Newbie- grind and hone angles

G

GMBlades

Joined
Apr 27, 2014
Messages
70
Hi folks
My first post. Great forum, been reading it for a couple months now!

Made a beautiful charcoal forge to anneal my file knife and apparently it worked too well. Too much air flow and ended up melting tip off. Got through the first quench ok but went for 2 and then ruined it. Oh well ... ground it down a little smaller and finished the blade today complete with a blue and black jean micarta handle.:)
Had air flow from hair dryer on low so maybe incorporate a dimmer switch as well for the next one.

My question is regarding the above mentioned angles. If you stuck to 20 deg grind and 30 hone then the actual grind angle only travels about 3/16 or 1/4 inch up the blade towards the spine. It kind of looks silly. On my first attempt, (the one that I melted) I just went with what looked good, and that was about 5/8 inch up, but without doing any calculations that like about a 8 deg angle. so in actuality there would have only been the cutting edge grind really.

Is there such a thing as a tripple grind? Like the 8 deg then the 20 and finally the 30?

Just wanted to try a couple before my 1084 is delivered.
All comments and suggestions will be greatly appreciated.

Grant
 
Welcome to Shop Talk. Filling out your profile will help us a lot. All the info - age, location, occupation, hobbies and interests - helps us give answers specific to your situation.

The main bevels are ground/filed to the height you want. The angle does not matter. You want them to be acute enough so the blade doesn't "wedge" in cutting. About 7° inclusive COLOR="#FF0000"]*[/COLOR] is normal. After the blade is sanded and hardened, the final edge is put on. This is the angle you see mentioned when reading about a blade. A normal user knife has about 30° inclusive angle. That means each side is sharpened at 15°.

The best blades for cutting/slicing are FFG - Full Flat Grind. That is when the main bevel goes all the way from the edge to the spine. When the bevel is finished and ready for hardening, the small flat along the edge should be about .020" wide. After hardening and finish sanding, the edge should be about .005-.010" wide. This is sharpened to make the sharp edge as the very last step. If you sharpen it earlier to test the edge after HT, dull it back a bit before finishing the blade. A sharp edge while sanding and installing the handle is an accident waiting to happen.

* People usually have no idea how small the main bevel angle actually is. The sharpening angle is many times greater. A few examples:
1X.125" utility blade FFG is 7.2° inclusive ( 3.6° per side) is sharpened with a secondary bevel at 30° inclusive.
1.25X.125" hunter blade FFG is 6° inclusive ( 3° per side) is sharpened at 25° inclusive.
2X.250" bowie FFG is 7.2° is sharpened at 30-40° inclusive.
1.5X.185 camp chopper FFG is 7.2° and sharpened at 40° inclusive
1X.060" fillet blade FFG is 3.6° is sharpened at 15-20° inclusive.
1.5X.125" Yanagi-ba with a .750" high single sided bevel is 9.6° and is beveled to the final edge. A tiny microbevel at 15° is added to strengthen the edge.
A 1.25X.125" blade with a Scandi grind has a 1/2" high bevel at 14.2° inclusive. The bevel on a scandi is ground to the edge and has no secondary bevel. A tiny microbevel is sometimes added.
 
Thank you bladsmth. You answered my question and then some, Great information for many. Give me a couple days and I'll post a few photos.;)
 
Thank you bladsmth !!!

Been researching bevel angles myself. What a great wealth of knowledge you are !!!
Other than Rowe's bubble jig or stationary jig, how do I get these bevel angles correct to these specs while on the grinder?
Troy
 
You don't have to get them "correct". If you scribe the centerline on the blade edge area of the profiled knife, you just grind the bevels from spine to the scribed lines.


Now, if you don't know how to scribe the centerline, here is how:
You can buy a edge scribe tool for $20-50...but a cheap drill set will do the same thing.
First, sand the blade edge area of the profiled knife blank smooth with 220 grit paper so it isn't scratched up. It should be smooth and fairly flat. It doesn't hurt to sand and scribe the spine, too.
Take a drill bit that is about .040" smaller than the metal thickness and clamp it to something flat and smooth. A piece of steel, a scrap of countertop, a granite surface plate, or even a flat piece of hardwood will do.
Lay the knife blank on the flat surface and scrape the edge along the drill bit tip. It will scribe a line just below the center. Flip over the blade and scribe again. You now have two parallel lines on each side of the center which are about .040 apart. You will file/grind the bevel until it meets these lines. By picking a drill bit the right size, you can make the spacing what you want.

Example - For 1/8" steel, use a #44 bit ( .086") and the lines will be just about exactly .040" apart.

Once the filing reaches the lines, switch to sandpaper backed with a hard and flat backing block. Aluminum, steel, or hard wood will work as a backer.After sanding, the edge should be about .030"...which is jus righ for HT. It can be a tad narrower, but don't go below .020" on carbon steel ( stainless can be .010 without problem)
 
I am following instructions !!!

Have my double scribe lines and took my first bevel down to .04 (haven't hand sanded yet).
My question is about the front taper. I started my taper at the front of the ricasso and have worked
my way down to the tip. What would be a "correct" gradual taper measurement? I know there isn't
a correct answer but is there a declining number or a percentage ?

Here is where I am at now:

Ricasso - .180 1/2 blade - .165 start swedge - .153 tip - .075

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Thanks for the help and education,
Troy
 
Ok.
Melted my first knife attempt in the forge but as promised here is a pic of my second attempt.
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I'm by no means an expert as I've just started making knives also but here is what my first blade looked like when I started it last weekend. I first used a 10 degree for the start and worked that to a line I put about 1/3 of the way up the blade as a filing guide then I reblued (layout blue) the filed area, lowered the angle (which I wrote down for doing other side) and continued filing bevel until I was just leaving a VERY SLIGHT witness of bluing on the bevel all evenly along the cutting edge. I continued doing this process until I achieved the desired bevel. I also made sure I didn't not violate the centerline I scribed along cutting edge before filing. In the last picture is my finished pre heat treat blade. During this process I never violated that edge and ended with a .025" pre heat treat cutting edge. The material started out .125" O1.

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bladsmth said:
Example - For 1/8" steel, use a #44 bit ( .086") and the lines will be just about exactly .040" apart.
Click to expand...
Ok, I have a really stupid question, I know it is, but I'm asking anyway, if my steel is .110" it would be slightly thicker than the 1/8th" steel when scribed it would be a bit thick at the edge (opposite of my goal of having a slicey li'l blade) so if I used a #46 would that be ok, or should I go with the 3/32s?

Here's the WIP thead that I been updating.
 
The scribed lines are just a guide to establish the edge in the center. If the lines are too close together, or just one line, you may obliterate it in filing and the edge may wander in a sinuous line. This is prevented by establishing it straight in grinding/filing to the two reference lines. Once the grind is established, you refine it with finer belts and/or hand sanding until it is at the desired thickness for HT. That is usually .020-.030" for carbon steels, and .010-.020" for stainless steels. After HT you re-sand the edge to remove decarb, and take it to its final surface smoothness/finish. This should leave the edge thinner. Normally at the time of sharpening, the edge 1s between .005 and .010".
 
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