Hints for plunge lines

6

629hugo

Joined
Feb 10, 2013
Messages
191
How do you guys grind in your plunge lines. I am new at this, maybe done about 10 knives and each on I spend most time trying to fix my imperfect plunge lines. The current knife I am working on now is about to go into the garbage. Can yall share some secrets?

H
 
I have been using a file guide, I know I need more practice at grinding with a steady hand, but the current knife I couldnt get a smooth taper into the plunge. The plunge was almost parallel to the edge of the file guide. Then I ground off so much blade to try and fix that it is changing the original blade shape!!!!! AHHHHHHHHHHHHH!!
 
I am am about 350 knives into my career.

I still fight with plunges.

A good file guide helps, although I do not use one for them any more.

This is my advice for every step in knife making, keep at it.

These are hard won skills. Knife making is HARD work. Don't give up.

If you grind bad plunges, throw it away and grind another, if that one is not right throw it away.

Believe it or not all that throwing away of your hard work forces you to do a better job on the next one.

It also gets you valuable practice and helps with muscle memory.

At ten knives my work looked terrible. That's just the price we all pay.

Keep trying.

Greg
 
I am working on a dagger, and i used files rather than the grinder to do the plunges. A variable speed grinder helps, but its mostly experience. I'm struggling with plunges too.
 
Plunges are one of the very first things serious buyers look at closely. There's a good reason for that - nice plunges demonstrate skill and attention to detail. Like the others, I still struggle with them.

Greg is right, there's no substitute for practice. If I were to design a class on grinding blades, there would be one full day devoted to nothing but grinding even, symmetrical plunges over and over again. Take a bar of mild steel and just start from one end, grinding plunges.

Many, if not most makers radius the edge of their platen to help them with plunge lines. Trying to grind a round plunge on a square-edged platen is folly.

Round files and a file guide definitely help clean up an imperfect plunge (they are also nearly indispensable for properly relieving/squaring up the shoulders of a hidden tang blade). You can also just set your plunge with the file/guide and then grind your bevel up to it.

One major "Why didn't I think of that?" tip I learned here for evening out plunges and smoothing out deep file scratches in tight spots is to use Cratex "bits" in a rotary tool. They can be shaped/contoured to your needs by running them against a sharp file.
 
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I'm new also, and just learned a valuable lesson on doing plunge lines. I did a shop visit with a very experienced maker, and he showed me that after you scribe your center line on the blade edge, also scribe a perpendicular line where you want your plunge line to be. Then when you have the knife on the grinder you actually have a fixed line to grind to. I would always put one plunge line where I wanted it on one side, and then try to match it on the other side. My problem was that I could never match it. I don't know if this will work for you, but it did for me.
 
Get a carbide file guide from uncle Al @ Riverside machine, this will help you whether you grind on a machine or draw file. Next, get some mild steel flat stock and practice making plunge cuts over and over down the length of the bar. This should help you develop some skill. Layout is everything! Be patient, take your time.
Practice, practice, practice!
If you are forging your blades then make a fuller to set your plunge lines in the right ballpark, then you can refine them later grinding or filing. I made mine from 3/8" mild plate. I welded two 1/4" bars to the bottom plate, one on each side at right angles on one end. I drilled a series of holes up the two flat bars so I could set differnt angles, the second piece of 3/8" plate gets one hole drilled thru it and slips between the two flat bars with a bolt thru it. now you have two surfaces in the same plane. You can use this tool to set shoulders and draw out your tang as well. weld your hardy shank to the bottom piece that doesn't move.
Hope these ideas help...
 
PRACTICE!!! --- As everyone has stated this grinding blades does'nt come
over nite.
Ken.
 
You don't say at what grit belt you start your grinding...I'm guessing a 36 or 60 for rough grinding. Stay away from where you want your plunges to be with the heavier grits. Wait until you get to 220 before you start trying to get them to match. A big dead flat piece of steel with a nice radius on an edge will let you fine tune the plunges with a piece of paper glued to it. You can have different radii on the edges for the different sizes knives or plunge lines.
 
I grind my plunges in before heat treat about 1/16 short of where I want them to end up. Then when I'm done with the HT, I take a sharp 120 belt and the file guide and move the plunge back to where it belongs. File guide, sharp belts, slow speed, hardened steel are all helpful. Like the other guys, I'm 277 knives into this thing and still struggle with the plunges. Hard to learn, hard to keep right. I've seen MS knives with crooked plunges, from guys who obviously know how to do them right. Seems like something you have to pay real attention to on ever knife.
 
They are tough. I am getting better but I still can't get an actual plunge. Mine are more of a steep hill.
 
Jason Fry said:
I grind my plunges in before heat treat about 1/16 short of where I want them to end up. Then when I'm done with the HT, I take a sharp 120 belt and the file guide and move the plunge back to where it belongs. File guide, sharp belts, slow speed, hardened steel are all helpful. Like the other guys, I'm 277 knives into this thing and still struggle with the plunges. Hard to learn, hard to keep right. I've seen MS knives with crooked plunges, from guys who obviously know how to do them right. Seems like something you have to pay real attention to on ever knife.
Click to expand...

+1 Totally agree
 
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