Feedback on my 1st hollow grind

[shamu]

I just tried my first hollow grind on a 10" wheel. For some reason the process was more enjoyable that flat grinding on the platen. 1095 nj steel. grit progression 40, 60, 120, 220, 400, 600.

My initial thoughts:

- The initial plunge line cut gave me trouble on one side.
- My left side (weak side) wasn't nearly as awful as it was w/flat grinding.
- My bevels are uneven, but it seemed nearly impossible to correct.

Questions:

- would you even bother sending this off for HT?
- Does the flared out part of the edge go too far up the bevel at the point where the edge begins to curve up to the point?
- Does anyone have any good tutorials on creating the edge? That would be post-HT right?

Thank you...

 

[Justin Schmidt]

check out ekim knives on youtube. he does a very good in depth tutorial. so does walter sorrells, i believe walter talks about this. I'm no expert but from what I've read that low dip in the middle of your bevel is caused from uneven pressure while grinding. basically midway through your grind you adjust or let up and it causes that dip. but don't take my word for it I'd wait for a more experienced person to chime in.

 

[shamu]

Thanks Valknut

 

[Lo/Rez]

I can't remember who said it...finish every knife you make because you will learn something from each one.

 

[Justin Schmidt]

https://youtu.be/FnvGlUGLVGU

about the 22 min mark is where he talks about walking the bevel up in the middle. I'll see if I can find the video that gets more in depth about it.

 

[Justin Schmidt]

aha! I found it!
https://youtu.be/1C0spGxmggE

9:45 is about where he starts talking about it and how to fix it. hope this helps

 

[Justice4all]

While I don't really do hollow grinds anymore, it was kind of fun in that I did it freehand vs. using a tool rest like I use for flat grinding.

First, 40 grit seems a bit aggressive to me. Getting all those deep grind marks out, especially the minor mistakes would be a lot of work. Personally I'd start with 60 or 80, but that's me. It also allows for a bit lighter cutting while establishing the initial bevel. Once the initial is established, things get a bunch easier as you can "ride" the blade into the wheel and simply hold it there until you apply pressure to start the cutting. I apply pressure with the fingers of my offhand which allows for more precision.

The groves you have on both the plunge portion of the bevel and the midway point are from the edges of the belt. The edges of the belt cut very fast and will change the height of your bevel in an instant. You really want to work on keeping the blade flat against the wheel and the pressure equal for the entire stroke - at least for now. The smiley face shaped bevel is from hitting the edges like I've said, but also from not having a smooth left to right or right to left stroke as you are going across the belt.

I'd practice a bit first before sending anything off to HT. My first hollow grind burned right through the blade, my second and third came out well enough to finish the blades.

Yes, the bevel goes up too far towards the edge of the blade and into the spine. My opinion is to work on a good even "pull" across the belt, keeping the blade flat against the cutting surface before trying to get the bevels to do anything more fancy.

When you say "creating the edge", do you mean the cutting edge bevel? If so, yes, that is post HT. I have my own unique way of doing it, which I'll be doing a vid here of shortly. I essentially use a Norton Norax X100 engineered AO for going from no edge to razor sharp in just a few minutes. It's quite different from what others do but it makes a very good edge. There are some simple vids on my FB page that show how sharp the edges get and how well they hold up.

I'm not sure I'd worry about this quite yet though. Once you can get a moderately straight primary bevel, you can work on fine tuning edge thickness and then creating the cutting or edge bevel as it requires the same set of movements.

 

[shamu]

Thank you justice

 

[john april]

one side of the plunge is higher because you angled the knife and it was only touching the edge of the belt. keep it flat on the face of the wheel and that wont happen.

 

[shamu]

thanks woodster.

 

[Craig Daniel]

You do not have to make a pass all the way from ricasso to tip in one pass. You can get your hollow established at the first 2-3 inches and work there to the tip to finish the grind. Do you mark a center or a stop at say 25 or 30 thousandths pre heat treat? I saw your edge was a little off was the reason for the center markers, Don't get discouraged about the uneven grind. Every maker if they are honest will tell you they also did the same thing starting out, Experience is your friend being from some hands on. Is there any makers who is willing to help you who are near? How far are you from Beckley WV?