What I'm working on

Flat Grinding Rundown of a Tyrant Bolo.

Here's a quick overview of how I do a flat grind on a very big blade. I'd like to add that I'm not very naturally talented at grinding and am probably not the best person to learn from. I'm currently working towards getting bevels rough milled for perfect consistency and precision. From there, I can finish by hand with much greater accuracy. The tolerances I want to achieve are difficult to do by hand and requires years of practice, trial and error.

So here goes.

The blade pictured is the Tyrant Bolo. Its a massive blade and will be a challenge to grind. Its a 17.5in blade and is 3 inches wide at the sweet spot. Starting weight is just over 42 ounces. The larger and heavier a blade is, the more difficult it is to grind. This one is made from 52100 and is going to be hard ground. For low alloy steels like 52100, I prefer to hard grind because I don't like finishing the blade twice. If you grind a blade before heat treat, the bevels must be ground and finished to at least 120 grit to avoid stress risers during quenching. If you were to just hog off steel with a 50 grit belt and sent it to HT, the phase change the steel undergoes in the quench will almost certainly cause cracks to propagate along the 50 grit marks. Additionally, you cannot grind an oil hardening blade to its finished thickness before HT because, the edge will be too thin and will warp during the quench.

With an air hardening steel like 3V, you can completely finish the blade before HT. Most air hardening steels can be taken down to .020-.10 edge thickness before heat treat which is the finished thickness for most blades.

With that in mind here is the grinding process.

First, I start by painting the edge of the blade with dykem layout fluid. This is a very necessary process and I never grind a knife without it. Some guys will paint the entire blade to help them visualize grinds but typically just stick to the edge.





Next, using this nifty tool, I scribe the center lines. If you are going to make knives, this is one of the most important tools you can have. Getting the edge centered is of the utmost importance if you want even bevels.



To use this tool, just decide the edge thickness you want to stop at, deduct it from the total stock thickness and divide by two. I've crudely illustrated this process on the whiteboard. You may also want to keep in mind the actual thickness of the scribe line itself, depending on whether you want to leave the line intact or if you want to grind the line away. The line itself is about .003 thick. I like to grind the line away to I subtract the line thickness. For this Bolo made from .1875 thick steel, I need to adjust the scribe to .079. Then I take away .003 for a finished line height of .076. Taking into account the thickness of the line is not that important but it is something I like to do.



To scribe, pick a perfectly flat, square surface. You really want to use a granite precision block but I don't have one so for now my bandsaw table does the trick. Drag the scribe along the edge of the blade and then flip over and repeat. Voila, you have a perfectly centered edge.





Now its time to start hogging off material. I begin by using a 10in wheel to grind the edge down to the scribe mark. For this I use an old 50grit belt. The sharp edge on the blank can knock all of the grit off of a new belt. I quench every pass and keep the blade cool. Here is a comparison between an old belt and a new belt. I use Ceramic Cubitron belts from 3M. They work very well and last a long time.

On the wheel you will establish your initial bevel as well as the plunges. You have to get this step right or else your blade will be ruined. No pressure.



Looks good so far.



After the meat on the edge has been hogged off its time to go to the flat platen and begin the flat grind. For flat grinding I use a fresh 50 grit belt. Sometimes I will use a 36 grit if it really thick stock.



For the flat grind, I just take the blade to the grinder and begin slowly taking off steel each pass and making the grind higher.
This is where the jankiness in your grinding technique will come out. All of us have differences and imbalances between our right and left sides and they will manifest in unevenness in your grinding. The goal is to pull the blade straight across the platten with consistent pressure and a consistent angle. Much easier said than done, especially on a blade this size. This is the part of grinding that takes years and years of practice and hundreds of blades to get right. I'm still not there and probably never will be.

Bevel coming along



After the bevel is established with the 50 grit belt and you get it to the correct height its time to start the finishing process. I jump to either an 80 grit belt or a 120 grit belt next. For this blade I went with the 80 grit just to make sure there are no lingering 50 grit scratches. The last thing you want it to have your bevel finished out to 280 grit and find a 50 grit scratch lurking under a nice finish.

For belt jumps you never want to do more than double the grit, lest you risk leaving the lower grit scratches visible. My typical belt progression for 52100 is 50, 120, 180, 280, 360. For a machete, if all is going well I can sometimes leave out the 280 and go straight to the 360 finish.

For grits 50-120 I use ceramic cubitron belts from 3M. For 180-360 I use Trizact finishing belts. They have a cool structured surface and leave a nice finish.

On this blade I'm adding in some extra steps to make sure the finish is consistent. One of these steps is the scotchbrite belt. These are specialized finishing belts and they are a godsend. They help blend together grit marks and leave a nice even finish.

Here is a picture of the blade after being finished to 180 grit and hit with the scotchbrite belt. From here, the blade will get a long soak in some acid to remove the decarb on the flats and then I will finish the bevels with the 280 grit and 360 grit belts.

 

Its definitely alot of hard work making a blade by hand, and I'm starting with a water jet blank and doing stock removal! Forging is a "whole nother level" of labor. I'm exciting to be moving more towards CNC work so I can spend less of my time in front of a grinder hogging off steel and more time perfecting designs, testing, and just generally being creative. Not to mention the sheer amount of design features you can incorporate that are impossible or very difficult to do by hand. There's some seriously cool stuff coming soon that I've been wanting to make for years, and only now with the help of CNC am I able to bring it to fruition in a small scale production format.

 

I'm still doing logistics and haven't made any final decisions yet. Its going to be a challenging model to produce and the production model will be CNC machined with a fuller and then finished on the grinder by hand. I'm also planning on doing a traditional stick tang and having a machined handle that will look like a single solid piece but will be two scales that seat on the tang and will be attached by screws or pins and glue.

Right now the plan is to do a handful of test pieces in something like 80CRV2. After testing the final production models will be either 3V or possibly Z-Tuff. Alot of it is just going to depend on price, availability of the steel, and cost of tooling. Using a premium PM steel will make them more expensive but its already going to be a very expensive blade so I might as well use the best steel possible.

 

I talked to a guy at Zapp a week or so ago and he seemed to indicate its a good steel. I haven't tested it yet and would have to get a test piece before committing to it but it looks composition wise like it would be a solid performer. What really is exciting to me is the hardness it can obtain. Maybe they are getting enough increase in edge retention from Z- wear without much loss in toughness that Z-tuff may not be the best trade off? Just speculation but I know they are pushing Z wear to be a competitor to 3V which is one of Zapps biggest rivals.

Z wear has been great so far for me and I think it would be good in a big blade. My only worry is the grinding as its harder to finish than 3V. Thats another material to keep in mind. Basically I will be using a high performance PM steel but I will need alot of it and in the right size stock and for a good price so it may come down to that.

Things like Z wear and V4E will be kept in mind when the time comes around for material selection. If I could score a sheet of v4E and it doesn't present any major tooling issues like work hardening I would 100% go that route. However Bohler is hard to work with alot of the time.

 

They are much more willing to work with you if you are buying a full sheet but even then its hard to get through to someone who knows what they are talking about and can help. My experiences with Zapp have been great so I'll probably be working with them more in the future.

Calmax looks like it would be super tough but its kind of low on carbides. I wonder if it would be worth the increased cost over something like 80CRV2 or L6?

Ill be contacting Bohler here soon to see if they have any V4E available for the Tyrant Bowie. That will be the next big blade Ill be making. The new scales are being made now and I'll be getting the blanks water jetted and milled out over the next month or two. Right now I'm planning on 3V but 4VE would be icing on the cake.

 

Your conclusions about edge retention during chopping is similar to what I've experienced myself. Abrasive wear is the last mode of edge loss when chopping. Rolling and chipping are the primary mechanisms through which edge loss occurs. Abrasive wear is really only a major factor when making slicing cuts and to some degree push cuts. For a big chopper, a high hardness steel with great toughness will last the longest.

This is the Tyrant Bowie. There will some jimping added along the spine and butt of the tang but this mock up is close to what the finalized version will be. The blade height is 2.5 inches at the wides point and just over 13.5 long. Steel will be .275-.300 thick. Truly one Bowie to rule them all.

Here's the new handle it will be sporting. Its a simple, straight style handle that is a little smaller than the fell beast handle. Its designed for power chops but should be small enough for knife tasks as well vs. the fell beast handle which is a pure chopping handle. The new scales will also have a hidden lanyard. First run will be Terotuf and possibly some G10.

 

The Kukri is going to be big but I want it to be a faithful yet modernized rendition of the blade style. I have no idea what the final blade weight will be but the tall bevel, fuller, and stick tang will cut out a big amount of weight. The scales will be made with both materials most likely. G10 is out of the question due to weight and material cost/ availability. Ill have to be using at least .500 thick sheets to get them to seat on the tang and still be thick enough to get the curves of the handle right.

 

Thanks,

I got some help on the handle design from a good dude

 

I've been playing around with some mid sized knife designs. This wouldn't hit production until after the Tyrant Bowie and Bush Waki but in the mean time I'd like to get it protoyped and fine tuned. Personally I'm not a fan of mid sized blades but this design could be practical as an all in one style blade that can chop. It utilizes the same scales as the Tyrant Bowie.

The next run of machetes is also being worked on and will be 52100. Those should be in the shop in about a month. I'm introducing a couple new Fell Beast prototypes in an effort to provide a wide variety of styles.

The True Grass machetes will be available around that time was well.