformed out of shape. This action results in that bit of steel being very hard, often too hard to remove with a file. A stone is needed to remove the high spot on the steel edge.

As tuna asked, is the plastic base affected by working the wax too much?
post #3 of 20
http://books.google.com/books?id=bku...KKjJk#PPA18,M1

^ As you can see, UHMWPE appears to strain harden markedly.

Unless you are doing some stuff with scrapers and brushes that I don't do, I imagine the greatest strains are seen in the material when it is deformed by grinding and pressing processes. "Pressed" structures have gained some popularity...but I haven't researched them enough to know whether hardening of the base material is one of the reasons for that.
post #4 of 20
Thread Starter 
Quote:
Originally Posted by Garrett View Post
"Pressed" structures have gained some popularity...but I haven't researched them enough to know whether hardening of the base material is one of the reasons for that.
http://www.jenex.com/skitoolbind.pdf

page 3:

Quote:
For the rillers to work, the polyethylene base must be in
good shape, not hard and oxidized. If the base is hard, steel scrape until you encounter softer polyethylene or have your skis stone ground.
post #5 of 20
I'm not talking about rillers people are using as hand tools. I'm talking about first tier ski manufacturers selling new skis with a structure I've heard referred to as "cut" or "pressed" though I haven't seen how its done or much else about it.
post #6 of 20
Thread Starter 
Fine, fine, the riller itself wasn't the salient point, rather how those bases come to be hard on the surface that a scraper can reach softer material. It didn't look like they only meant 'hardened by first-tier factory methods'.
post #7 of 20
Yeah in any case I'm pretty sure the answer to both of your questions is no, unless you do something pretty crazy with your brushing/waxing routine.
post #8 of 20
Thread Starter 
'K. Reckon if I wanted numbers an RC car tire durometer would work? Seems they go to Shore 100A. I don't see anything cheap for D-scale.
post #9 of 20
Hmm, good question. Let us know how it goes if you try it. Cold be quite interesting.
post #10 of 20
My opinion is no. Also, UHMWPE implants and sintered bases are different physically even though they are the same chemically.
post #11 of 20
So sintered bases don't undergo strain hardening?
post #12 of 20
I am not a polymer chemist but I don't think the friction from a brush could do that.
post #13 of 20
No I completely agree with that, but I mean does UHMWPE strain harden in sintered form in general?

This talk about bases "hardening" seems to suggest it does, though to be honest I don't think I've ever noticed that feature. I don't use hand tools on skis when they get all base burnt or whatever so perhaps I've never experienced it.

Like I said originally, I would have assumed that if it does harden its when its rilled or pressed.
post #14 of 20
My guess is that if it is possible that it happens under a specific set of conditions (temperature & pressure) that may be very narrow in range and that these conditions would have to be met for some specific time frame. Basically, several things have to be "just right" for this to happen.

I remember making some things with PE and we found that in the manufacturing process if we hit a specific temp, and held that for a certain number of minutes, then end product was harder. The thought was that under these conditions the PE polymer strands lined up with each other to give a bulk material that was harder than a PE where all the strands are randomly oriented (like a pile of cooked spaghetti).
post #15 of 20
Quote:
Originally Posted by cantunamunch View Post
Starting with a well-waxed and scraped ski. Let's say it has a sintered base, so we don't get into that.

Question 1: Does or can brushing, roto, corking, or polishing actually work-harden the base after scraping?

Question 2: If yes to #1, does the wax harden or is the plastic affected?

I know nothing about bowling alley maintenance either, maybe those guys have something to say.
If the ski base becomes burnished, then it will be in fact work hardened. By doing so I speculate that you will markedly reduce the ability of your bases to absorb wax, since porosity will effectually be pressed closed. Any material that is highly porous, such as sintered metal, can be burnished, forged, or shot peened, into a more homogeneous solid material given the required pressure and or heat.

This is just speculation on my part. But if you think of the base as being a plastic lattice network, and then if you were to press into that lattice or rub it to the point that the heat generated began to deform the material such that it began to bond to itself, you can see that the resulting material would be less porous and much more rigid and solid.
post #16 of 20

The brushing, etc....

Quote:
Originally Posted by Richie-Rich View Post
If the ski base becomes burnished, then it will be in fact work hardened. By doing so I speculate that you will markedly reduce the ability of your bases to absorb wax, since porosity will effectually be pressed closed. Any material that is highly porous, such as sintered metal, can be burnished, forged, or shot peened, into a more homogeneous solid material given the required pressure and or heat.

This is just speculation on my part. But if you think of the base as being a plastic lattice network, and then if you were to press into that lattice or rub it to the point that the heat generated began to deform the material such that it began to bond to itself, you can see that the resulting material would be less porous and much more rigid and solid.
...doesn't do much negative to the base, and in the case of brushing, it probably helps maintain the structure. Bases (not edges...we've already been there) do get case-hardened, less porous, and lose structure one of two ways: (1) Base burn from skiing on super hard, aggressive snow, usually man made or injected. Hot box your skis and generally soak them with wax to help prevent this, also consider using something like Extreme Cold Powder on top of everything. (2) Lots and lots of scraping, especially with a dull scraper...so, obviously, keep your scraper sharp.

If a base does get case hardened, you pretty much need to grind it to open the base up again, then restructure it, re-hotbox it, and so forth.
post #17 of 20
Sorry, but "case hardening" has nothing to do with UHMWPE, or any PE for that matter.
post #18 of 20
Case hardening only applies to metals.

Work hardening can apply to other materials.
post #19 of 20
Thread Starter 
Quote:
Originally Posted by Doctor D View Post
I am not a polymer chemist but I don't think the friction from a brush could do that.
Question #2 might be rephrased: Can polishing pressure from a brush do it to a surface layer of wax?

No numbers to post yet, sorry.
post #20 of 20
Thread Starter 
Durometer seems to be hovering around 65-70D so far.

Fischer Revolution (left standing for years, so presumed to be "oxidized") 66D, no creep.

Head C-series brass brushed, unwaxed 67D approx. 5 second creep
same skis with Toko soft moly crayon, corked, brushed 68D approx. 10 second creep


All measurements taken at 68F on skis cooled to ambient overnight, at the vise support point to minimize flex-related artifacts.

I suspect that further numbers will be similar to the above, and I won't be able to notice anything useful until I can start accurately tracking the creep time. For example, the Heads after waxing registered 71 or 72D on initial tool contact.


To put all this in context, formica is about 94D.
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