perfect plunges

J

jkf96a

Well-Known Member
At the show I just did, I had 5 different guild members and 3 mastersmiths give me a good solid knife critique at my request. EVERY SINGLE ONE pointed out that my plunges were not consistently even. A couple also pointed out that the top of the plunge where the bevel meets the flat was also uneven on some of my blades.

Help! Other than just paying more attention to those things, what suggestions do you guys have for getting even plunges?

Overall my knives got good reviews, but this was definitely a sticking point.
 
This has been my major problem! I can't figure it out...

The way I have been able to get them remotely close is by cutting them in with a round file and file guide. Then I still have the problem at the top of the plunge.
 
I believe what is known as a file guide will correct that problem. They are for sale but you can make one yourself with some care. The two cross bars do require hardening, and the holes for the bolts on each end must be drilled for the sholders of the bolts not the threads. I don't do pictures. Sorry about that, however I'm sure someone will pop in with a picture or two. Frank
 
Bruce Bump has some mighty fine File guides, and his have carbide faced so they can be used on a belt grinder. Making one from O1 or similar works fine, I really enjoy being able to use the grinder to cut nice crisp and even shoulders!

Good Luck and God Bless
Mike
 
Diamond G Knives said:
Bruce Bump has some mighty fine File guides, and his have carbide faced so they can be used on a belt grinder. Making one from O1 or similar works fine, I really enjoy being able to use the grinder to cut nice crisp and even shoulders!

Good Luck and God Bless
Mike
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Mike, you're right. Those BB File guides are awesome. I bought one a few weeks ago and its the best 120 I've spent in a while.

Jason, I've had to make sure that my platen has even sides and that there is nothing to interfere with guide when cutting my plunge lines. Be careful when you move up to the finer grits, I've had issues with them cutting "funky" shoulders when not watched.
 
I own and use two of Bruce Bumps file guides and I do recommend that you purchase one, I also recommed that you slow down and concentrate on making the plunge lines even by slowing down the machine with a sharp new belt and make even and constant passes until you have nice even plunge lines.

You can do it! Even try going to a finer grit belt and make your passes until they line up on the bottom and the top! Even with using a B.B. file guide, I still do the final 600 grit and then Cork belt passes without it.

Laurence

www.rhinoknives.com
 
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Here is a grinding guide, that comes with a sight reference that will help you produce not only even plunges but matching bevels as well. You can see it in operation if you care to bubblejig.com
It can be used to sharpen blades, grind false edges and surface grind guards and butt caps to 4 place accuracy as well.


This is a proven product that is guaranteed by the maker, we have shipped 700 of these handy tools, worldwide, since Jan 2010.

DSC00866.JPG


Bruce does make a fine file guide.

Fred
 
Also practice with a few "scrap" blades and get use to running the belt off of the platen just a bit, this will give you a different radius depending on how far off you let the belt track.
As Laurence said, practice, practice, practice. It is easy to get discouraged, don't be, count them as learning tools and keep going.

One tip I got many years ago was to finish EVERY knife I started, if it's beyond what I am willing to accept for quality (uneven grind, bad grind lines, shoulders off, ect) you are now not afraid of messing it up! Use it to refine your technique!

Good luck and keep at it!

God Bless
Mike
 
I still use a file guide for plunges and I've ground blades for 20 years. Fred's bubble jig works great, my apprentice Bill Dirk had one here and made some amazing mirror image grinds with it. I suggest simply clamping steel plates on both sides of the blade and see how easy the plunges become. I've made several file guides that work but wear out quickly. The carbide inserts take care of that problem.
 
I did what Bruce is referring to for years. Get a 1" C-clamp and two pieces of scrap stock steel of say 1/8" thick. Clamp the two pieces down tightly where you want your plunges and start grinding. It will wear out after a few knives, just get two more even pieces or re-true the existing ones.

Laurence

www.rhinoknives.com
 
Jason,
i have the same problem actually specially that my platen is not even on both sides

now great makers already addressed the file guide part to i will give you my experience on other things, as mentioned platen even, if you're using a wheel you avoid that part, 2 when grinding the plunge make sure the belt extends exactly the same length outside the platen or wheel on both sides (not sure of i explained that the right way), use fresh belt as Laurence said, concentrate and let the belt do the work, some makers (or all?) break the edges of the belts with a piece of steel, i never tried that but i believe it could help. finally if you hand sand, dont take too much from the plunge area to remove those $%@%@# scratches hiding in there without doing even passes on the rest of the bevel, i did that before and the plunge area ended up looking funny

more experienced makers will probably give you even better info :)

hope that helps!
 
rhinoknives said:
I did what Bruce is referring to for years. Get a 1" C-clamp and two pieces of scrap stock steel of say 1/8" thick. Clamp the two pieces down tightly where you want your plunges and start grinding. It will wear out after a few knives, just get two more even pieces or re-true the existing ones.
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i just might try that!
thanks for sharing Laurence :)
 
If my too-many-knives-left-after-the-show clearance sale keeps going like it has been, I'll hit you up for a file guide, Bruce. Sold 2 of 21 at the show, but sold two more Monday and two already today.
 
The Bubble Jig can be used in combination with Bruce's file guide; it works great.
Barryssteel003.jpg


I have not had the pleasure of using one of Bruce's file guides, but I know they are made to perfection as his knives are.
 
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I was thinking of getting one of these file guides someday, mainly cause my eyesight is getting bad in my old age. With that being said, it is possible to free hand your grinds and get your termination lines and your shoulders as even as you could possibly want! It takes at least one hundred blades under your belt to get good at free hand grinding, Its what they call paying your dues. What helped me is getting things close before heat treat, then after heat treat things are much more controllable when grinding. I am just trying to point out that perfection can be achieved doing things free hand if one has the desire.
Clint
 
Jason,
Remove your Platen and round the shoulders just a little on both sides evenly. Also run your belts over the sides and break them with a piece of Crock stick, Broken China or tea cup, or the ceramic of a old spark plug. You want to feather or slightly tear the edges of the cloth of the belt.

Laurence

www.rhinoknives.com
 
rhinoknives said:
Jason,
Remove your Platen and round the shoulders just a little on both sides evenly. Also run your belts over the sides and break them with a piece of Crock stick, Broken China or tea cup, or the ceramic of a old spark plug. You want to feather or slightly tear the edges of the cloth of the belt.

Laurence

www.rhinoknives.com
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Hi, Laurence,

I too have the same problem. When you said "round the shoulders", do you mean rounding the shoulders of the sanding belt by breaking them with Crock stick? Or there are two different steps. To what degree do I break the sides? ( With the platen off, I assume?)

The method you shared is exactly what I need to follow, just want to make sure I understand a bit better. Again, thanks for sharing.

Jerome
 
If you are tight on $$ (and who isn't?) and you cant understand how you can get $120 worth of use out of a file guide, my advise would be "TRY ONE" ask for one at Christmas, a birthday, fathers day whatever! I have never had the success cutting blade bevels as I do now. Is it a jig, or a crutch as some would say, yes. Does it matter? If you like getting a much better grind, to me,no. I'll make you a deal, if you purchase a BB carbide file guide and don't like it, I will gladly buy it from you for what you paid as long as it is in used as new condition. Using a file guide wont make grinding foolproof ( I can attest to that!) but it will help correct what is a failure point for a lot of us!

God Bless
Mike
 
datoudaw said:
Hi, Laurence,

I too have the same problem. When you said "round the shoulders", do you mean rounding the shoulders of the sanding belt by breaking them with Crock stick? Or there are two different steps. To what degree do I break the sides? ( With the platen off, I assume?)

The method you shared is exactly what I need to follow, just want to make sure I understand a bit better. Again, thanks for sharing.

Jerome
Click to expand...

First you want to just slightly round the corners of the steel platen. Then you want to break the edges of the belts with the crock stick.

Laurence

www.rhinoknives.com
 
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