What is the ideal size of wheel for hollow grinding?

G

Grizzly Bear

Well-Known Member
I just bought a new grinder with a 14 inch wheel on it to do hollow grinding. I am running into trouble because I can't see the hollow grind in the blade. The wheel is so large it doesn't seem to make a scoop in the blade. What size wheel do you guys suggest using to get good hollow grinds? Should I spend the money on a serrated wheel?

Thanks for your help.

Grizzly Bear

PS. I am having good luck grinding concave blades. I like the looks of them better than flat grinds. I however think the hollow ground is the prettiest and would like to get the proper size wheel to make them.
 
Not saying my procedure or tools are the best or correct methods, but I made a homemade 8-1/4" hollow grind wheel that seems to work ok for me. I have heard of 10" or 12" and do recall someone here mentioning a 20" wow that's big!


Wayne
 
A lot of it has to do with personal preference, but what also need to be considered is the type of edge you will end up with, based on the size of wheel you choose. All too often what many call a "hollow" grind is really a perversion of a hollow grind. A true hollow grind is one where the "hollow" starts at the spine of a blade, and terminates at the edge, with very minimal edge bevels. The most common examples are well made straight razors.

What most do these days in terms of a "hollow" grind stems from what a production knife company came up with a few decades ago..... a hollow that does not extend to the spine of the blade (sometimes only 1/2-3/4 of the blade is hollow ground), and leaves the edge overly thick, necessitating very large/obtuse edge bevels. This was first done to compensate for steel that was too hard, in an attempt to prevent edges from chipping, and/or blades from breaking. For some reason it caught on, and in many circles it's now considered the "norm" for hollow grinds. It's easy to spot....when you look at an knife with this type of grind, the edge bevels are generally way oversized, and very obtuse. Personally I've never understood why anyone would want to build that kind of cutting resistance into a blade. But as with others things, many do it simply because someone else told them "Its the best".

OK, all that being said, while a true hollow grind does have a place in the knife world, I choose to only use it on those type blades where it's a benefit rather then a hindrance. I've seen hollow grinds done with everything from a 3" wheel, all the way up to 18-20" wheels. The smaller the wheel, obviously the smaller the "hollow". The most common size wheel I have seen over the years is a 10". Personally, when I do produce a blade with a hollow grind, I will most often use a 10" wheel, but because I demand that the grind be "right", and not one of those aforementioned perversions, the size wheel is determined by the thickness and width (edge to spine) of the blade.
 
I know a lot of friends use the 14. I have an 18 on my grinder which is house made. Now one are going the 20 inch route. My main interest was a grind from back of blade to the edge with no stop to the grind.
 
Although I have other size wheels, I pretty much settled on 10" for most everything I grind. That's a personal preference and works for me. There's no reason to not get a fine edge with proper blending...which will take practice and a mental plan depending on stock thickness and the look you want. A straight back and forth hollow is pretty uneventful so by 'pushing' your grind you can add some character to the blade. That's where the blending comes in...too deep and you blow through the blade or take off the edge. There's some contortions involved but you'll figure that out once you're not getting the look you want. Starting out I'd stick to a smooth wheel but if you want to get there quick on thick stock, use a serrated and finish with the smooth on slower speeds.


Rudy
 
I started out with only flat grinds and only recently started hollow grinding. I'm still not perfect at it, but I'm using a 10" wheel and want a bigger one. I keep feeling like I'm limited by the 10" and I'm not good enough yet to try blending it up. The 14" wheel would be great IMO, or even bigger. I like the look of a shallow, full height hollow. I'd say just go with it and maybe it'll grow on you.
 
! like the 10" when hollow grinding but flat grind as well. I believe Ed has given a good explanation of what the result should be. A serrated wheel is not one I would pick for finishing work.
Frank
 
Thanks a lot knife dogs. I guess I will stay with the 14 inch and learn to use it properly. After reading Ed's comment I now understand that I am probably trying to get an exaggerated hollow grind. Hollow grinding is new to me and I need a lot of practice!

Grizzly Bear
 
A serrated wheel is not one I would pick for finishing work.
Click to expand...
I totally agree with Frank.

I didn't think to give you an explanation of Smooth versus Serrated wheels. Generally you can expect serrated wheels to remove material more rapidly, but leave a harsher finish. Smooth wheels remove material at a lesser rate, but leave a much finer finish then a serrated wheel with the same belt/grit.
 
I did my first hollow grinds on a regular bench grinder with a 8" stone wheel. I didn't know what I was missing until I got my first belt grinder.
 
I am using a 10in serrated and a 10 smooth, I want to get a 12 or 14 but you know how it goes. A never ending list of tools to add to the arsenal :D The serrated with a 50 grit blaze makes quick work of getting your grind started.... that or messing up without waisting any time :D of course that is how we get new designs right? :p
 
I have been getting nice finishes on larger knives with a serrated 14" wheel using 3x132 cork belts, green then white compound. The stiffness of the cork belt allows for the finish work. I like the large wheels because you can get a "taller" grind with minimal undercutting. I started with a 10" 2x72 setup though.
 
I personally love hollow ground blades for everything except camp chores. I make mostly bowies but also grind slip joints and hunting knives on a 24" wheel. It mostly looks flat on a small blade but it is hollow. All the old English bowies were hollow ground on huge stones.
 
You must log in or register to reply here.
Back
Top