Noob Sandpaper Question

Trout Hound

Trout Hound

Joined
Sep 28, 2014
Messages
693
Howdy Y'all,
I'm new here, and tried doing a search for this info, but didn't quite find what I was looking for. Please forgive me if this has been covered to death and I just didn't find it.

I've been experimenting the last few months sharpening knives with sandpaper on 1/4" plate glass. So far, I am quite impressed with the results. I have a few questions though:

1. Most of what I see written about this method applies to chisels or plane blades, but I seem to be getting good results on knives by adhering the paper against the edge of the glass so that I can use it like a bench stone. I am able to make edge-leading strokes without an issue. I'm just wondering how many others use this method for knives, and if I am losing any edge quality as opposed to using a bench stone or other commercial sharpener. I've been thinking of picking up a DMT Aligner clamp to help keep edge angles uniform, when desired.

2. I have been using 80x AlOx paper for reprofiling, and I am quite impressed with the cutting speed. I usually then go down to 320 wet/dry and just finish there. I like some tooth in the blade for most tasks, and this seems to get things shaving sharp with some tooth left. Does this sound like a good method?

Happy to hear any other tips you have. Most of the sharpening I do is on folding and fixed blade knives for EDC and camping/bushcraft tasks, with the occasional kitchen knife thrown in. For EDC and outdoors, I usually shoot for about 30 deg. inclusive, closer to 20 for kitchen slicing knives.

Thanks!
 
Yeah, plenty use sandpaper. Get yourself some 600 grit, it will still be plenty toothy but your edge will be finer.

I'm still happy with how much bite I get with 30 micron polishing paper
 
I've been doing s'paper on glass for 15 years, use it for e'thing-- sharpening, reprofiling, modding, polishing, see no reason to change. I stock Norton W/D 220 to 2500, plus McQuire 3000. There's nothing you can't do on glass, you just have to learn to keep the cutting edge on the same plane thruout the process to keep your angles consistent-- just like a stone. Less Mess.
 
if its working for you, then by all means, develop it and work at it. I think most guys use stones just because most often its what we learned on. I've used abrasive film for razors, and its worked well, and used sandpaper for reprofiling or convexing. I think over time, especially with a large number of knives, it may become more economical to get stones, but with that being said, the skills and methods you develop should directly apply, since you have to be quite gentle with the sandpaper, that should serve you well if you start using stones, especially softer water stones.
The only other thing i could think of is that 320 seems still very course, I think you would be well served to at least experiment with higher grits, even up to 2000-3000 and see where you like the edge to be. the advantage is that you could buy a few sheets every 500 grit, and it would be like owning a large set of stones.
 
Per Heavyhanded's recommendation use a large pencil or gum eraser to keep your sandpaper clean and from loading up with swarf. This will prolong use and life of sandpaper. I also use 3M Spray Mount artist's adhesive (cat # 6065) to temporarily glue my paper to wood or cardboard backings. I have not yet tried glass boards for backing. As the grits break down and become finer my older sanding boards get regulated to less of a sharpening duty to more of a polishing duty.
 
Thanks for the input guys, please keep it coming. What grit sandpaper does everyone use for reprofiling? Is my 80x paper too aggressive? Also, should I stick to wet/dry only? The 3M general purpose paper in 80-150x seems to work okay, but maybe there's something I don't know. Am I okay skipping grits, say 320 to 600, or would I be better off to hit all of them? Sorry, I'm full of questions. Thanks!
 
For reprofiling I'd stop at 120 unless absolutely necessary. Also I'd stick with SiC wet/dry. The regular ALumOx sandpapers come in a variety of abrasives that may or may not work well on hardened steel, SiC is very consistent across manufacturers and no variation in abrasive coverage on the sheet (differences between wet/dry and no load papers). Light pressure and clean often.

Skipping grit is going to depend on the steel you're working - kitchen knives and low RC stuff can be run up with large gaps in the process. Harder steels need a proper progression. Unlike a solid stone, where you can apply a bit more force to get a faster cut rate from a stone that is perhaps a bit too fine for the job at hand, sandpaper tends to choke and load up pretty quickly when additional force is applied. Also, even over glass or steel the paper will still have some give to it, so light pressure is imperative to reduce any additional convexing beyond what you would normally get freehanding to a minimum. For heavier reprofiling or repair (anything that cannot be done on 120 grit) I'd personally switch to a coarse stone and transition to the sandpaper for clean-up and sharpening.

I also find a few light trailing strokes after I've deburred really get the most from the process.
 
Trout Hound said:
Thanks for the input guys, please keep it coming. What grit sandpaper does everyone use for reprofiling? Is my 80x paper too aggressive? Also, should I stick to wet/dry only? The 3M general purpose paper in 80-150x seems to work okay, but maybe there's something I don't know. Am I okay skipping grits, say 320 to 600, or would I be better off to hit all of them? Sorry, I'm full of questions. Thanks!
Click to expand...

I've liked 220/320 for reprofiling; sometimes even 400 for smaller & thinner blades that don't need much metal removed.

I'm with HH on avoiding anything very low in grit, if only because the heavy & deep scratches left by it will take a lot of work to clean up, and more so with more wear-resistant steels. Recently, I did experiment with a 120-grit Zirconia Alumina belt from Sears, cutting the belt and sticking it to a board. I used it to grind down the spine/tip of a Buck 301's spey blade (420HC), making it into a spear blade with a lowered and pointier tip. In that application, it worked very well, and pretty fast (maybe ~40 relaxed minutes with the board across my lap, dragging the inverted blade's spine & tip lengthwise and tip-trailing along the length of the 21" belt). I cleaned up the coarser scratch pattern with some wet/dry SiC paper up to ~600/800-grit or so, laid atop a granite reference plate for the hard backing.

Low-wear steels like 1095, 420HC, 440A, etc aren't a big deal, if skipping grits. Also as HH mentioned, the more wear-resistant steels, especially those with significant vanadium carbides (S30V, etc), won't get rid of coarse scratches easily, if the jumps in grit are too wide. On the other hand, something like 420HC or 440A will polish up very quickly, even after re-bevelling on something like 320-grit. Even an aggressive strop of hard-backed denim or linen, with aluminum oxide compound, will strip a lot of the coarse scratches away and shine it up fast.


David
 
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I stock 220 but seldom use, you can do a lot of damage in a hurry. 320 for most of my rough work, incl reprofiling. Sometimes I'll start finer just to get a feel, then back down. Stones are certainly cheaper in the long run, but I just like this method. If you're going to stock a range of grits you want e'thing in between.
 
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