How to not blunt the tip with a belt sander?

[foxyrick]

I got a cheapy belt sander the other day, 1" x 30", and my infi is forming a queue!

Thing is, I've been practicing a bit on other blades and so far have managed to slightly round the tip on every one! They are scary sharp though, not that they weren't before, it just took seconds instead of half an hour.

So, what's the technique when going convex on a belt sander?

P.s. I know not to let things get too hot etc.

 

[JParanee]

Do not run your tip off belt. Stop knife before the tip slides off belt.. Take it easy you are takeing to much metal. should strop or sandpaper for light sharpenin save belt for really worn or reprofileing blades.

 

[foxyrick]

I'm reprofiling. I've only used a very light touch, on a 600 grit belt. It sure does remove metal fast even so. Probably just more care required I suppose.

I could finish the tip by hand; I did my whole FBM by hand it just took hours!

 

[Bigfattyt]

Another thing I have seen on tutorials is to make sure that as you progress to the tip, you keep the the edge perpendicular to the ground, and try to make sure you are not pulling the handle out toward your self as you rock it up to keep the edge perpendicular to the ground.

I have never convexed an edge yet with a belt sander. I just picked up a harbor freight 1x30 + 5 inch disk combo belt sander. I am in the midsts of convexing my FBMLE by hand on sandpaper (will take quite a few hours because the edge is so long, and the profile quite thick, not to mention that the v grinds are not of even height along the whole blade, and not symmetrical from side to side).

I will have to get that belt sander set up in the garage and give it a whirl at convexing on one of my cheap cheap cheap knives. First, I will have to use it to finally finish up the handle scales on my first home made knife.



I am sure that real experienced people will chime in soon to help you out further.

 

[safetyman]

I have just posted some pictures of what I came out with when I sharpened two new knives I recently bought.

http://www.bladeforums.com/forums/showthread.php?t=603175

I am new to belt sharpening and I started out with relatively expensive knives (Dumpster Mutt, Scrapper 6, Dog Father) but I made sure to do a test run with a Cold Steel Master Hunter first to just get the feel of the movement. I have since sharpened and re-profiled most all of my blades. Like BigFattyt said, I found that keeping the edge perpendicular to the ground makes for a cleaner edge profile (even edge height over the length of blade).

To not round the tip (I did that with the Master Hunter), don't sweep the knife off of the belt at the end of your stroke. Just stop with the tip in the middle of the belt and end there. Be cautious not to leave the tip there even for a few seconds because a thin tip can get burnt real easily (I also did this with the Master Hunter).

What also helps is to start with higher grit belts so you don't remove a whole bunch of edge before you get the hang of it and are able to do it right. I started out with 1000 grit just to be safe and once I felt safe I moved it on down. I'm currently at 400 grit which I think is a great re-profiling grit, then I use a stropping belt loaded with Craftsman green rouge.

If you visit my thread you can see that 400 grit with a stropping belt can get you some decent results. Even I was impressed because the knives in the pictures were only the 7th and 8th knives I sharpened with belts ever. It really is an acquired feel and I'm not saying I know everything but it'll come to you as you sharpen more and more. But maybe you shouldn't start with INFI... .

 

[foxyrick]

Thanks guys.

Safetyman, I'll have a look at your thread tomorrow (I'm off to bed now), thanks for that. By the way, your sig line made me laugh!

 

[Kiah]

I'm the opposite of Bigfattyt. If I try to keep the edge parallel to the ground, I'll round it every time. I keep the blade at the same level and angle the whole time. When I get to the belly leading into the tip, I pull the handle back slightly as I come up on the tip.