what are some ways to get a hollow ground blade?

[boysurvivalist]

my knives usualy end up not very good cutters because i cant seem to get a false edge or a sharp edge at all any one help me

 

[Matt Shade]

For a hollow ground edge you need to be using a grinder that has a round grinding surface. It can be a bench grinder, a burr king with contact wheels, etc. The size of the wheel depends on how hollow ground you want the edge to be. The larger the wheel the flatter the grind is. For larger knive I would want at least an 8 inch wheel so that the edge isn't so thin that it breaks easily.A good work rest is important to, without it you'll have trouble getting even grinds.
If your having trouble getting things sharp there are several things that could be wrong.Sharpening is a funny thing becasue different steels have to be worked with differently, and differnt materials cut better with different edges. The blade needs to be heat treated to just the right hardness. To hard and it will be brittle, to soft and it won't hold an edge. To start you need to know what type of steel your working with, and the best way to sharpen it, as some steels will roll the edge easier and things like that.Having the right angle is important. The angle should be between 15 and 30 degrees. The thinner the edge (15 degree angle) the sharper the it will be and the better it will cut. But thin edges roll and chip more easily. So if the knife is going to be used for hard cutting or abusive use, you want a thicker edge(30 degree angle.
If your hollow grinds won't get sharp they might be to thick at the edge. If your using a small diameter grinding wheel for high hollow grinds you may be getting the blade thin in the middle and leaving it thick at the edge. Try making the grinds a little closer to the cutting edge and not so high up the blade. Then using a coarse stone or diamond file put the secondary bevel(cutting edge)on at the right angle to the rest of the blade.Hope this helps.

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Fix it right the first time, use Baling Wire !

 

[Jim Smyth]

To answer the first question, you obtain the hollow grind buy making sure the blade is of an even thickness. I use a digital mic for this and try to get it to within a few thousandths. Then when it's sanded down to the grit you like I use Dykem which is a blue die to cover the bottom of the blade. You want to scribe a line down the middle of the blade where you want to put the edge on. You can do 1 line in the middle or do 2 lines on each side but you need to get to about .025 to .030 thickness on the edge when your done grinding. They sell these scribers at most of the knife makers supply houses. Kovel/Sheffields etc.

Then comes the tricky part, at least for me. You need to grind the same amount of material off both sides. I take 2 passes on my Wilton square wheel grinder from the tip to the ricasso. Then I start from the ricasso and work back to the tip and I keep that motion taking a little more off each time. Once you get the center section down to your .025/.030 thickness you can tilt the blade to move the hollow grind up to the top of the blade slowly taking a little more off each pass. When you happy with the way 1 side looks, switch and do the other side to match. This takes alot of practice to do right and I am by no means an expert. I would suggest using scrap metal for a while till you get the hang of it. I have made about 20 folders so far and the hollow grinding has been my biggest challenge. If you ever get the chance to see it done in person it will be well worth it.

As far as putting an edge on it you will need to experiment with different grits and angles to acheive the goals you want. Some like a coarser edge for a sort of serrated feel to cutting things. Some like a smooth, like a razor edge that can shave hair off your arms. Guess it depends on your preference and what you intend to do with the knives when there done.

 

[Dr.Lathe]

Hollow grinding is my favorite style and would be glad to help you with it if I can. If you are just starting out, it is much easier to start with flat grinding. I started making flat ground knives on a grinder made out of a 2HP motor, reversing switch and a 9" face plate. This grinder cost less than $100 and turned out some nice knives, if I say so myself

I still use it for shaping Kydex and other things.
If you would like to build a grinder like the one I mentioned above, Email me! I can tell you where to get the parts to make one.
Neil

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