Perfect plunges

Time standing in front of the grinder is #1.

And I want to point out that you need to be VERY careful trying to true up plunge cuts with anything that only makes contact in a very small area... like round files, cratex, etc. They certainly CAN be used, but the problem with this type of clean up is that many folks try to do too much with them. Since they only make contact with a very small area at a time, it is VERY VERY easy to create a wavy surface.

You usually won't see it unless you have a trained eye and great lighting. You can take a blade that has had the plunges filed true.... but the overall bevel not truly feathered into it... wave it around in the light and you will see the light bounce off the wavy surface.

If you are just LIGHTLY removing a few pesky scratches, then stuff like cratex work well.

If you are dialing in the plunges to make them dead nuts even side to side, then I would recommend a steel plate or block that's at least 3" wide, with a radius on the edge that matches the radius you want in your plunge.

You use PSA paper, or spray glue paper and then apply it to the block. Then you can use this to dial the plunges in.

It works VERY well. :)

I can get them even right off the grinder, but I still use this method to clean the plunge up. I clamp a carbide faced file guide on the ricasso when I do it. I didn't in this photo, but I usually do now. It only takes about 10 minutes total, and makes the overall hand finishing go much easier for me. :)

155.jpg
 
Just to clarify, I absolutely agree with Nick. Cratex isn't for establishing or even matching the plunges. It does, however, speed up my vertical scratch removal in this area significantly.

I need to pick up a nice steel block to work with like Nick has. Right now, it's all grinder work to even up my plunges, and it just makes me nervous every time I touch the blade to the grinder. I've ruined too many otherwise good blades when addressing the plunges.

--nathan
 
Wheeler's setup/process above is very similar to what I do, it lets you get as picky as you want with the plunges and will make them absolutely consistent every time if done right. I have a different radius on either side of my sanding block, I like a smaller radius on some knives and a bigger one on others.
It obviously dosen't work with hollow grinds but I got over those a long time ago...I guess one could make a sanding block with a radiused face to match their hollow grinds if they were inclined though.
A strip of masking tape along the opposite edge of the sanding block will keep it from cutting a groove across your bevel, nothing like getting perfect plunges, then finding out you have to work the bevels over again.
 
silver_pilate said:
I need to pick up a nice steel block to work with like Nick has. Right now, it's all grinder work to even up my plunges, and it just makes me nervous every time I touch the blade to the grinder. I've ruined too many otherwise good blades when addressing the plunges.

--nathan
Click to expand...

Don't tell anybody, but mine is a block of wood with a piece of G10 epoxied on top of it. It even has clamping thingies on the sides to hold the sandpaper so I don't have to use adhesive.
 
Ive used prescription bottles on hollows with the edge of the paper broken over. But nowadays between my bump guide, and jflex belt I can get em perrty darn true. I use the water and light to really expose akiller grind or spots here and there that need to be blended either at the machine or by hand.
 
Thank you, Mr. Wheeler, another great idea.
The steel block with sandpaper on it is kind of like a grinder platen with J-flex paper flexed around the edge, running at about ten feet per minute.
Brilliant.
 
Nathan, sorry bud, didn't mean to come off like I was correcting you. I know that you know all that... I just wanted to mention it because I know (from firsthand experience mind you :foot: :D) that it's easy create a wavy surface that actually looks pretty darn good. (to most eyes, ;) LOL ).

Don't worry about getting a monster plate like mine... I used what I grabbed out of the bin. I have another one that's just a piece of 1/2" thick plate and it works every bit as well. I have another one with a pretty large radius, for doing integrals, that I milled out of G11. :)


As a general rule, plunges are a funny thing. They really have little effect on the usefulness of a knife... the plunges could be off by 1/8" side to side, or not even be there, and a knife would still cut. But from a "well executed construction" perspective, they are one of the first things that many makers look at. I think most of us figure if the plunge cuts are dead nuts, then the rest of the knife is probably going to look good after further review.

Specifically for the OP... since he's looking for passing reviews from ABS members, he'll need nice, even, clean plunge cuts. Tight or small radius usually isn't a big concern, but matching side to side with no funky spots is a must. And good on ya for searching out honest, constructive critiques from folks that can really help you grow as a maker. :)
 
No problem, Nick. I didn't take it that way. :D I've had the wavy effect as well, and it's definitely visible if you don't take care of it. I will typically get things dead flat to start with sand paper and a lapped sanding stick. Then, if I've got any pesky scratches, I'll use the cratex in the plunge, being careful to make things uniform all around the plunge with the cratex. Then, it's always back to the backed sand paper to flatten things out again and get my scratches correct. That's why I typically use the fine grit, as it doesn't cut much and the wavy effect is minimal. Then the hard-backed sanding flattens it all out again and removes any waves.

I've got a few plates of micarta that I may try the sanding block with. I just suck at filing in an even radius. I need to get some radius gages.

--nathan
 
You must log in or register to reply here.
Back
Top