Thread: Hinge pin mechanics

Originally Posted by bluesman7

Gugi described the elegant action of the hinge/scale interaction very well in another thread as such.

Gugi's post;


There's one more nuance to this. Without taper you have a permanent stress on the scales/pivot in any position, which means that over time they deform a little and relieve the stress a little making the scales looser than what you want. So you have to retighten them.

With the taper at the wedge and the tang and flexible bowing out scales the extra stress (which causes the increased friction and scales staying tight) only during shaving. Provided you keep your razors closed when no shaving there is no deformation/loosening.

I have a few razors with a wedge and never close them too far nor open too far and close them when not in use but they have become loose and needed a little tapping on the anvil to retighten. So this theory would be debunked. That is if I understood this correctly.

Some of you guys are not reading between the lines here at all..

If a "Well Designed" razor is failing within 5 years some within 2 then perhaps just perhaps that design wasn't such a great idea..

and with that I am outta this convo...


ps: 3rd pin

There are many theories as to why they are there, none are proved

Originally Posted by Michael70

I have a few razors with a wedge and never close them too far nor open too far and close them when not in use but they have become loose and needed a little tapping on the anvil to retighten. So this theory would be debunked. That is if I understood this correctly.

You can never avoid friction, it will deteriorate any mechanism eventually.
What you are missing is that when you use a spacer instead of a wedge, on a tapered tang blade , then the scales will get deformed and the razor will stop functioning properly very fast. As I said before I have a razor that was made like that and at less than a year of age the scales are already deforming because the are buckling in and are hitting the tang. The tang now is pushing the scales out and that will soon lead to loose pins. On a properly executed razor eventually, after years of use, the pins will loosen up, but the scales will not deform provided the pins are not bent or the pin holes are not skewed. All that it will take to "fix"the issue is tap the pins a few times. On the razor I described above ,new scales will have to be made soon. Correspondingly, one should not use a wedge for the scales of a razor that is made with a straight tang, that will lead to issues as well.

Originally Posted by Michael70

I have a few razors with a wedge and never close them too far nor open too far and close them when not in use but they have become loose and needed a little tapping on the anvil to retighten. So this theory would be debunked. That is if I understood this correctly.

No, that's not how you debunk a theory. You have to compare the alternative design and show that it performs better. Because the claim is not that the scales will never get lose with correct taper, just that without it it will happen much sooner.

You make two blades, one with straight shank and one with tapered, scale the first one with straight scales, the second with properly flexing scales and make sure you have the same tension on both pivors (I can suggest number of ways to ensure that). Then you open and close them the same way the same number of times and find out which gets looser first.

That's how you debunk the theory, if it is wrong, and find supporting evidence if it isn't

Originally Posted by mainaman

What is your point here?

My point is that, just because something is done a certain way, and it is successful, does not eliminate the possibility of doing that same thing in a different and equally successful way.

By the way, how many angels are dancing on the head of this pin?

Originally Posted by pixelfixed

Orville,your obviously a great fan of spacers because that is what you have,so be it, enjoy.
But to many others,they are just down right ugly

And that is fine. I am neither a fan nor a detractor of wedges OR spacers. I am a fan of good shaves. I have some razors with spacers, and some with wedges. My two best come 1 from each. I simply reject the notion that if wedges are good, spacers must inherently be bad.


And with that, I am done.

Wow,
This has been an intense read for me! My brain is now hurting. Lol a lot to think about. And I'm very glad that I stumbled upon this one and read it all. I have some important adjustments to make in my designs.

I have a question: when making scales for a blade and considering an exotic material that does not, will not bend well... Let's say mammoth bark.. would one want to put it on a blade that has a flat tang with no taper? Or perhaps carve the mammoth scales to have an inherent curve?
Thanks in advance for the info and also everybody else who have made this my favorite informal SR read yet!

Originally Posted by MikeT

I have a question: when making scales for a blade and considering an exotic material that does not, will not bend well... Let's say mammoth bark.. would one want to put it on a blade that has a flat tang with no taper? Or perhaps carve the mammoth scales to have an inherent curve?

I think you want to consider first what are the stresses that are going to be generated in one design or another, what would their effect be and what is the most important thing you need to address.

Mammoth, like elephant ivory, may not be very flexible when thick but it still deforms plasticly and elastically and can take certain stress with small damage. But it is very dimensionally unstable with respect to humidity, so one thing you must avoid at any cost is gluing it to material which is not affected by humidity e.g. metal. The reason so many vintage razors with ivory scales are cracked at the wedge is because somebody was ignorant enough to glue the wedge to the scales.

Or if you take glass it is a lot more challenging because it fractures easily under these stresses. But some years ago somebody put glass scales on a wapi and it was fine. To make sure the scales are not subjected to stresses that will break them they used a lot of polymer washers: http://straightrazorpalace.com/custo...yes-glass.html

Most problems are from people not understanding or not even thinking and just making something assuming that it will work fine. But if you consider your specific case with its specific requirements that must deviate from the norm it's not too hard to decide what is the best way to address the potential problems.

Very informative and clear thank you. I hadn't thought about how various materials will deal with environmental changes.. So considerations like not glueing materials that react different together.. and paring materials that DO react similar..
I imagine material testing science projects in my basement.. closed in for days on end with all manner of smells and sounds finding their way through the cracks of the floor scaring my poor family! Lol. Muah hah hah hah!!!

Mammoth Ivory is no where near like working with elephant Ivory,JMO

Originally Posted by Orville

By the way, how many angels are dancing on the head of this pin?

Actually, they dance on the point not the head & the figure is estimated to be approx. 1000 according to Dr. Philip Schewe, but nice pun



Speaking of pins, whilst this has been a discussion mostly on wedges vs spacers etc.. there was only little mention about microfasteners.

One thing no one mentioned is that using them will often add bulk to the scales. So what you say ?

Well, if that razor is vintage & came with a paper coffin, it most likely will not go back into it again due to the extra width.
Not so much functionality of the razor but a restorer should consider this.