Manji Sai for Nunte Bo

[Noah M Legel]

Hello everyone,

I live in Phoenix, AZ and have done a little bit of forging, but not much. I've forged a knife with Tai Goo's help, and started forging a tanto with the help of Cris Anderson (C. Anderson if you've seen him on other forums), but that's pretty much it. I will be doing some forging at a friend's place (I live in an apartment, so that's really the only way I can get to forge is when I'm invited) at the end of the month and I was hoping to try and forge a manji sai like the iron one below:

I'm not entirely certain how to go about doing it because of the tines. He thinks forge welding a crosspiece onto the main body of the sai would work best, but I've heard other suggestions of splitting a wide 1/2" bar and bending the tines out that way, and another suggestion of drifting an eye in the crosspiece and sliding it onto the shaft of the sai, then upsetting the shaft to hold it in place. Has anyone here forged sai before? Any suggestions? Thanks!

~Noah

[HWooldridge]

Split and forge is by far the most reliable way to get that shape - especially if you are not adept at forge welding.

[Noah M Legel]

Split and forge is by far the most reliable way to get that shape - especially if you are not adept at forge welding.

Thanks for the advice! I just discovered that my friend's forge only has a 4" opening, which will hamper this project if I were to try splitting it, but that is what I had originally thought we could do. We will probably end up welding the tines on, either MIG weld or forge weld, as he can do either, although I would certainly prefer it to be forge welded. I was just wanting to see if anyone had any other options that we hadn't thought of, or if there were any suggestions on how to go about forging it

[pkrankow]

How wide is it when finished?

is there a reason you can't split , draw out and form each section using convenience bends then take one final heat of the junction to bend the parts to final position?

Phil

[HWooldridge]

I agree with Phil. A 4" opening is plenty big enough if you do all the work with the tines lying more or less parallel then bend them out on the last heat.

BTW, I built a hand sai for the boys to play with years ago but it turned out large and unwieldy because I started with 3/4" stock. I've never handled an original but think a more comfortable size to actually use would be closer to 3/8".

[Noah M Legel]

I agree with Phil. A 4" opening is plenty big enough if you do all the work with the tines lying more or less parallel then bend them out on the last heat.

BTW, I built a hand sai for the boys to play with years ago but it turned out large and unwieldy because I started with 3/4" stock. I've never handled an original but think a more comfortable size to actually use would be closer to 3/8".

The reason that will not work is because I will be using this in my martial arts training and it will actually be coming into hard contact with other weapons, so the steel will need to have a spring temper. I don't think I could do one heat to bend the tines into their final position AND heat treat it As far as the thickness goes, the junction of the tines and main shaft is about 1/2" and tapers down from there.

[pkrankow]

The reason that will not work is because I will be using this in my martial arts training and it will actually be coming into hard contact with other weapons, so the steel will need to have a spring temper. I don't think I could do one heat to bend the tines into their final position AND heat treat it As far as the thickness goes, the junction of the tines and main shaft is about 1/2" and tapers down from there.

Well, if you weld it or upset the cross bar in you won't be able to heat treat it either... Anyways you want to do no manipulation in the heats for heat treating.

There are alternatives for heat treat. You can build a charcoal fire for the one session, or see if someone else in the area can help with heat treat.

What material are you using?

Phil

[Noah M Legel]

Well, if you weld it or upset the cross bar in you won't be able to heat treat it either... Anyways you want to do no manipulation in the heats for heat treating.

There are alternatives for heat treat. You can build a charcoal fire for the one session, or see if someone else in the area can help with heat treat.

What material are you using?

Phil

I suppose that's true--I hadn't really thought of that! I'll either be using rebar or coil spring, depending on how thick the spring is

[pkrankow]

Rebar being mystery metal may not be a good choice. I would stick to the coil spring.

What are the typical finished dimensions of a sai?

It would take some effort but upsetting the center of the bar to have enough metal to form the cross bar is an option. The challenge is keeping the bar straight as you upset it.

Phil

[Noah M Legel]

Rebar being mystery metal may not be a good choice. I would stick to the coil spring.

What are the typical finished dimensions of a sai?

It would take some effort but upsetting the center of the bar to have enough metal to form the cross bar is an option. The challenge is keeping the bar straight as you upset it.

Phil

Ray Richard has had a lot of good luck using rebar for spears and even knives, so I was still considering it if the coil spring is too thin. The dimensions vary, but a manji sai is roughly 1/2" thick at the junction of the tines and main shaft and tapers down to about a quarter inch at the ends which is then filed to a point. It would be about 5" wide and 16" to 22" long, depending on the measurement of my forearm which I haven't measured yet :P

[Frosty]

Once you're finished forging you can bend the final shape then heat treat it in a BBQ over charcoal briquettes with a hair dryer for blast. You're only looking for critical heat and any additives in the briquettes won't be a factor, just break them up to grape size +/- to help consume all the oxy in the blast and reduce scaling on your sais.

Frosty the Lucky.

[Steve Sells]

I missed something, WHY cant one heat treat after welding in the cross pc's ?

Steve Sells, Shihan
No Tora Ryu Jujitsu, among other things

[pkrankow]

I missed something, WHY cant one heat treat after welding in the cross pc's ?

Steve Sells, Shihan
No Tora Ryu Jujitsu, among other things

Dimensions of the finished part and the opening for the forge.

[Noah M Legel]

Dimensions of the finished part and the opening for the forge.

After handling a traditional nunte bo at my dojo again last night, it would seem that I was wrong--modern tournament nunte bo are that wide, but the traditional design is narrower. I didn't get the opportunity to measure it but it seemed to be 4" wide at the elbows of the tines, and possibly slightly narrower than that. Looks like I may be able to heat treat it in that forge without as much difficulty as expected!

[ThomasPowers]

Note---traditional ones may be sized for smaller hands.

Historical ones would almost certainly not be made of a medium to high carbon steel. (if used against blades there is a virtue in having the blade nick the guard as it gives you more control of the blade in a twist movement.---but yes they would have to be replaced more often.)

I have 1/2" and 5/8" coil springs from autos/pickups in my scrap pile and also 1.25" coil from earth moving equipment and one slightly smaller from a train car.

Do preheat and full penetration welds if using modern welding methods. The heat treating afterwards should cover any postheat

[ThomasPowers]

PS: be sure to temper over 500 degF to have a tough rather than hard and brittle item!

[HWooldridge]

Note---traditional ones may be sized for smaller hands.

Historical ones would almost certainly not be made of a medium to high carbon steel. (if used against blades there is a virtue in having the blade nick the guard as it gives you more control of the blade in a twist movement.---but yes they would have to be replaced more often.)

Many years ago, I knew an Oriental gentleman who had a nice collection of antique Japanese weapons; I was very fortunate that he let me inspect them on occasion. In addition to some fine swords and knives, he also had some esoteric items such as a couple of chain weapons that I didn't recognize, shuriken, etc. They were valuable collectibles so there was no thought of conducting any spark testing or other mechanical evaluation but visually, every item that was not specifically made for cutting appeared to be made from wrought iron. I suspect carbon steel was so valuable that it was only used where necessary.

In addition, the finish on the cutting implements was much better than the iron weapons, which often looked like they had been finished with a flatter or smooth faced hammer.

[mrnewberry]

Ray Richard has had a lot of good luck using rebar for spears and even knives, so I was still considering it if the coil spring is too thin. The dimensions vary, but a manji sai is roughly 1/2" thick at the junction of the tines and main shaft and tapers down to about a quarter inch at the ends which is then filed to a point. It would be about 5" wide and 16" to 22" long, depending on the measurement of my forearm which I haven't measured yet

Raymond Richard uses 60 grade rebar. Not all rebar is created equal.

[Noah M Legel]

Note---traditional ones may be sized for smaller hands.

Historical ones would almost certainly not be made of a medium to high carbon steel. (if used against blades there is a virtue in having the blade nick the guard as it gives you more control of the blade in a twist movement.---but yes they would have to be replaced more often.)

I have 1/2" and 5/8" coil springs from autos/pickups in my scrap pile and also 1.25" coil from earth moving equipment and one slightly smaller from a train car.

Do preheat and full penetration welds if using modern welding methods. The heat treating afterwards should cover any postheat

PS: be sure to temper over 500 degF to have a tough rather than hard and brittle item!

Since this manji sai is going to be mounted to a bo staff for use as a nunti, the hand size isn't too critical for me. As for the temper--I was hoping to get a springy temper out of it so it doesn't get bent up from hitting other weapons (sai and bo)

Raymond Richard uses 60 grade rebar. Not all rebar is created equal.

Thanks for that, Allen--now that you mention it I think I vaguely remember him mentioning something about that, either at Tai Goo's Hammer-in or on the KD forums