Handmade Teardrop Wharncliffe jacks

ashwinearl

ashwinearl

Joined
Nov 9, 2006
Messages
521
I have knifemaker membership and this knife is sold not available

This is a tear drop jack inspired by an old pattern from Japanese maker Ohta

CPM-154 wrapped in stabilized spalted hackberry
SS bolsters, caps, shield, liner, bronze washers, fluted, threaded, hollow ground
3 3/8" closed
lightish pull with the nail nick closer to the pivot.

Video of the walk/talk
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The knife looks great!!

No complaints, just legitimately curious. Why bronze washers? Just because bronze is soft I'm guessing??
 
lithicus said:
The knife looks great!!

No complaints, just legitimately curious. Why bronze washers? Just because bronze is soft I'm guessing??
Click to expand...
Thanks for the question.

I'm probably answering more than you asked here. I am not sure on why phosphor bronze as material vs another metal. I haven't seen teflon recommended much for slipjoint construction. One past post suggested that pb washers were less prone of carrying grit that could act like sandpaper over time: https://www.bladeforums.com/threads/why-phosphor-bronze-washers.344192/

Just some background on why washers at all:

A common desire for a slipjoint is to mitigate round scratches on the tang that are generated when the blade opens and closes where the liners scratch on the tang. This is mostly cosmetic but might increase some friction on the open/close.

Modern slipjoint typically use mill relieved liners. Here a mill is used to cut out a tiny pocket where the tang would come in contact with the liner. I am getting a mill or at least I keep saying I am getting a mill. I have heard of electro etch being used as well to remove the material, or dremel.

Another method to accomplish the same thing are bronze washers or other material. I am not sure why but teflon has not been recommended much for slipjoints from what I've researched. I got my from slipjoint maker Chris Taylor. Mine are 0.008" thick each. This requires thinning the blade thickness to be 0.016" thinner than the spring to accommodate the washer.

A third method used historically for a long time is to grind away small amount where the tang would scratch and with hand sending blend so it is imperceptible.

Note , bronze washer discussion here is completely different than bushing construction. Bushings are often made from similar material.

The pros and cons of Bronze washers, IMHO:
-I only have a surface grinder attachment. Getting two items (blade and spring) the same thickness is easy. getting two items to be different thicknesses by an exact amount is a PIA. This issue also pushes me to buy two thicknesses of steel, otherwise the blade comes out just 'looking' too thin.
-they are another thing to screw up or forget. For real, I have beat a slipjoint together only to see one of the washers had jumped out and is laughing at me from the bench
-for very small tanged knives, like this one, the washer has to be trimmed smaller so no part of it extends beyond the tang. I trim them with scissors another PIA
-I feel and have heard others say action feels slicker with bronze washers
-I know of several makers who have every tool in the world and by choice use bronze washers instead of milling

Until I have my own mill and several data points of milled relief vs bronze washers, I can't draw firm opinion yet. I think if I had a real stone surface grinder, the hardest part about getting blade thickness thinner than spring thickness wouldn't be an issue.


These are all just my opinion.
 
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Wow... That was all really helpful. I greatly appreciate it!!

I'll probably never be able to make my own custom knife. But as an engineer, I often think about it and I find information like this fascinating! Thanks!
 
Interesting pattern and a fine interpretation. Particularly like the scales, very effective. I assume this was made on spec for a client? I tend to prefer nail nicks on Wharncliffes rather than a long pull, they just suit the blade shape better in my opinion and I would make the end bolster slightly smaller than it is to emphasise the Rat-Tail.

Very promising work.

Hope you don't mind my observations, they are not criticisms just appreciation.

Thanks, Will
 
lithicus said:
Wow... That was all really helpful. I greatly appreciate it!!

I'll probably never be able to make my own custom knife. But as an engineer, I often think about it and I find information like this fascinating! Thanks!
Click to expand...
I am an engineer too. these things are so simple but then so complex and sensitive to the smallest issue. At the same time, my mentor says I overthink it too much. One maker says at some point they are not rocket science when I go to deep into something.
-tang shape
-order of operations
-surface grit difference between spring and tang
-hardness difference between spring and tang
-how to achieve flat
-how to hollow grind, how to flat grind
-how to cut nail nick.
-spinning a pin
-fitting scales.
-cutting choil after heat treat.

Slip joint making is one endless journey of asking yourself: How do I do ____(this)____? . that question then drives your whole development and equipment purchases

But anything worth doing is worth over thinking in my opinion. I love the nuances and rabbit holes to fall into. There is a lifetime of experimentation. Each knife is like a little petri dish. The problem is it takes me weeks-months for an experiment to reach fruition just to get one data point.
 
Will Power said:
Interesting pattern and a fine interpretation. Particularly like the scales, very effective. I assume this was made on spec for a client? I tend to prefer nail nicks on Wharncliffes rather than a long pull, they just suit the blade shape better in my opinion and I would make the end bolster slightly smaller than it is to emphasise the Rat-Tail.

Very promising work.

Hope you don't mind my observations, they are not criticisms just appreciation.

Thanks, Will
Click to expand...
this was my design based on some other ones out there. Not for a specific custom order. Shape from an old Ohta mostly.
slipjoints are very hard for me. I am finding that there has to be an underlying drive of "I have to make this one" to get me going. This is one I just wanted to make.

The choice of long pull vs traditional nick is currently driven by my ability and toolset. I've had some luck using a dremel cutter in my drill press for long pulls. I don't have mill yet so have to rely on stone in drill press, or chain saw sharpener with stone. I have not had best luck achieving nail nicks with those. Other choices are hot stamping which I haven't tried.

The size of the butt here became real challenge with where the blade tip sits once it is clocked at flush in all three positions. It ended up sitting too high forcing me to make the butt thicker when making the tear drop shape. Otherwise the blade tip is exposed. There are some tricks I need to work on to get that tip to sit lower. Like grinding in a divot in the spring where the kick tip would fall. That would drop the tip some.

I value and welcome the comments and insight on design.
 
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