Plunge lines

Thanks for the input, guys!

AcridSaint,

I assume you mean a more acute(?) radius in the plunge as opposed to the gradual slope? If so, any advice other than you just have to do it?

My first experience on the grinder was with a piece of scrap and I used double scribe lines. I was having trouble 'feeling it', so I tried the single this time and I think I might like it better but will keep experimenting...
 
I guess it depends on your equipment and how you're grinding. Are you rolling the belt over the edge of your platen/wheel? How thick the belt is can also change the angle/radius of the plunge.

You should have a plunge that the radius/angle of your tool fits into - so if you used a 3/16" round file to put the plunge in, everything should be flat, except right against the plunge where the radius of the file starts. If you fold your belt over, the same thing applies. So, if you lay that blade flat on the platen (or set into the hollow on the wheel) and imagine lines coming straight off the platen/wheel in either direction, your tip and tang should be parallel with those lines. Where the plunge changes angle, the tool should also fit.

In order to fix a plunge that wedges like that, I would come in flat and then put more pressure on the handle side and pull it across the belt lightly. Kind of hard to explain without holding the knife, but the idea with changing any part of the grind is to tilt/twist/turn subtly until the steel does what you want.

That's my take on it, not the only way, maybe not the right way - just how it works for me. Hope that helps some.
 
Yes, I think I understand in principle. I'm just freehanding on the grinder, not using any guides or doing any filing ahead of time. I'm limited right now as the platen on my Craftsman is much wider than the belt, so I can't run it off the edge. I do have a ceramic liner on the way, so hopefully that will make things easier.
 
You should have enough tracking adjustment to track it off one side (or both). Without being able to get the belt at the edge or folded over the edge, I think you'll always struggle with plunges, even if you file them in beforehand. I started on a 4x36, so I know all too well about limitations of a sander. Play with the belts and see if you can get them tracked off of one side (preferably both). If you can get it over one edge, you can at least clean up with it. Once the ceramic liner is on there, it will help tremendously if it helps you get the edge of the belt over both sides.

Don't worry about using jigs, I learned without them and I'm glad for it. You can get stuck in one routine if you learn on them. I think their place is for folks that have a set purpose in using them.
 
Sorry again Big Smitty for the hijack...

Tinkered a bit more during lunch. Better I think but still not perfect. This time I used a good quality 120 grit. The platen must be 3"+ wide not allowing me to run the belt off the edge, so I'm hoping this will be much easier once the 2" liner is on.

IMG_1034.jpg


IMG_1035.jpg
 
I think they're looking better, keep it up! Since you probably don't want to grind down the spine any more, you can put your blade flat against the platen and then start twisting in toward the platen slightly, that will allow you to change your grind angle and thin out the edge without taking much more off the top. Take it slow, just think about twisting your wrist, you have plenty of material and time to work out how to do it, so don't worry or rush.

Sorry about the hijack as well, hopefully this will prove useful to folks wondering about plunges.
 
PJ234, It looks to me like your belt is either to fine grit or dull and needs to be changed . use a fresh 60 grit belt and grind edge up .Lock your wrists to your sides and move side to side with your hips. Start at the plunge area and grind to the tip in a smooth fluid motion pull the blade off of the belt, look at your grind , make the necessary corrections and repeat,grind in one direction only(or at least untill you can produce a clean grind this way) . Make sure you don't appily to much pressure on the plunge area, keep your blade at an approx 8-10 degree angle. One hand is your guide and the other hand maintains your angle. Looking at your blades shows me that you are trying to get a full grind befor you are grinding to your center scribe line. Keep a loose but firm grip on your knife handle and maintain your angle, looks like your angle hand is getting lazy. Once you have established a good grind bevel you should be able to feel it . Stay with that angle. Just like everything worth learning ,it takes patience and practice. You can do it , I know it is frustrating at times however you will learn . Study each blade you grind , it will tell you what you are doing right or wrong . Learn to read your grind and take the necessary steps to correct the mistakes made on the previous grind.Don't get frustrated and use crutches ,you will only limit your own abilities and waste time.In the long run you will be a much better grinder by learning the right way in the beginning.
 
Oh , Keep your belt tracking in check adjust as necessary.Looks like your belt is overhanging on one side more than the other.
 
PJ

Don't worry about highjacking the thread. Your input is on topic and i am still learning. I have the same Sears grinder you have and adding a ceramic platen makes a huge difference. I just went to Home Depot and had them cut me a tile to size and JB welded it to the existing platen. I then used an angle grinder with a cut off wheel to remove the excess platen metal below the bottom bracket that holds the platen on the grinder. This mod allows tight grinding when you are profiling the shape of the knife in tight spots. From the looks of the knives you posted, we are at about the same skill level. Good luck.
 
Just a quick note... I ground my fourth and fifth blades today.. no crutches required. I was a little hesitant to freehand after taking so long for my low skills and underpowered equipment to get the blades shaped, but I went with it and they turned out pretty well (all things considered). They're far from perfect, but I feel I'm getting better. Just wanted to give a "Thanks!" to the posters in this thread... especially Trace Rinaldi and Ken Onion... you helped me get my head in the right spot!
-Mark
 
You must log in or register to reply here.
Back
Top