Tang pins...again

Originally posted by penguin_2000
Tony's comments are mostly true, but I don't think the pin would have to be perfectly square--I believe the point is to have a large surface area for contact; the 90 degree corners are not necessary.
Click to expand...
My point was twofold: 1) Maintain 360 degree contact, and with a square hole the easiest it with 90 degress corners. 2) Anything with a radius is significantly harder to mate perfectly.

Originally posted by penguin_2000
Actually, 90 degree corners would make it the handles incur almost infinite stress at the corner.
Click to expand...
It could, but the cornors will definitely sustain the most stress. But without a perfect radius match at the corners, you will develope a weak spot that will fail over time. Something avoided with a round pin.
 
OK, no mech. engineering background, no deep knowledge of bali design, but I came up with some ideas while reading this thread.

1-Make the pins like dual thumbstuds, male and female threaded pin halves attached thru the tang, interchangeable for wear

2-Eliminate the pin. Instead machine the handles with 'humps' as a contact point to a seat milled in the other half, or a replaceable bolster section on the handles with this feature. Not enough gap? Change to a handle/bolster section with a larger hump. Too much gap? Sand or file the hump down. Do the same to ensure the handles center the blade when open.

Like I said, I don't know the specifics of bali design, so if these ideas wouldn't work, please tell me why. Just tryin' to think outside the box.:)
 
Originally posted by tonyccw
My point was twofold: 1) Maintain 360 degree contact, and with a square hole the easiest it with 90 degress corners.
Click to expand...
Hmmm... I disagree with that too. If we only consider half the pin (picture half the pin with the flat part sitting on the horizon) with the handle contacting the pin at 90 degrees relative to the horizon, there really is no "contact" at either 0 or 180 degrees since the angle of incident is 0 degrees tangent to the side of the pin. And the relative force on the pin tapers off according to the sine of the angle relative to the surface of the pin. This of course takes into a pretty safe assumption that the handle does not push sideways on the pin at all.
 
Hmmm... I disagree with that too.
Click to expand...
Nooooooo, not the tang pin to the handle cup relationship. The tang pin to the tang pin hole contact relationship. Surface mating contact area of the pin to the hole. I don't care what the shape of the pin is once exposed out of the hole. The thread is about how to install the pin.
 
Originally posted by hardheart
2-Eliminate the pin. Instead machine the handles with 'humps' as a contact point to a seat milled in the other half, or a replaceable bolster section on the handles with this feature.
Click to expand...
Almost. One of the jobs of the tang pin is to prevent the handle from over rotating. Which means even Clay would have a tough time doing his manipulation if he has no idea if the handle has reach the apex of the swing. Also, without the tang pin in place, you won't be able to leverage out the blade from a closed position with manipulation.

Like I said, I don't know the specifics of bali design, so if these ideas wouldn't work, please tell me why. Just tryin' to think outside the box.:)
Click to expand...
As I've always said. Keep them coming. We all have ideas to share.
 
Originally posted by tonyccw
The thread is about how to install the pin.
Click to expand...
Sh!t, we're all talking about different things. I'm pretty sure Blasto was talking about the pin-handle contact. ...this is so frigging embarassing... :rolleyes:
 
Originally posted by penguin_2000
Sh!t, we're all talking about different things. I'm pretty sure Blasto was talking about the pin-handle contact. ...this is so frigging embarassing... :rolleyes:
Click to expand...
Welcome to ASCII cyberspace. (God I missed the old UNIX days..... )

You were right, Blasto was referring to the handle contact. But I was more focused on the insatllation, and the resulting stress transfer within the hole.
 
Originally posted by tonyccw
Welcome to ASCII cyberspace. (God I missed the old UNIX days..... )
Click to expand...
?? I still use unix. If it wasn't for the pictures on this site... I'd probably still be using lynx for my web browsing. At least I wouldn't have to have so many damn pop-up windows.
 
Originally posted by penguin_2000
?? I still use unix.
Click to expand...
Not the way I used it. Do you type and get your results on paper? That's right a terminal-printer. Dem's the good old days.....
 
I know this is an old thread.. but something crossed my mind as I re-read this for the third time.

There was a little discussion in there about two different "temperature altering" ways to get a tang pin into the handle.

1) Freeze (shrink) the pin, and slide it in.
2) Heat (Expand) the hole, and slide the pin in.

It's probably pointless to continue to discuss, since there are better alternatives and #1 was the common choice, but I've got a bone to pick with #2 above. First, I'm not an engineer, so excuse me in advance for not using the right terms.

Basically, I understand things like this: Heating metal makes it expand ("Yeah Lisa, '*Heat* makes metal expand'.. now who's talking crazy??" - Bart). ;) So you're thinking typically, you heat a chunk of metal, and it expands outwards.. so if you heat the metal around the hole, it'll make the knife expand, and the hole will increase in size.

I don't think that would work. The metal expands to fill any gaps. In a solid chunk of metal, gaps=surface area. But if you have a hole, it seems to me that the knife would tend to expand and.. shrink.. the hole. That's because the hole for the tang pin is.. somewhere more convenient for the metal to expand to than into the other metal and outwards.

In reverse, cooling the blade metal would cause it to shrink, and enlarge the hole. Why? Because the metal tends to take up less space, and would shrink away from all surface area. Hole included.

So that leaves you with two choices:

1) Freeze the pin.
2) Freeze the blade.

And since you're needing liquid nitrogen anyways now.. the pin is a lot smaller and easier to shrink... so.. Don't bother with #2.

Am I even in the right metalurgical ballpark with my reasoning? Again, I'm not asking so much for usefullness' sake, more for curiosity.
 
Originally posted by Cynake
Am I even in the right metalurgical ballpark with my reasoning? Again, I'm not asking so much for usefullness' sake, more for curiosity.
Click to expand...
You're absolutely right. But the rest of us just let this thread die because we didn't want Tony to get all worked up about it... ;)
 
Don't blame me, I didn't reference the link. And just because you said that Andrew :D .

Cynake: You're correct in that the typical reaction to heating a piece of metal with a hole is that the metal will expand and the hole will shrink. But the idea was, since the metal is now softer, inserting the pin will ensure that way will 1) allow for low resistance going in; 2) form itself around the pin, and; 3) shrinks around the pin as it cools. And since the hole was slightly undersized to begin with, that will really ensure a tight grip on that tang pin.

However, the process also requires that you then retemper the whole blade with the pin installed, the idea of having the pin sharing the same temper as the blade was the major reason I disagreed with the process. It's definitely a doable.
 
Originally posted by hardheart
OK, no mech. engineering background, no deep knowledge of bali design, but I came up with some ideas while reading this thread.

2-Eliminate the pin...

...Just tryin' to think outside the box.:)
Click to expand...

Who says BM does not listen to us? Asked for it in Nov. and they sowed it to us in Feb. Rough draft of course...:D

Now we just gotta deside what to call it.:rolleyes: ;) :D :D
 
You must log in or register to reply here.
Back
Top