Make a Groove in a Sword!

[@althesmith]

I just got a katana with bo-hi, made by Kanetoki in Showa 52/1977. I am amazed at the precision in the cutting of the point sections on each side.

[@gregf8167]

Your Japanese blade videos are always the best and much appreciated thank you

[@wumarNart]

0:37 Making a video on that would be a good idea. Double edge swords need some love.

[@BenButler1]

AMAZING work Walter!! Very interesting process.

[@MikeyMystery45]

I like your Hamon. Looks awesome.

[@thomasutley]

Walter, I have no idea how applicable it may be but this process reminded me of machine scraping such as we do to restore sliding ways on a lathe or mill. A Biax power scraper with the right shape of carbide tool attached might give you a good balance of speed with control to rough out grooves, especially the irregular terminations at each end. Worth researching perhaps. Also, you’d be surprised how well a woodworking router with cheap carbide bits will cut steel. It’s terribly messy and the swarf is murderous, but sacrificing a couple $15 half round bits to rough out most of the groove material on a blade like this might save you a day of hard labor. Again, maybe worth researching. p.s. Check that 1/2” groove cutter hardness if you can-I’ll wager it’s softer than your 1/4” cutter causing the chatter and fast wear. Best regards, Tom

[@NeillWylie]

You've given me some food for thought too. Thanks Thomas.

[@TheKinchaos]

That is incredible. I want to try this.

[@NeillWylie]

Walter. I have always found this process an absolute ball ache. After watching the videos of great makers like your self, I see now that this process is an absolute ball ache.

[@joey6704]

Exactly why I just use a mill machine. Doing it this way is merely for the sake of saying you did it this way. A mill would not make that curve though

[@NeillWylie]

@@joey6704 I've been dreaming of a mill for quite some time now.

[@joey6704]

@@NeillWylie Worth every penny. Check out some bench mills they have out there. A little over a grand, and they can do some pretty awesome stuff if you get the right one. I sold my old one foolishly, but I have my eyes on the Harbor Freight Central Machinery 1/2 HP Bench Mill It'll never replace a solid one ton machine, but it also has half the headache that comes with owning one too

[@mycroftholmes7003]

I never knew that hp made mills. And you can always add the bohi prior to heat treat right?

[@larrybair8074]

The master at work. What patience !

[@jachern]

Tks from Barcelona.

[@michaelroth3535]

Walter, as a Toolmaker it is a treat to listen to someone that knows what they are talking about! 🙂 And to a reply by Thomas Utely (hope I got his name right) referring to the swarf from a carbide burr or double/ single lip cutter being "murderous", ("I would rather eat worms than have it on/in me"🤓)!

[@ColdHawk]

Thanks for the interesting video. P.S. That blue chambray shirt is a classic!

[@10magicalfingers27]

I was waiting for this for ages!!!!!

[@bellumwar1342]

Love your videos

[@michaelpowell2902]

I just free handed a fuller into a crusader sword on my 2x72 wish I would have seen this a month ago. Might have saved a lot of hand sanding

[@Sebastian-ed5kt]

Same here, but with files on a 40cm wakizashi 😂😂😂 Was a 20h fun....

[@JCSalomon]

I suspect that putting the cutting edge slightly longer (maybe 47°) and lifting the cutter by the same 2° to give a bit of cutting relief, might work better.

[@The-Bladeslinger]

Do You have this tool for sale on your website or somewhere? would you consider making them to sell? Thank you

[@denniswilliams8747]

HI You may want a spirit bubble level on the tool to address the cut with the tool close to level each time. Thanks

[@robertkoontz7865]

Nice work Walter, Thanks for showing you techniques. I milled a groove in a Katana a friend made me, Unfortunately its still a club. Or executioners sword, Though I learned a lot.

[@robertodimartino7412]

Hi Walter, im sure youve answered this question before, but could you please list the top 3 materials for making these cutters from?

[@2Axiom]

Nice

[@weirdcrunkygremlin1449]

I would Love to know the weight difference!!

[@ancacandragun3159]

1:50 name of tools sir, please?

[@lad60606]

Hand carving steel with a carbide toothpick... I would go mad.

[@robertodimartino7412]

What material is best used for the cutting blade tool please?

[@wrankin]

Hey Walter, Love the videos. You need a bit of edit - 3:16 to 3:30 you repeat yourself regarding taping up and not gouging the blade. But beautiful work (which is where it counts :-). Funny thought - your comment on "don't bully the cutter, let it do its work" sound like the corrections I get with respect to a good sword cut in iaido. :-D

[@MorbidEel]

A groovy video :p

[@peacemaker-du4hz]

i wish I had your patience

[@OttoMatieque]

so what is the purpose of the groove?

[@Heikki_Finland]

Does it bother that if the sword has hard outer layer, the groove cuts it off to the soft core?

[@tonarsilverwolf6485]

toi kohta terää ei tule ottamaan osumaa niin sillä ei niin ole väliä, plus se kova alue on terän kohdalla

[@keithst.laurent5299]

Did you do that post heat treat? If you Were to do a stock removal katana would you put a curve in the blade pre-heat treat or let it curved during the heat treat say on W2 tool steel? Thanks

[@lsubslimed]

If you're quenching in water you can gain the upward curve (sori) during the quench. If quenching in a fast oil like Parks 50 you might want to add a little more upward curve than you actually want it to have while you're shaping it, since for some odd reason oil causes reverse sori, which curves the blade downward. A number of years ago I was having trouble getting a certain blade hardened and so I ended up re-quenching it multiple times in some parks 50 oil. It originally had a nicely curved belly to the edge prior to the hardening attempts, but afterward the tip dropped significantly and the edge developed a decent recurve. To get just the right amount of curve in a sword may require a bit of experience, at least to do it consistently.

[@dusanpavlovic2201]

do your swords have distal taper, did all katana have distal taper or not?

[@garrettshadbolt6443]

My God…I feel like it would be so easy to mess up and so hard to fix when you did.

[@gcardinal]

Ultra stupid question - why not use mill for the whole blade?

[@ClenioBuilder]

👏👏👏

[@dlam2864]

oh yeah, you have to do it on both sides

[@RovingPunster]

Why cut a fuller into a Katana ? Is it to lighten it, stiffen it, shift the balance point, or a combo of all three ?

[@MrZetor]

Roving Punster - Weight and aesthetics/history. Reducing material from anything can obviously only make the object weaker BTW.

[@RovingPunster]

@@MrZetor Respectfully, that is not completely true. Fullers do indeed add strength and stiffness, in much the same way the dimple on the bottom of a soda can does ... they are not an aesthetic only feature, if properly implemented (read: a properly parabolic cross section of adequate width and depth). Also, only a fraction of katanas had fullers, not all of them. In the absence of info, i'd guess the sword may have felt a little whippy/flexy, and/or the balance was a bit further forward than optimal.

[@MrZetor]

​@@RovingPunster "Fullers do indeed add strength and stiffness..." - Actually, no. For any objects with the same outer cross-sectional perimeter, a solid piece is _always_ the strongest. An object with a groove (or 'fuller'), which is commonly referred to as the 'I-beam' structure, is _significantly_ stronger than a solid piece that has the same cross-sectional _AREA_ (i.e., the same mass). This means that the fuller does not add any strength, nor stiffness, but, increasing the thickness and/or the height of the blade, _and_ then cutting the groove to bring the weight back down to the original level does indeed make the blade stronger. Granted, I suppose I didn't formulate my original comment too accurately, since weight ~= strength, but make no mistake, cutting a groove into an existing object will only make it weaker. "...the same way the dimple on the bottom of a soda can does." - I don't know whether I would actually classify the soda can dimple as an I-beam structure. I'd say it's more like a (semi) spheroid, and a sphere is obviously the strongest possible shape. Anyway, the 'dimple' has a lot more mass/material than what a straight soda can bottom would have, and thus it's not a valid comparison. "Also, only a fraction of katanas had fullers, not all of them." - I do know that not all katanas had groove(s), but do you have a source for "only a fraction"? I have always thought grooves were very common in the early periods, and even in 'modern times', maybe 10-20% of all blades had them.

[@RovingPunster]

@@MrZetor Thanks for the cogent and skillful reply. The web would benefit from more people like you. I'd like state up front that I have zero experience making knives/swords. This is mostly armchair scientific handwaving for me. That being said, I think perhaps we're partially talking past each other rather than directly to. Like you, perhaps I could have been clearer and more detailed in my OP question/comment, but I opted to try to be terse because I have a tendency to be too wordy (as you'll see below). Anyway AFAIK fullers do indeed have a positive effect on strength and stiffness - albeit with important caveats of the sort you alluded to. Consider a finished retractible metal tape measure vs an identical length of the unfinished ribbon steel used to make it - without the same cross sectional curvature, the latter is compatatively floppy/ whippy vs the former Granted the analogy is far from perfect (as you correctly pointed out), because simply altering the shape to accomplish an effect is not the same as removing mass to accomplish a similar effect because reducing mass does indeed reduce overall strength to a degree, BUT it is an oversimplification to assume the correlation is 1:1. Any loss of strength depends largely on the geometry and placement of the negative shape of material removed as well as the geometry of the material that remains ... for example, the effect of a large crosswise groove near the waist of a blade would be ruinous to both balance and strength compared to a lengthwise fuller of identicle negative volume. The net result is that, depending on geometry, it IS possible to exchange some mass for certain desirable changes in weight reduction, balance and stiffness. I believe you are absolutely correct that it is BEST to plan your design in advance to optimize the effect of a fuller, but i'm pretty sure i'm correct as well in supposing that fullers are sometimes added as a sort of post-forging correction to finesse certain things like weight, balance and/or stiffness, somewhat analagous to the way weighted pommels are used to finesse balance. That's my understanding anyway. I dont want to threadjack anymore than I already have, so i'll stop there. Cheers.

[@felixarbable]

for that last bit why not use engraving tools? would be much easier and much more accurate

[@velazquezarmouries]

But it wouldn't be as deep as a bohi

[@nicjgoss7069]

is rebar good for forging anything

[@ahiraband3939]

No it isn't. Outside of a very weird circumstance rebar is non hardenable metals, some times it's unknown pot metal at best.

[@weregecko]

not knives. it's not hardenable, but it can make nice hooks, etc, if you want to practice your general smithing skills.

[@jollyjiggler]

Some rebar will harden somewhat in water, test a small peice and see how it goes, but it IS NOT knife steel even if it does harden.

[@ColdHawk]

drunn_vevo - Tongs! There are a few good videos out on KZbin on using rebar to forge basic tongs. If you are going to work with hot metal tongs are an essential! ; )

[@reepeez]

The Korean Kagum sword has a deep groove with a 90 degree edge on it, its designed to make a distinct "woosh" sound when the cut is executed correctly, anyone looking to get a better sound out of the sword should look them up. I am going to attempt to alter the groove on my katana similar to a kaguns with a dremel as my sword is not singing to me at all.

[@AndrewJordanBladesmith]

What a cop out . The cutter used by Japanese smiths is a HISEN . Nothing like the scraper WS uses . The HISEN is a much more difficult tool to use than WS scraper . Again made up tools as opposed to the tool Japanese smith use’s . The Japanese tool is the real deal . WS version is a cop out . A HI is NOT round . It has a flat section at the bottom . Someone who has never been to japan to learn giving tuition that is not the way Japanise smiths carry out the cutting a HI . THe point cutting is entirely wrong .

[@thatguy746]

You couldn't make a popsicle stick, and this man made a beautiful sword. So I'll ask ..... Who gives a fuck? I bet old Japanese smiths didn't have milling machines either? More modern techniques are just better, get over it.

[@AndrewJordanBladesmith]

@@thatguy746 Get over what . The FACT that most ABS smith are not craftsmen but bullshitters making up techneque becouse it takes more skill . Man Merican and there big mouths . Pitty if you stood in front of me "WE ALL KNOW you'd shit your pants "

[@lindsayrobertson7801]

It is no less valuable to the blade smith to know this is a modern approach to achieving a very acceptable result. There is nothing stopping others showing the traditional Japanese techniques and tools you described. I find the tone of your comment condescending. I did not get the impression that this demonstration ever claimed to be that of a traditional Japanese sword maker.

[@paleegg3778]

the homeless take me here

[@cmanycrows8400]

Cutting a groove doesn’t strengthen the blade the way that forging a groove does for the same weight. Which was the point of the groove in the first place. Cutting a groove simply weakens the blade for what amounts to esthetic purposes. 👎🏻

[@MrBrokenwrenches]

How does cutting a fuller into a blade weaken it more than forging a fuller?

[@MrBrokenwrenches]

Do you have experience in testing the differences?

[@weregecko]

nonsense.

[@cmanycrows8400]

cody allen cutting a fuller vs forging one is weaker for the same reason that forged blades are stronger than ground blades. It’s a metallurgical fact related to crystalline grain structure and orientation. When one forges a fuller the grain structure becomes oriented to the shape of the blade verses being interrupted by a cut in the grain structure. If it helps you to think about it, a functional anologue might be laminating wood grain to follow a curve. If the grain is oriented along the radius of the curve (forged fuller) it is much stronger by weight than if the grain was say perpendicular to the radius of the curve.(cut fuller)

[@damionlowther78]

And...no. it lightens the blade and creates an I beam structure making the weight to strength ratio better. Both can be achieved with forging or cutting.