Just what is Jack Knife?

[rea1eye]

Just what makes a knife a Jack Knife? I know the 2 blade Case Jack Knife has

both blades coming out of the same end. I have a Case 6118 which has

one blade and is called a Serpentine Jack.

Bob

[Old Hunter]

I think in an overarching way a "jackknife" is any pocketknife. Among knife manufacturers it varies. Among collectors we get to splitting frog-hairs and have many nuances of the definition. To me a jackknife is a two blade pocketknife with both blades pinned on the same end that doesn't have another assigned name (i.e., Barlow, Trapper, etc.) OH

[jerryd6818]

I'm with you Colonel. Others can call it what they may but your definition is what I use.

[KnifeSlinger#81]

I agree with Bruce. In addition a moose pattern is sometimes called a texas jack in catalogs.

[steve99f]

I think the term jack knife describes a type of pocket knife. It's type is as described by OH. A Barlow, trapper or copperhead are all jack knives are they not?

[Dinadan]

I agree with Jerry - when I think Jack knife I think two blades pinned on the same end. But it does seem to be quite difficult to give a precise answer because of all the different usages. Think Farmer's Jack and the blades are on opposite ends: I always thought that knife should have a different name.

[FRJ]

I think in an overarching way a "jackknife" is any pocketknife.

I think this statement is pretty descriptive.
Most people with minimal exposure to pocket knives would probably use this term.

Pocket knife collectors us a a more refined terminology.

[kootenay joe]

Folding knives as a group can be divided into Pen knives & Jack knives each of which has a great many different patterns. In general a Pen knife is under 3 1/2" and of lighter construction. A Jack knife is usually 3 1/2" or larger and of a more heavy duty construction. There are many knives that could be in either group in which case the decision is usually made by the robustness and intended use for the knife. The number of blades is not the deciding factor.
kj

[tongueriver]

I think in an overarching way a "jackknife" is any pocketknife. Among knife manufacturers it varies. Among collectors we get to splitting frog-hairs and have many nuances of the definition. To me a jackknife is a two blade pocketknife with both blades pinned on the same end that doesn't have another assigned name (i.e., Barlow, Trapper, etc.) OH

I have always liked this definition the best.

[Edgewise]

Just what makes a knife a Jack Knife? I know the 2 blade Case Jack Knife has

both blades coming out of the same end. I have a Case 6118 which has

one blade and is called a Serpentine Jack.

Bob

I think your profile picture is a good example of a jack knife, together with what this thread says.

[Mumbleypeg]

I think in an overarching way a "jackknife" is any pocketknife. Among knife manufacturers it varies. Among collectors we get to splitting frog-hairs and have many nuances of the definition. To me a jackknife is a two blade pocketknife with both blades pinned on the same end that doesn't have another assigned name (i.e., Barlow, Trapper, etc.) OH

I have always liked this definition the best.

I was thinking I agree with this too, until I thought of the "English jack" which in my mind is a single blade knife.

Ken

[jerryd6818]

I think in an overarching way a "jackknife" is any pocketknife. Among knife manufacturers it varies. Among collectors we get to splitting frog-hairs and have many nuances of the definition. To me a jackknife is a two blade pocketknife with both blades pinned on the same end that doesn't have another assigned name (i.e., Barlow, Trapper, etc.) OH

I have always liked this definition the best.

I was thinking I agree with this too, until I thought of the "English jack" which in my mind is a single blade knife.

Ken

I have a small collection (10) of English Jacks and they all have two blades. All the ones I would like to add to the collection and the vast majority of the English Jacks I have ever seen, all have two blades swung from the same end. The only variation I've seen with English Jacks is someone calling a knife that's shorter than 4½" closed an English Jack. I rarely see a single blade.

[Mumbleypeg]

I hear ya Jerry. But here's what Levine's Guide says "English jacks most often have a single clip blade. Others have a spear blade instead. Some have a pen second blade."

When I envision an English jack, in my mind it's a large (over 4 inches) knife with a clip blade, often a lockback. Like a Case Cheetah or large coke bottle pattern. But your two-blade examples fit the Levine definition too.

Ken

[TwoFlowersLuggage]

I have always thought that in most old juvenile novels, they used "Jack Knife" to mean any manual folding pocket knife. When a truck & trailer "jack-knife", it folds.

[kootenay joe]

"they used "Jack Knife" to mean any manual folding pocket knife"
I agree, but here in a knife forum we should use the term "Jack knife" more specifically so that Pen knives & Multiblades are excluded.
Knife terminology varies with geography. In LG4 BRL has attempted to bring some standardization by defining knife words based on their original use. He divides knives into 3 groups: Jack, Pen & Multiblade.
A Jack is a STOUT knife with blade or blades usually all hinged on the same end but some have blades hinged at both ends. It is not the number of blades or their placement in the frame, but "Stoutness" that is the basic feature that all Jack knives must have.
kj

[deo-pa]

For what it's worth:

Merriam-Webster Dictionary : A large strong pocketknife
Webster's Dictionary (1913 edition): A large, strong clasp knife for the pocket; a pocket knife
Cambridge: A large knife with a blade that folds into the handle
Dictionary.com: A large pocketknife
Google: A knife with a folding blade
Oxford Living Dictionary: A large knife with a folding blade
Oxford Advanced American Dictionary: A large knife with a folding blade
Vocabulary.com: A large knife with one or more folding blades
MacMillan: A small knife with a blade that folds into its handle
Collins: A large pocketknife
Longman Dictionary of Contemporary English: A knife with a blade that folds into its handle
Chambers Dictionary: A large pocket knife with a folding blade
American Heritage: A large clasp knife
Wikipedia: A compact foldable knife
Reverso Dictionary: A knife with a blade pivoted to fold into a recess in the handle

Anybody have a copy of the OED? It's not available online.

Ya I know I've got way too much time on my hands. But there is a foot of snow and we're not plowed yet and this beats my other task for today: paying bills.

Dennis
PS - Anybody wanna argue whether it's "jack knife" or jackknife"?

[stockman]

My favorite Jack knife. I have shown this knife before. Mostly I'm trying to learn how to post pic's on this new pc.

Harold

[espn77]

Harold, I don't blame you for that being your favorite Jack knife. Very nice

[RalphAlsip]

Harold, I thought your favorite jack knife was your Union harness jack. Can you have 2 favorites? . Just kidding. Beautiful old knife with great blades and handles. Looks like you’re a pro with the new computer.

[FRJ]

What a great knife, Harold.

I say old chap, did I hear "English Jack"?

[espn77]

I like the color on the middle knife Joe.

[FRJ]

Thanks, Keith.
That's an old American Knife, Plymouth, Conn. 4 1/2"

[TwoFlowersLuggage]

"they used "Jack Knife" to mean any manual folding pocket knife"
I agree, but here in a knife forum we should use the term "Jack knife" more specifically so that Pen knives & Multiblades are excluded.
Knife terminology varies with geography. In LG4 BRL has attempted to bring some standardization by defining knife words based on their original use. He divides knives into 3 groups: Jack, Pen & Multiblade.
A Jack is a STOUT knife with blade or blades usually all hinged on the same end but some have blades hinged at both ends. It is not the number of blades or their placement in the frame, but "Stoutness" that is the basic feature that all Jack knives must have.
kj

I absolutely agree with your concept that in a collector forum we should define terms used in describing the items with as much precision as we can. Of course, I must also note that terms like "stoutness" are very subjective. A Pen knife is certainly not stout, and on the other end of the spectrum a Camp knife certainly is stout. Between those two it gets a little more murky. A Large Stockman seems stout to me, but take the same knife and scale it down to a Small Stockman and it doesn't seem very stout. The same goes for a Regular Trapper vs a Tiny Trapper. I suspect a Peanut could probably go either way. A Canoe seems stout and a Toothpick is clearly not stout.

I guess what I'm saying is that the addition of "stoutness" helps - but we're still going to be making subjective judgments.

[espn77]

"they used "Jack Knife" to mean any manual folding pocket knife"
I agree, but here in a knife forum we should use the term "Jack knife" more specifically so that Pen knives & Multiblades are excluded.
Knife terminology varies with geography. In LG4 BRL has attempted to bring some standardization by defining knife words based on their original use. He divides knives into 3 groups: Jack, Pen & Multiblade.
A Jack is a STOUT knife with blade or blades usually all hinged on the same end but some have blades hinged at both ends. It is not the number of blades or their placement in the frame, but "Stoutness" that is the basic feature that all Jack knives must have.
kj

I absolutely agree with your concept that in a collector forum we should define terms used in describing the items with as much precision as we can. Of course, I must also note that terms like "stoutness" are very subjective. A Pen knife is certainly not stout, and on the other end of the spectrum a Camp knife certainly is stout. Between those two it gets a little more murky. A Large Stockman seems stout to me, but take the same knife and scale it down to a Small Stockman and it doesn't seem very stout. The same goes for a Regular Trapper vs a Tiny Trapper. I suspect a Peanut could probably go either way. A Canoe seems stout and a Toothpick is clearly not stout.

I guess what I'm saying is that the addition of "stoutness" helps - but we're still going to be making subjective judgments.

Interesting point of view Ken.

[rea1eye]

Thanks for all of your replies. I looked up on google "what makes a knife a jack knife"
and could not come up with something concrete. I thought maybe I was missing something
on how a knife is given the jack knife category.

It seems all my Case knives named jack knife are more of a workhorse than others
( eg Eisenhower, pen, toothpick)

Bob