Plunge Line Woes

P

PrinceVlad

Joined
Jan 28, 2021
Messages
2
Hi Guys

Since I became interested in knife making in December, I've been a lurker here. Since then I made 3 knives, although I've only had access to mild steel. I'll be getting some 5160 next week.

I have all the basic tools including a Ryobi 1x30 belt sander, files, drill, angle grinder, and sanding paper. My problem is that, with the belt sander, the plunge lines are deeper than the rest of the bevel. (I use a jig) And I can't sand the grinder marks inside the deeper part out.

Any idea what I'm doing wrong?

Thanks
 
There can be many causes, but most likely is you are trying to start at the plunge, or staying there for too long.

Walk the blade toward the plunge and then reverse direction away from the plunge. Don't linger. Once the basic plunge is made, use files to trim it up as needed. Many small shallow passes do much better than one or two deep ones.
Also, there is a tendency (especially on a 1" platen) to "twist" the blade into the plunge to make it crisp. This cuts deeper than you want.

Second - Leave some meat for hand sanding. Your 1X30 isn't the greatest thing for accuracy. Take the bevels down to about 80% and then finish with sandpaper wrapped around a block of aluminum or very hard wood. Change the paper frequently. Dipping the block in a bowl of soapy water is also a good idea.

Finally - A carbide plunge jig is money well spent. Most of the knife suppliers sell them.
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You might be starting at the plunge with the rest of the blade not square to platen so it cuts in deeper there. Try what Stacy suggested or make sure you're totally square with the blade in contact with the whole 1" width if you're going to start at the plunge.
 
just make sure your pressing it flat against the platen and that your not holding it there too long. you want to start moving the blade as soon as u touch the platen.
 
I found it super difficult to get decent plunges on the 1x30 had issues with low points as well. The narrow flex able platen is so easy to move off from perpendicular.

I started filing my plunges in with a chainsaw file before I hit the sander. Was a pretty easy way to get a nice clean finish.

Sooooo much easier on a 2 inch platen
 
Thanks Guys.

I'll try it with the next one. Even though I'm getting better steel next week, I think I'll stick to the mild steel for now just to get the practice. And this is purely due to cost considerations. I'm from South Africa and here I pay about $10 for 18 feet of mild steel flat bar while the 5160 is about $16 for 3 feet. 1085 is about $30 for 3 feet.

Is there much difference in working them?

Now, I have another question. How do you get nice crisp bevel lines. I like the look of them as they come from the belt, but when I sand, it blends them in.

Sorry for all the questions and thanks for the help.
 
I wrap a metal file with sand paper for sanding but you can use a piece of hard wood also and that will keep the plunge lines crisp.
 
I find a 3"X3"X1" block of aluminum works just about perfect. If you want, hollow grind the sides to give a better grip. A 2"" or 3" contact wheel works good for this..
A heavy rubber band from the produce department is perfect for holding the paper on the block. They use these to bundle broccoli and asparagus (ask the produce manager, they will give you some free).

Cut your 9X11" abrasive sheets of paper into 3"x5.5" wide strips. The strip will wrap around the block just right. Place these strips in large zip-lock bags. Store all the bags in a plastic bin.

Even better than cutting up sheets of paper is using shop rolls of abrasive paper. They store neatly on a rod and just tear off a piece as you need fresh paper. Buying a 2" wide 50 foot roll of 120, 220, 400 grit will take care of all the coarser sanding steps. Your entire stock of abrasive paper will hang from a shelf and take up half the room of a roll of paper towels. If you use 2" shop rolls, make the block 2X3X1". You pay for the convenience, but they are affordable from the right source.

Economy Tip:
Klingspor sells big bargain boxes of odd width/length 100-400 grit rolls in 20 pound boxes. This is a very good deal. Buy one or two when they are available. Unlike belts, they don't go bad with age. You will find a use for every roll in the box. A 20 pound box costs what one 2"x50 foot roll costs from Tru-grit.
Klingspor's World Famous Bargain Box, 20lbs of Lathe Project Cloth Rolls | Klingspor's Woodworking Shop
 
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