Old Jack Knife Construction

[smiling-knife]

I have these two old jack knives. The dark redbone Christopher Johnson & Co you may have seen before (new pic though) and I just acquired the stag handled Harrison Bros & Howson knife last week. What is particularly interesting about these two is the way the tangs and springs line-up flush with the end of the bolsters. See photo 3. This provides an excellent fit and smooth action with 1/2 stops. I understand that the new GEC knives are made in this fashion. Nice to see a revival of old time quality.

 

[waynorth]

When I noticed that detail on some older knives, I put some thought into it. It certainly looks nice, and presents a smooth surface to the hand and pocket. Functionally, I have my doubts about its effectiveness. In order to achieve that look, the pivot pin must be closer to the end of the bolster, because the pivot is closer to the end of the knife.
When the knife blade is open and in use, there is less bolster extending out over the tang, supporting the blade side-to-side to prevent "wobble". This is probably only relevant for extreme or repeated use, but it's worth contemplating I think.
More on the plus side, besides looking and feeling smooth, this flush detail tends to pick up less pocket lint and grit.
A mixed blessing for sure!
Thanks for bringing this interesting detail to us, s-k!

 

[smiling-knife]

Thanks very much for the analysis waynorth. Just did a quick comparison with some other jack knives that I have. Relatively speaking, the amount of tang supported by the bolster when the blade is fully open appears less (i.e. not at all), as you would imagine, from the spring-side view but about the same from the other side. I think the tangs may be shaped a little differently. These two have no wobble but that is a small sample so can't draw any conclusion. I like the looks of them lol

 

[waynorth]

I think my descriptions may be unclear s-k. The support I am talking about mostly, is the extension of the bolster pointward when the knife is open. So the (would it be "distal") ends of the bolsters, hugging the sides of the tang as the blade works. Here is a drawing that may help; please excuse the poor penmanship!

I like the looks of the knives too! And I apologize for the tangent; I guess I have hijacked your thread!!??
No wonder my wife suggests I not talk sometimes!!

 

[waynorth]

Here are two hawkbill tang ends, one as flush as possible for the varying curves, and one very deeply recessed. The flush one is much nicer looking, I think!

I should really learn to use a camera.

 

[Blues]

Great old knives and good, interesting discussion.
You think that's poor penmanship? LOL!

 

[smiling-knife]

No hijacking perceived at all. A very interesting discussion. Thanks. At the spring side there is less support. However, in the middle and from the other side it looks like a similar amount of support relatively speaking. I admit, overall, there must be less total support.

 

[waynorth]

The proof is in the results I guess. That flush hawkbill is a very tight knife. Certainly doesn't prove my theory.

 

[smiling-knife]

The comparison in the previous two pics was between the CJ and a Wostenholm both traditional jackknife patterns. This is a sample of one however and thus we can not make any definitive conclusions.

 

[Sword and Shield]

My Great Eastern has this kind of construction. Strongest half stop I've ever seen.

 

[Arathol]

"Square and clean" joints like these were at one time the sign of a well made knife. Many English-made knives were made like this, and since a good portion of early American makers had roots in Sheffield lots of older domestically produced knives were made the same way.