Plunge Line?

[DANA HOLMAN]

Hey Guys, I have a question about plunge lines. At the top of the plunge line there is usually a small curve, how do you get both sides the same and not end up grinding to the top? I've been trying to figure this for 4 1/2 yr.     I can get one side to look pretty good but can't get the other side to match. I'm sure its just practice, but if there are any tricks, I like to know.


Thanks Dana

[D.Ellis]

Belt tracking needs to be even on both sides.....same amount of overlap off the edge of the platen or contact wheel. Other than that, it's just practice getting the pressure and angles the same on both sides. Some of the pro's may have more tricks that I don't know about.
Darcy  

[tomsm44]

Maybe do a single bevel blade?     :D   just kidding.  I've been trying to figure that same thing out.  The only way I can even get close is to use fine grot and low speed at the end and be really patient.  I still can't manage to get it just right though.  Hope you get some good tips on this as I need them too.

Matt Toms

[kbaknife]

I am not - I swear - not being a smart a**.
You just stop before you get there.
I'm reminded of the guy who goes to the Doctor and raises his arm over his head and says, "Doctor - it hurts when I do this!".
The Doctor says, "Then don't do that."
And I will say this - no doubt, the single most important shop improvement I made early on was getting a variable speed grinder. This made it possible to slow down and minimize mistakes.
Even though I will admit that mistakes are great teachers.
Grind edge up.
Tip the EDGE into the platen and not the spine.
Do things in stages.
Small steps.
You should be able to see this problem coming your way before it gets there.
Then just slow down and avoid it.
I don't know what your grinding set-up is - what grinder, platen, motor control, etc.
Those have a lot to do with your ability to control your actions.
Knife making isn't easy or cheap, if you want to make the best knife you are able to make.
In the words of my mentor, Jerry Rados, "Knife making is a life time of buying tools, and then you die."
The variable speed grinder made all things possible for me.
Then it was up to me to practice.
I ended my first 2-3 years of knife making with BUCKETS of failed blades.
Buckets.
I doesn't come easy.
Those successful are the ones who don't give up.
It's easy to see you will be one of the successful ones.


 

Originally posted by DANA HOLMAN:
 ....how do you get both sides the same and not end up grinding to the top?
Thanks Dana

[Doug Campbell]

I'll only add a couple things, first I always cut both plunges on the same side of the belt. Meaning I turn the belt around to do the second side. Belt edges tend to get worn differently...

Second, one of the best pieces of advice I ever got was from Bruce Bump, "use sandpaper like it's free". Sharp belts or sandpaper can make all the difference.

[DANA HOLMAN]

Thanks Guys, Karl my set up is still the same, 42" craftmans, no variable speed, but one day i will have the right tools. Ive have been grinding with the edge down for a long time, but im trying to change my bad habit.
Thanks again Dana

[srtben]

Originally posted by kbaknife:
.... "Knife making is a life time of buying tools, and then you die."..

Thats a perfect quote Karl!


A carbide file guide can really help, as it allows you to grind right up against it on both sides.
I have one and use it occasionally for that.

I know it has been said, I had a hard time believing it too, but PRACTICE really is the key. And sometimes you are just gonna screw up, I do all the time.

Like Karl said, slowly sneak up on it. Don't try and cut in your plunge the first time you put steel to belt.

[kbaknife]

All of this advice is really good!
Doug's is something a lot of folks never consider - both sides of the belt are not identical. They will result in a slightly different radius in how they grind.
And I, too, have recently started using my file guide on my initial cuts. I get everything pretty close, in the right zone, and then remove the guide so I can see to get things just how I like them.
I would never even consider grinding a blade edge down. I know some can do it, but I'm not that good.
I have to be able to see the cutting edge to be able to keep it in the center.

[Doug Campbell]

Wow Dana, never realized you were grinding edge down. I'm like Karl and sure not good enough to pull that one off. I think when you get the hang of edge up it will make your life much easier.

I also use one of Uncle Al's file guides. I pretty much completely grind my blade at 50 gr but hold forward just a little from where I want the plunge to finish. I then switch to 120, clamp on the guide and complete the plunges. That little file guide is a wonderful tool.

[kbaknife]

Good point Doug!
Don't start where you want to end up.
Get some of the major material out of the way, staying in front of the final end-point, and then slowly creep back, gradually evening things up as you go.
Can't put it back on once you grind it off!

[Track]

I thought I was the only one with this problem. A lot of great advise here. I'll be saving for a variable speed grinder and switching belts around.

[DANA HOLMAN]

Doug, Karl, yea I been doing it that way for a long time, you just look at your blades edge a lot, but that's just me (Bad Habit). I have used a file guide to cut the plunge lines before, but not all the  time. after thing about how I do my grinding I think my big problem is I leave the leather on my platen when grinding. I don't have a changeable platen. Maybe I'll make one. Thanks for the good advise from all of your guys. I should be posting a few in a week or so. Karl I finial made another dagger #2 it a little different so we'll se what you think.
Thanks again  Dana

[tomsm44]

Edge down may make it a little harder to keep your plunge lines from going out of the top of the blade.  My experience so far has been that the belt wants to grab at the top of whatever you are grinding and take off more metal there.  Edge up naturally removes more at the edge and I have to apply extra pressure at the spine to move my plunge line up.  Seems that edge down would want to take metal away toward the spine with less pressure.  Not sure I'm right but that's just my two pesos.  Thanks guys for all of the advice I can now poach for my own use.    

[madness522]

One other thing that makes a difference in the way both little curve at the top looks is having your platten edges the same on both sides.
 I had that problem when I firt started.  I built a NWG and rounded one edge more than the other and had all kinds of trouble getting them to match. Also having the platten parallel to your belt will help.  Does that make sense?  What I mean is if you run the tracking off so you can see the platten edge with the belt turning is the distance the same all the way up both sides.

[tippit]

Great words of wisdom here.  I know Burt Foster does his final rolled edge down...but I have a hard time figuring out where I am doing that.  Save those buckets of throw aways and use them for practice by grinding a different plunge line the next time.

[DANA HOLMAN]

Thanks Guys for all the info and help.
Dana

[Steve Nuckels]

Good thread!  Very helpful!

Steve
-----------
Potomac Forge
Member, W.F. Moran Jr. Museum & Foundation

[Lamey]

not sure if its been mentioned, but also put a radius on your platen edges.  This along with rolling the edge of the belt over the platen slightly helps get that nice curve at the top of the plunge.

[DANA HOLMAN]

Thanks Lamey, I'll give it a try.
Dana

[Arock]

You can get a file guide from USA knife maker it's hardened you have to use a file and it will be even on both sides