Recommendation? Stick Tang Height

[Colby L.]

Hi All -

I want to try my hand at a WA handle knife and am having trouble finding information on one dimension that I would consider pretty critical. That being what is the minimum height I should shoot for at the shoulders (on the tang side)? I prefer the ricasso (not sure if that's the correct term on a kitchen knife) to be narrower than the handle so working backwards from a 1" tall handle I get around a 3/4" ricasso which leaves around 1/2" for the tang. Is that enough for strength? I am using 0.08" stock if that plays into the equation.

 

[Hubert S.]

I mostly use around 3/8" for the tang, but have done 1/2" as well. My handles are not near as tall in the front as you plan to do, typically around 20-22mm. I also prefer to have a narrower neck/emoto/ricasso (or whatever it is called) and found that the distance between handle and choil is pretty important in order to not create a pinch point for your middle finger if you hold the knife in a, well, pinch grip. You can either go very short so the finger does not fit in the gap at all, or long enough so that it does not get pinched. For the latter option, I think around 3/4" is a good starting point.

 

[daizee]

A 3/4" tang leaves you 1/8" of material on either side of that junction with a fairly tall 1" handle. Decide if your weak point is the steel or the handle, and what kind of stresses you are looking at, and what material you plan to have at that junction.

If you HT the whole shebang and then torch-temper the tang/ricasso junction it will be quite tough.

 

[Alex Topfer]

The ones in my knife drawer are between 10mm and 18mm depending on the size of the knife. Smaller for smaller knives, and thickness is between 2mm and ~4mm.
Thickness is a factor; with a kitchen knife i would be more worried about lateral strength than vertical, and thickness is more important for that. Ideally i think it should be thicker than the blade, but that is hard with stock removal.
As far as i can see the failure mode for a kitchen knife will be lateral anyway, if someone has put that much stress on a 2mm thick kitchen knife they are doing something wrong. you probably want the handle to crack if they are doing that.

The shoulder there only needs to be enough to hide the join, mechanically it doesn't even need to exist. For your one above I would do 1.5mm (~1/16) shoulders on each side, with the tang ~15mm (~5/8) wide at the start.

If you want to get mathematical (who doesn't) i found this:
View attachment 1613241
based on this you will get similar stress concentration based on a 1.5mm radius fillet with a 15mm tang as a 3mm radius fillet with a 12mm tang. looking at this, you don't want to get to a fillet radius/height below 0.1 and you want to keep height1/height2 as close to 1 as possible.

tldr: i think it should be it taller. i would do ~15mm / ~5/8

 

[Colby L.]

I mostly use around 3/8" for the tang, but have done 1/2" as well. My handles are not near as tall in the front as you plan to do, typically around 20-22mm. I also prefer to have a narrower neck/emoto/ricasso (or whatever it is called) and found that the distance between handle and choil is pretty important in order to not create a pinch point for your middle finger if you hold the knife in a, well, pinch grip. You can either go very short so the finger does not fit in the gap at all, or long enough so that it does not get pinched. For the latter option, I think around 3/4" is a good starting point.

Thanks for the reply and good insights on the gap before the choil. I prefer that distance to be on the short side so I'll be sure to keep an eye on it as build the knife. What thickness of stock are you using with the 3/8" tangs?

 

[Colby L.]

A 3/4" tang leaves you 1/8" of material on either side of that junction with a fairly tall 1" handle. Decide if your weak point is the steel or the handle, and what kind of stresses you are looking at, and what material you plan to have at that junction.

If you HT the whole shebang and then torch-temper the tang/ricasso junction it will be quite tough.

Thanks! I was thinking I'd have 1/2" tall where the steel enters the handle. More on that as well as the stresses induced below...

 

[Colby L.]

The ones in my knife drawer are between 10mm and 18mm depending on the size of the knife. Smaller for smaller knives, and thickness is between 2mm and ~4mm.
Thickness is a factor; with a kitchen knife i would be more worried about lateral strength than vertical, and thickness is more important for that. Ideally i think it should be thicker than the blade, but that is hard with stock removal.
As far as i can see the failure mode for a kitchen knife will be lateral anyway, if someone has put that much stress on a 2mm thick kitchen knife they are doing something wrong. you probably want the handle to crack if they are doing that.

The shoulder there only needs to be enough to hide the join, mechanically it doesn't even need to exist. For your one above I would do 1.5mm (~1/16) shoulders on each side, with the tang ~15mm (~5/8) wide at the start.

If you want to get mathematical (who doesn't) i found this:
View attachment 1613241
based on this you will get similar stress concentration based on a 1.5mm radius fillet with a 15mm tang as a 3mm radius fillet with a 12mm tang. looking at this, you don't want to get to a fillet radius/height below 0.1 and you want to keep height1/height2 as close to 1 as possible.

tldr: i think it should be it taller. i would do ~15mm / ~5/8

Thanks for the reply! That chart is interesting. It seems to be a bit more for axial loads while the loads at the tang joint are more flexural in nature.

Since you opened the mathematical flood gates I ran some numbers and did a little testing.

I am having a hard time finding a yield strength for 52100 that seems realistic so I based everything below on a yield strength of fy = 36 ksi (based on the very commonly available A36 structural steel).

In terms of lateral strength - I have a +/-6" blade utility knife I made out of .0625" stock. It is 1" tall at the handle. It seems plenty robust in the lateral direction, so I used it as a basis for design. To get an equivalent section modulus (strength) with my 0.08" stock I need to have the tang be about 0.60" tall. At that height it actually has a 28% better moment of inertia (resistance to flexing).

The theoretical vertical strength with the 0.6" tall tang would allow me to put about 25 lbs of pressure 7" out from the front of the handle. I just got the bathroom scale out and grabbed a chef's knife and pushed the spine, near the tip, into the scale. It took me using both hands and pushing with nearly everything I had to develop 25 lbs of pressure that distance from the handle. I doubt a knife would ever see that much force.

I also happen to already have the knife in question rough cut out and the tang sits at about 0.7" tall. I clamped it in my vice and hung a 25 lb weight off the end of the blade and it handled it no problem.

So all in all I think 0.6" tall is plenty strong based on the yield strength I assumed. I'll shoot for that, perhaps slightly less, and just use smaller shoulders.

TLDR - I'm going to go with about 0.6" for tang height.

 

[Hubert S.]

Thanks for the reply and good insights on the gap before the choil. I prefer that distance to be on the short side so I'll be sure to keep an eye on it as build the knife. What thickness of stock are you using with the 3/8" tangs?

I use mostly around 2mm, but have made anywhere from 1.5mm to 3mm knives with the same tang height. When I first started making knives, I thought the tangs had to be taller as well, but everybody suggested using 3/8". I usually use a dowel to put the handle together and 3/8" and 1/2" dowels are readily available and I have longer drill bits in those sizes. With a 1/2" dowel, you have to be pretty well centered in order not to grind into it when you shape the handle, so I prefer 3/8". I cannot imagine using a 0.6" dowel, that is close to the width of my handles in the front. Lately, I have made a few knives without dowels (either frame style or by cutting the blank in half, routing out a channel and then gluing the halves back together). That would make it easier to leave more meat at the front and then taper towards the back, but I just cut the recess for the tang with a 3/8" end mill and open up the front a bit for the fillet at the shoulders.

FWIW, I have not had any issues with a 3/8" tang, even when batoning through some stubborn foods with the aid of a rolling pin. I hope some more experienced makers will chime in.

What kind of knife are you making and how big is it?

 

[Alex Topfer]

It sounds like it's not too vital unless you're getting into cleaver territory

 

[Colby L.]

I use mostly around 2mm, but have made anywhere from 1.5mm to 3mm knives with the same tang height. When I first started making knives, I thought the tangs had to be taller as well, but everybody suggested using 3/8". I usually use a dowel to put the handle together and 3/8" and 1/2" dowels are readily available and I have longer drill bits in those sizes. With a 1/2" dowel, you have to be pretty well centered in order not to grind into it when you shape the handle, so I prefer 3/8". I cannot imagine using a 0.6" dowel, that is close to the width of my handles in the front. Lately, I have made a few knives without dowels (either frame style or by cutting the blank in half, routing out a channel and then gluing the halves back together). That would make it easier to leave more meat at the front and then taper towards the back, but I just cut the recess for the tang with a 3/8" end mill and open up the front a bit for the fillet at the shoulders.

FWIW, I have not had any issues with a 3/8" tang, even when batoning through some stubborn foods with the aid of a rolling pin. I hope some more experienced makers will chime in.

What kind of knife are you making and how big is it?

I am making a santoku style knife with a 7" blade, just under 2" tall at the heel. It sounds like my 1" tall handle may be too much. I am thinking Ill just rough out a handle this weekend with some scrap lumber and decide what feels good in hand. Based on your experience I should be able to get away with a smaller handle, resulting in a shorter tang. Ultimately the knife is intended for my kitchen so I am not too concerned about experimenting a bit with this one. If you are going 20-22mm tall for your handles what widths are you typically aiming for?

 

[CallumRD1]

I’m no expert, but I’ve standardized on 1/2” tall by 3” long for my wa handle tangs, usually in 0.084” stock. I affix my handles with beeswax so they’re removable and interchangeable. Having all my tangs identical makes that a very useful system. If I create a new blade I want to start using, I can take my favorite handle off an older knife and put it on the new one. Or if I want to refinish an handle for whatever reason, I can.

Edit: I also tend towards very thin and fine cutting knives that aren’t subject to abuse. I’d never baton them though a vegetable like someone mentioned above, so for my application this method is sufficiently robust. I’d never use this technique on a cleaver, for example.

 

[weo]

Decide if your weak point is the steel or the handle

This is the thing I think about.
As was mentioned above, kitchen knives shouldn't be subjected to the same abuse as a camp knife or EDC, so tang strength, while important to a point, isn't something I fret over. I try to have a shoulder on all 4 sides of the tang, so on thinner knives, the tang is even thinner. I recently did a smaller paring knife where the neck of the blade was 0.075" thick and the tang was 0.055"thick and don't notice any flex in the tang or handle.

 

[Hubert S.]

I am making a santoku style knife with a 7" blade, just under 2" tall at the heel. It sounds like my 1" tall handle may be too much. I am thinking Ill just rough out a handle this weekend with some scrap lumber and decide what feels good in hand. Based on your experience I should be able to get away with a smaller handle, resulting in a shorter tang. Ultimately the knife is intended for my kitchen so I am not too concerned about experimenting a bit with this one. If you are going 20-22mm tall for your handles what widths are you typically aiming for?

The width is around 16-17mm in the front, 19-20mm in the back. A prototype from scrap is a good idea, I've made a few from construction lumber myself. I typically use a tang around 3.5" long, give or take.

 

[Hubert S.]

I’m no expert, but I’ve standardized on 1/2” tall by 3” long for my wa handle tangs, usually in 0.084” stock. I affix my handles with beeswax so they’re removable and interchangeable. Having all my tangs identical makes that a very useful system. If I create a new blade I want to start using, I can take my favorite handle off an older knife and put it on the new one. Or if I want to refinish an handle for whatever reason, I can.

Edit: I also tend towards very thin and fine cutting knives that aren’t subject to abuse. I’d never baton them though a vegetable like someone mentioned above, so for my application this method is sufficiently robust. I’d never use this technique on a cleaver, for example.

That sounds like a neat system. How do you construct your handles? When I use the dowel method and bed the tang with epoxy, the handle is pretty tight and I don't think my tangs are consistent enough where I could get another one in there. I made two frame handles at the same time earlier this year, and those were interchangeable with the two blades I made for them, but they did have a bit more play than the handles with the bedded tangs I've made.

As a side note, I do not baton knives through veggies on a regular basis, and it sounds a bit more violent than it actually is. Whenever I make Korean barbecue, I cut 3/4" discs of corn, and some cobs are pretty tough to cut through, so I use a few taps with a rolling pin or wooden mallet. I haven't had an issue even with very thin knives, they actually work a lot better for this than thicker knives.

 

[CallumRD1]

That sounds like a neat system. How do you construct your handles? When I use the dowel method and bed the tang with epoxy, the handle is pretty tight and I don't think my tangs are consistent enough where I could get another one in there. I made two frame handles at the same time earlier this year, and those were interchangeable with the two blades I made for them, but they did have a bit more play than the handles with the bedded tangs I've made.

As a side note, I do not baton knives through veggies on a regular basis, and it sounds a bit more violent than it actually is. Whenever I make Korean barbecue, I cut 3/4" discs of corn, and some cobs are pretty tough to cut through, so I use a few taps with a rolling pin or wooden mallet. I haven't had an issue even with very thin knives, they actually work a lot better for this than thicker knives.

The hidden dowel method is, in my opinion, by far the best way to make a hidden tang wa handle. I drill a 1/2" blind hole in the handle material and the ferrule, leaving about 1/8" of material in the bottom off the ferrule. I then use some small drills, a knife, and a needle file to shape the slot for the tang. I take a 1/2" dowel and slit it to about the width of my tang using a table saw, glue it in the handle material, glue the ferrule on top, and then shape the handle. With this method the only part of the handle that is precisely fit to the tang is the very end of the ferrule. It's very easy to get a really good looking handle without spending hours trying to drill/cut/shape a slot through the entire handle. I have a dummy tang made from a piece of 4130 that I heat up to ream out the finished handle. At that point it's a very snug fit on the tangs. Some of my blades I've used for extended periods without any further attachment beyond the friction but most I set with bee's wax. I can gently reheat the knife to soften the wax and remove the blade from the handle. Here are some photos illustrating it:

https://imgur.com/a/8Sbvpx1

 

[ChristoDart]

Very nice! Thanks for the explanation on your process. When you say you use that piece of 4130 to ream out the finished handle is that to get the glue out of the slot? How do you keep large amounts of epoxy from pooling at the bottom of the slot in the dowel during glue up? Thanks.

 

[CallumRD1]

I don't use a huge amount of epoxy; enough to very thinly coat the surface of the dowel and a little in the hole, but not more than that. The slot in the dowel is at least a half inch deeper than necessary to fit the 3" tang so I don't worry about some epoxy accumulating there. I do the glue up in two stages, one gluing the dowel into the body of the handle and the second gluing on the ferrule. That allows me to use a subtle wedge to ensure the dowel doesn't close during the initial glue up (see photo 3). The hot 4130 dummy tang is to clean out residual epoxy that may be in the slot and to burn back anywhere that the wood may have been slightly too tight. I'll usually ream with the dummy tang at a minimal heat a few times and only get it super hot if I need to move a fair bit of material. I always err on the side of a tight fit over a loose fit.

 

[ChristoDart]

Excellent explanation. Thank you.

 

[Colby L.]

Thank you all for the reply and advice! As always I am amazed and grateful for the amount of knowledge you all have and are willing to take the time to share. I'll report back once I'm done with the knife!

The width is around 16-17mm in the front, 19-20mm in the back. A prototype from scrap is a good idea, I've made a few from construction lumber myself. I typically use a tang around 3.5" long, give or take.

Thanks. I'll see what feels good with a dummy handle this weekend

 

[Colby L.]

Thank you all for the reply and advice! As always I am amazed and grateful for the amount of knowledge you all have and are willing to take the time to share. I'll report back once I'm done with the knife!