Thread: Why do scales warp?

Originally Posted by Rawaz

Interesting discussion! If I just may ad a question related to this: why do blades get warped? I have an old slightly warped wedge razor. And can something be done about it or warped scales for that matter?

Unlike scales that become warped blades are that way from the beginning. Just a manufacturing defect. Unless someone puts a razor to alot of heat I don't see the blade warping over time. You can hone it with a very narrow hone or use a rocking motion as you hone.

The plastic scale shrink because some of the chemicals used in the manufacture of the plastic is slowly released as gas, when the gas is released, the total volume is reduced by a small amount (it shrinks). However, the metal inlay will not shrink, and is firmly attached to the scale… so something has to give, the result is bending of the plastic (the dreaded warp) or the thin metal inlay will buckle and some parts lift of the scale.

It’s a similar principle, the bimetallic strip.

All plastics slowly shrink over time, even modern plastics, some much slower than others.

I guess nothing lasts forever.

I hope this "long wind" helps some.

interesting discussion ...

From what I know about polymers ...

Polymers tend to warp all by themselves. It's due to the actual molecular chain. Imagine a piece of spaghetti ... thats what the molecular chain - in technical terms ... the polymer - resembles. Anyways, when this chain is broken, it will tend to bond to another chain to regain molecular stability. This re-bonding causes warpage.

So, the next question is ... How does one go about ensuring the polymer doesn't warp after casting?

- Dont cut it.
- Don't poke holes in it.
- Cast all of the detail in the mold.
- Sell it as fast as possible (ha ha)

Basically try not to damage the polymer chain(s), forcing them to rebond.

Once I worked for a company that sold parts cast from nylon. These parts would have a shelf life of about 6 months because the cast details would warp from just gravity and sitting on the shelf. Of course, this is an extreme example when discussing razor scales but I would think that all polymers react in this fashion in some way, shape or form. The time frame would probably depend on which additives were addded to the polymer to slow this warpage process.

There are literally thousands of combinations when discussing available polymer additives. It's tough to lay out a blanket statement about warpage that would cover all of the available combinations.

Just for conversation's sake ...
The same company I worked for regarding nylon found out that plain old water, of all things, acts as a surface hardening agent to nylon66; directly analogous to the carbon and steel relationship.

So ...
Which polymer combination does Dovo use? I have absolutely no clue. From what you describe, it sounds as if the scales experience some post cast drilling.

Hope this helps

Originally Posted by RayG

The warping is very mild and is on the body of the scale just where the "Dovo" inlay is. Funny thing is, it only involves the scale with the inlay. The other side is perfectly straight. May be something related to the metal inlay?

I also had a razor whose scales were bowed only on the side with a pearl inlay. It seems to match what Smythe is talking about

I'm sure Smythe has got the answer - different coefficients of thermal expansion. Only the scale with the inlay is affected, which would seem to confirm it. If both scales had warped, the propensity of the metal to expand/contract at a different rate to the plastic would not be the reason for the warp.

Regards,
Neil.

I’ve been told that I’m warped, you’d think I could help on this one.

Just to add to this old chestnut of a thread, since it has popped up again... Most of the metal inlays were applied with a heat stamp. And has been said, heat can make things happen!