Thread: Pressure Fitted pins

As someone mentioned, there is a very tiny "overlap" between the hole (scales) and the pin. For a 1/16" hole (I use SI, so 1,5785 mm) You need a tolerance class of H7/r6 or H7/s6 for a tight fit. This means there is an overlap of 4...20 microns! This is the ISO standard for pres fits. (25 microns is about 1/1000 of an inch.) The next problem is: Where can You find the special tools to make the pinhole, and the rod to the exact size.

You need special tools to even measure this measurements.

So, i'm a little sceptical with this.

(I work with such little things, so i know, that for example for measuring 10-20 micron difference You need a measuring microscope.)

I don't know, for my part, I want some friction betwen the scales and the blade I.E a tight fitted blade. I belive that would be hard to achieve in this way. Also, a pinned razor can be "thightend" by pinning it a little harder while a pressfit solution, to me, only can be looser, not tighter.

My 2 cents

I'm of the same opinion as cako72.

Although a cryo-shrink fit of a pin (or other metal parts) is a good practice in many machining situations, I do not think it will work well for razors.

Most scale materials usually have the qualities of being soft, flexible and thin. None of these makes a good, secure 'bedding' for a temperature-augmented force fit.

It is again worth stressing that when done properly the traditional method of pinning a razor with little washers on either scale only introduces inward compression forces along the axis of the razor pin, but does not place any extra outwards radial force on the scale material itself.

The traditional pinning method is simple, effective and proven to last for decades if not longer. The only thing that currently makes it seem difficult to most restorers is the lack of a proper and abundant supply of rivet material and washers.

- Ignatz

why do razor scales flex?

razor scales flex because the tang is a non-constant width. Slowly open and close and watch. I THINK this might be by design as it sort of acts like a spring to resist movement, making your scales nice and tight.

The idea btw was not to find an alternate method to pinning, but rather, a way to make flush fit pins.

As Ben.mid has pointed out, it can get a nice clean look.

I have a way of doing this, take a look at this thread:http://straightrazorpalace.com/galle...-smoke-pc.html

There I have filed the pins flush with the scale material. But, the scales need to be thick enough to allow at least 1-1.5 mm of tapering to make enough "coning" of the pin. Also, this metod stresses the material a bit, so I doubt that grained materials such as ivory and bone is a good choice. Perhaps some wood spieces can be used, just test away!

how does one taper? did you use a countersink bit?

Originally Posted by khaos

razor scales flex because the tang is a non-constant width. Slowly open and close and watch. I THINK this might be by design as it sort of acts like a spring to resist movement, making your scales nice and tight.

The idea btw was not to find an alternate method to pinning, but rather, a way to make flush fit pins.

correct and that does not place shear on the pin

all my pins have been flush without washers, they could have been flush
http://straightrazorpalace.com/galle...-one-done.html
http://straightrazorpalace.com/galle...s-shumate.html

IMHO the tightness of your pin will be entirely dependant on the ultimate bearing strength of the wood you're using (which is in the order of 1/10th that of metals and plastics). Essentially you are using a fancy way to drive a nail into the scales without splitting them.

Also, as was said, the runout on your drill is likely more than the thermal contraction you can get on a 1/16" pin in liquid nitrogen.

Cheers,
Dan (B.Eng Building Engineering)

Originally Posted by kevint

correct and that does not place shear on the pin

all my pins have been flush without washers, they could have been flush
http://straightrazorpalace.com/galle...-one-done.html
http://straightrazorpalace.com/galle...s-shumate.html

it does in fact place shear on the pin... the compressive/tensile forces due to flexing are lateral in the scale, which is normal to the pin, which is shearing. Trust me. I am at college for mechanical engineering. I know my mechanics of solids....