First Stock Removal

Eric Poris

Gold Membership
Sup Dogs,

So I just got my grinder up and running last night. Naturally, I was up until the wee hours of the morning practicing on it with wood paint sticks. I then decided hell with it, and grabbed a piece of CPM154 then started grinding it. This is the result.

I have read a bunch of books and watched a ton of videos before this and I have to say I learned more just by doing it than anything else. I think I made the blade a little too wide in the hallow. There are parts of the grind the 8" wheel won't touch in a single pass. Still trying to correct this. I also think I needed to bring the tip closer to the front of the blade and I should have started the drop point closer, towards the handle.

Have a few questions. There are still some pits in the blade I tried to grind out but no matter how long I grind it on the flat platen it seems like they never get any smaller. Anyone have any tips on this? Also, how do you determine how thick the hallow grind should be? Like I said, I think I made the hallow a little too thick and may have started to hallow out the blade.

All comments are welcome and thanks for looking!

Woof,
Eric
 
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Eric Ochs

Well-Known Member
Eric,
You look to have a good start there. As far as the 'pits' you are referring to I assume these are from the bark of the descalded steel...Keep going they will come out. Also, consider purchasing your metal percision ground or get it ground yourself. Which is what I do. If you choose not to do that, and starting out it might not really be worth it anyway, but try some differert approaches. Personally I would suggest you get the bark off of the blade BEFORE grinding any primary bevels.

Regarding your hollow grind question I would suggest you get a large piece of paper and a compass and draw yourself a bunch of circles in wheel sizes(4", 6", 8",10"...) . Then make a similar diagram for yourself to represent some different sizes of bar steel in cross section preferable with a somewhat opaque paper, then hold the cross section steel bar cut outs up to the wheel circles....and check out how it looks. Once you have an understanding of that...

check out the gizmo Gordan posted it is kind of cool.

http://bimjo.com/free/widget.html Try this it has helped me alot.
Gordon

Most of all Eric, I think you actually hit the nail on the head, you will learn more just by doing than anything. I built my first knife out of mild steel and never heat treated it and really it is worthless except I learned to grind doing it....There is nothing wrong with using some cheap stuff to see if you can make the grinds work before burning $20 worth of steel. I have also found that in starting complicated new grinds now I start out with two or more blades...once I work out the tough transitions on the first one the second one seems to flow better.

Hope that helps,
Eric
 

Dustin Turpin

Well-Known Member
Eric had a lot of great advice. There are many variables to consider before starting the knife and they govern what size material to purchase and start with. 10 different makers will probably do some things 10 different ways. It is what works best for you that matters.

Main thing to consider when hollow grinding is the size of your contact wheel. Your grinds will always vary depending on the wheel size. Smaller wheels give you a shorter grind specially in thinner stock. Larger wheels will develop a taller grind much quicker as you reach your desired edge thickness. Of course you can change the angle of the hold to produce any height you want, but it becomes more difficult to keep your grinds consistent. It is best to always keep your grind within the radius of the wheel. That way the wheel is always making full contact to the work piece and giving you a very nice consistent pattern.

You almost always want to get your material completely surfaced before you start a grind. You don't need to take it to finish, but you want to make sure any visible blemishes like pits and waves are gone. I usually take my stock up to 120 before I start a grind. I will start my grinds with a 60 grit and once I got a nice bevel developed I will move onto the swedge or false edge before I finish my flats. Once I got the flats finished using a platen I will than return to my main grind and finish it up. This is a sequence I am comfortable with, but may not work for everyone. I do find it best to have my flats completely finished before I finish the hollow grind. Sometimes you may need to redo flats after the hollow grind. Just want to maker sure not to take any definition away from the grind lines. It all falls into place with practice like anything else. Don't be worried if you have to take a few steps back to clean up a piece. It happens to all of us.

Like Eric said I would try to stick with precision ground stock until you get a surface grinder or can out source the surface grinding. It will save you a ton of time and headaches down the road. It will also mainly save on belts. I don't even want to think of all the belts I have gone through in the past surface grinding my own stock with just my platen.

One last thing.. make sure you get a very clean 45 degree edge before you start a grind. It is the heart of getting a clean straight blade. Practice doing your 45's before you really get into hollow grinding. You can do it with a platen or a wheel. I personally like using my 10" wheel and a work rest.
 

Eric Poris

Gold Membership
Hey guys,
Thanks for all the great information and suggestions, I really took them to heart. I think it really helped out. Here are a few shots of a more recent attempt of the same design...please forgive the awful photography ;)

View attachment 16940View attachment 16941View attachment 16942View attachment 16943View attachment 16944

A lot better on my second run I think. I found that grind height widget to really help.
Dustin, you are right about the 45s. I figured it would be pretty easy to grind some clean 45s, but no. Turns out, I spent a good amount of time on them because it wasn't easy at all but I think it really helped.
Again, all comments are welcome and thanks for looking!
-Eric
 
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