Help a Newbie With Plunge Lines

J

jmackle

Joined
Jan 29, 2015
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Hey guys, I'm looking for some advice regarding plunge lines. I've only started attempting the knife making thing and things have been pretty smooth due to all the info I get on here/youtube/books/etc. The biggest problem I have right now (only made 2 knife blades so far) is that the plunge lines are very sloppy. My set up is that I have a 1x42 grinder and and trying to learn how to grind the bevels free hand. So, short of "buy a better grinder" or "use a jig", any advice you could give me?

What advice would you give a rookie when it comes to plunge lines?

For reference, my biggest problem is that the lines just don't seem to be cleanly cut. Should I try and set them with a file? Where should the edge of the belt sit relative to the edge of the platen? (plum?, outside the platen?, inside?).

Thanks guys,

jmackle
 
I do it two ways. 1 is to set the belt to the edge of the platen and grind both sides. You can make or buy a carbide guide to clamp on the blade so your plunges line up on both sides. This makes the transition from plunge to bevel pretty much 90 degrees. It also makes it more difficult to over shoot the plunge. After I get close to my finished bevel at my most corse belt I hang the belt over the edge of the platen about a 1/4". This will taper the plunge, which I prefer. 2 is to hang the belt off 1/4" the whole time. I find this a little more difficult to keep both sides even but it may just be me. If the belt is new, especially with ceramic belts, you may need to break the edge so it's not so stiff. To do this just hang the belt off and take a scrap piece of steel and fold the edge over while it's running. I've heard of folks using a chainsaw file to cut the plunges and then grind to them but I've never tried it. Hope this makes sense and helps. Also make sure you use fresh belts. You will hear lots of folks say "use them like they're free". The sooner you do this the better off you'll be.
 
I'm still a rookie myself but what I've found helps me is to keep my shoulders strait elbows in and move with my body. Helps me keep things as accurate as possible when lining up my plunges.
 
You can file in your bevels with a chainsaw file then clean them up with belts. Much easier to control their look
 
Here's a great way to get that perfect symmetry and finish in the radius.

[video=youtube;fA4BVvfV3tQ]https://www.youtube.com/watch?v=fA4BVvfV3tQ[/video]


Edited to add: I forgot he doesn't actually show himself using that set up in that vid. Watch the vid below to see how he uses the file guide and the block with sandpaper to dial in his plunges. That specific part starts at 10 minutes in. :)

[video=youtube;vZE5P6TYCdU]https://www.youtube.com/watch?feature=player_embedded&v=vZE5P6TYCdU#t=626[/video]

~Paul
My YT Channel Lsubslimed
 
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You can easily make your own file quide/plunge line guide by taking some thicker stock blade steel and cutting it into around 3" long by 3/4" wide pieces. Drill some holes in them near the end of each side, bolt them together, then grind them flush with eachother so they line up perfectly with eachother. It is easier to dirll two hole in one of the pieces, then use that as a template to drill the holes in the secod piece.

After that, do a quick heat treat on them, and only temper at about 370 F a couple times to keep them on the harder side. Afterwards bolt them together agan to make sure they still line up perfectly, if they don't (due them warping a very small amount during the heat treat) then slighly grind the edges til they are lined up. Then you can attach it by bolting them on the ricasso of your blade and use while grinding or filing in the plunge lines. Basically a very simple version of what you see in the video above. Since they don't have carbide faces, you will wan't to check them everytime you used them to make sure they like up, as they will get ground into a bit if used while grinding.

~Paul
My YT Channel Lsubslimed
 
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Before spending the cash to buy a file/grinding guide, I'd suggest that you simply wrap some tape around the tang to designate where the plunge should be located. Keep the tape on there while grinding bevels on both sides of the blade. Pay attention to keep the edge centered on the blade thickness.

I've tried grinding with a "file" guide and they are too bulky and get in my way. Many others have have stellar success with them. Considering your 1x42 grinder, it may be your best bet. But try with the tape first. I think it will drastically improve your finished product.

Otherwise, finish your plunges with a file.

Mike L.
 
Another thing you can do is not try to get the matched up until after heat treating your blade and then only at 220 grit. As fast as your grinder spins any lower grit will get you into trouble fast. And like with every other skill in knife making practice, practice, practice.
 
I'm new at this too but I use a sharpie to mark them exactly where I want them to be on both sides and both edges then take care to line those up with the edge of the belt on the first few passes to get the plunge established. I've been tracking the belt right on the edge of the platen, but I'll have to try hanging it over for that nice curved in look.
 
I'm new at this too but I use a sharpie to mark them exactly where I want them to be on both sides and both edges then take care to line those up with the edge of the belt on the first few passes to get the plunge established. I've been tracking the belt right on the edge of the platen, but I'll have to try hanging it over for that nice curved in look.
 
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