why not sharpen on a belt grinder?

I have no problem with people using belt grinders and jigs to hold the blade at a consistent angle or the stone at a consistent angle. No problem with any power sharpening equipment. Everyone should feel comfortable with their method and be able to produce consistent results. Because if you can't you're doin' wrong or using the wrong method. Some blades cut better with a toothy edge, depending on what you're cuttin' and what you're cuttin' with some blades fillet hair with a mirror polish on a very acute angle on fine grained steel.

The issue I have and it's not really an issue, hey they're your knives, what you do with and to them is your business, I just want to help people have the best edge they can and have it last as long as it can without ruining it. If you're inexperience with a belt grinder or use one with too short of a belt and the wrong speed and grit you can make steel disappear very quickly and odds are what doesn't wear away might most likely may lose it's hardness precipitating a premature demise of the knife's usability. In the end it's your knife and how you take care of and maintain it is your business. When you come here and complain about a knife that you've destroyed and blame it's destruction on the manufacturer or maker it becomes everyone else's.

This isn't directed at anyone in particular just a general observation and my humble opinion. Learning to do something like sharpening freehand can only benefit a person and anyone who says they can't do it freehand just hasn't figured it out yet or doesn't have enough practice.

At this point I can't think of anything else I can add, (I know, hard to believe :D LOL ) without repeating myself so unless someone tags me personally I think I'll just read the updates to the thread.
 
Sharpening with a belt sander without coolant will over heat the edge of many steels. Dipping in water after a pass can cause it's own issues, and the notion of cooling the blade after each pass is backward. Dip the blade before each pass to prevent heating. If the steel is prone to over heating, it happens very quickly, and dipping afterward is too late. I used to recommend sharpening this way, but only do so now with great care. Use of a belt sander can cause many people trouble.

Even practiced users can damage a blades edge without knowing. It won't ruin the blade. It can be repaired with as little effort as one good hand sharpening, usually 2 or 3.
 
Me2 I'll admit I don't really have any facts about this. But I really think the over heating of the edge is for the most part over stated. When I sharpen on a belt I mainly do 1 or 2 passes per side on a 320 belt then the same on a 600 and then move to leather. The blade really doesn't even heat up. I don't even use any water before or between passes. Even a thin slipjoint blade will not get hot. Being careful about heating up a blade should be a concern with any type of sharpening I've even gottin a blade pretty hot scrubbing on a DMT XXC, XC, and C wile reprofiling witch surprised me at how hot it got at the time I did it. My belt sharpened edges don't seem to last any less than my hand sharpened edges and I have a hard time believing they are over heated or that the temper has been burned/wrecked.I don't mean to minimize the over heating of a blade but with just a little common sense and care it shouldn't be a problem.
 
db said:
Me2 I'll admit I don't really have any facts about this. But I really think the over heating of the edge is for the most part over stated. When I sharpen on a belt I mainly do 1 or 2 passes per side on a 320 belt then the same on a 600 and then move to leather. The blade really doesn't even heat up. I don't even use any water before or between passes. Even a thin slipjoint blade will not get hot. Being careful about heating up a blade should be a concern with any type of sharpening I've even gottin a blade pretty hot scrubbing on a DMT XXC, XC, and C wile reprofiling witch surprised me at how hot it got at the time I did it. My belt sharpened edges don't seem to last any less than my hand sharpened edges and I have a hard time believing they are over heated or that the temper has been burned/wrecked.I don't mean to minimize the over heating of a blade but with just a little common sense and care it shouldn't be a problem.
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In many cases and for many steels, that can certainly be the case. The steels I've had problems with specifically were A2, S7, 10xx series, Carbon V from old Cold Steel blades, and a low alloy blade that might be something like 1095CrV. All these had issues when sharpened on a belt sander and power stropped. The whole blade doesn't heat up, just the edge up to maybe 0.015 to 0.035 inches up. That was the depth I saw issues. The issues were not evident in slicing operations, but would show immediately in other use, such as chopping use on cutting boards or cutting light brush, 1/8" diameter or so.

I had knives made from m2 and a Kershaw in 420HC that didn't show any issues from belt sharpening. M2 likely for obvious reasons, Kershaw likely because it was already fairly soft and ease only used for slicing work or work that I'd expect to damage/deform any steel.sander cam

It all depends on steel, use, and user, but even the most skilled with a belt sander can damage am edge. The question becomes, will the user notice?
 
I do a lot post-ht grind (maybe more than 30% of the time) on steels with hardness 64+rc. Fact - grinding heat excess of 350F would soften my blades. For each large batch, I tested one 1mm thick 64+rc test on 3 sections using a slightly dull 120 grit ceramic belt running at std 2x72 40% speed. Pressing thumb behind section 1 to 3 == ~ 0.5, 1, 2 seconds. After 2 seconds, water is vaporizing on wet-thumb and yeah it's blistering. \\

Next, calc avg hardness test these 3 areas. * https://en.wikipedia.org/wiki/Rockwell_scale. HRC = 100-d/2um

#1: unchanged
#2: 0.0-0.5rc lowered. i.e. heat affected is less than 1 micron surface
#3: ~1.0-1.50rc lowered. affected 2-3 microns.

I don't have nano-indentation hardness tester for heat affects on apex when sharpening. Due to very small mass and deflecting(more bounces) at/near apex - my extrapolation for 15dps, relatively fresh/sharp 220+ grit belt at 10-20% speed, grind contact duration ~0.2 second - edge hrc would be unchanged. I sort of (seem so because very ad-hoc) confirmed with whittling dried bone tests. Guessing, a dulled 220+ grit would lower apex hrc by 2-5rc. Anyway, I use belt grinder to set bevel and freehand to sharpen my blades using stones & diamond plates.
 
My technique:
1) Reprofile with 3M A300 CF belts. Anything thicker than an Opinel behind the edge is too thick.
2) Sharpen with 3m A30 CF belts. With practice, it is ridiculously easy to get a shaving edge.
3) Shine the bevel with a 3M micron belt or a felt/cloth belt with chromium oxide. I usually only bother with this when I'm sharpening for someone else.
4) Put on a micro-bevel with the Sharpmaker. The micro-bevel can be refreshed several times before there is any need to go back to step 2.

The CF belts, aka "gator" or "brick", seem to run cooler and last longer than other belts. I think the brick pattern pushes more air around to keep the belt and blade cooler. You don't need a huge variety of belts just some patience and attention to detail. Reprofiling will generate a lot of heat (I quench and take my time) but sharpening with the A30 CFs only takes a few passes once you have your bevel set and shouldn't get the blade too hot. 1095, 8cr13MoV or better steels generally work fine (even cheap Chinese ones). 3cr anything, "surgical" steels and mystery steels don't do very well. A $12 Mora is an excellent knife to learn on and if you think a Harbor Freight 1x30 belt sander and 600 grit belts are going to wear it out in one sitting you should pack a lunch. Or several lunches.
 
Me 2 you've been around here for a long time and I believe you. I just haven't had the same problems. In fact my belt edges for the most part out preform my other edges. Now I can and do get a edge sharpest by free handing on hones but that takes a lot of time and care to do. When my little HF belt s sander crapped out on me a few years ago I missed it so much for sharpening I got a better 42 inch belt grinder. Can I over heat the edge? Sure I could but with a little care it just hasn't seemed to be a problem for me and for the last 10 years and many knives. Am I lucky or skilled or both? Who knows.
 
T. Erdelyi said:
If you're usin' it when you're standin' do your pants fall down? ;)
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Lol no I have a nice double sided leather strop I made next to the recliner I have another hanging on the fridge, one in the truck, one in my toolbox at work, and one in my shop. And I have a belt in the bathroom. I am pretty anal about stropping after using a knife. Usually after about 5 to 10 minutes of using a knife I will stop to give it a few swipes on a strop. I use green Chromium oxide on my strops and the black coarser stuff on the other side.
 
With appropriate skills, one can produce nifty sharp and durable edge using belt grinder. Adding to my prev post - keep in mind, the more wear resistant steel the higher percent of kinetic-to-thermal conversion taken place. Whereas clean plough+abrade+fracture impart lower kinetic-to-thermal, which also giving more time for heat to diffuse in steel.
 
db said:
Me 2 you've been around here for a long time and I believe you. I just haven't had the same problems. In fact my belt edges for the most part out preform my other edges. Now I can and do get a edge sharpest by free handing on hones but that takes a lot of time and care to do. When my little HF belt s sander crapped out on me a few years ago I missed it so much for sharpening I got a better 42 inch belt grinder. Can I over heat the edge? Sure I could but with a little care it just hasn't seemed to be a problem for me and for the last 10 years and many knives. Am I lucky or skilled or both? Who knows.
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If you're not having issues that's great. I was careful not to say will cause damage instead of can cause damage. However, after sharpening that way for years, careful checking showed me I was getting damage when I thought I was fine. I have also learned to sharpen much faster with stones, so it's not a time thing anymore.

Try this. Sharpen a low alloy chopper knife on the sander and then chop a bamboo skewer. If you don't see any dents, you're probably fine.
 
Ben Dover said:
No, but I would consider learning to hunt with a spear a waste of time. T

o me, freehanding is a lot like hunting with a spear.
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Brother, I think you missed the point. If the scopes breaks or fails for whatever reason, and you know how to use your iron sights, you won't go hungry during the time you're without a scope.
Same with the sander, if the sander fails or the power goes out and you have the ability to handsharpen, you're that much ahead.
 
If the world blows up, we'll be out of luck! If not, but it loses all power, the Edge Pro, Wicked Edge, KME, etc. will still work. If we are without those, freehand will work. We'd really, really be out of luck at that point! We'll be eating dirt and grass (and an occasional dying animal)! I don't think I'll be practicing freehand skills tomorrow. BTW: Has anybody tried the new Edge Pro superfine stones? I might try those!
 
Yea, I understand where you're coming from, but that adds up to a ton of money. I've got $50 or less in mine, which leaves more money to buy more knives or survival gear or guns and ammo.

I understand everybody doesn't look at it the way I do, and that's cool. I'm old school.
 
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bluntcut said:
...Anyway, I use belt grinder to set bevel and freehand to sharpen my blades using stones & diamond plates.
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This is 80% of how I use mine, and that's at much lower then the rated speed/output of the 1750RPM OEM motor. Even then I often have a wet sponge handy for the belt. Only if I'm doing a regrind will I be dipping the blade and running at higher RPM.

Even if I sharpen to a burr I finish on stones. In my experience this is actually faster and does a better job, as its a lot easier to do QC on a hand-sharpened edge and a lot easier to do the finish work by hand.
 
Me2 it isn't a chopper but I did your test with a SAK, and a chop stick. I had no problems, or denting of the edge. I long ago realized I wasn't much of a tester or very good at it, so take it for what it is worth. I'm not sure but I beleive even Spyderco uses a belt to put on their edgs and I know they do alot of edge testing I'd guess they would have tested the effects of belt sharpening. As Spyderco edges are known to be good edges I do prefer my own edges over them. Not to toote my own horn but my edges with the belt for me last longer than any factory edge I've ever had. My edges are a very shallow and thin convex edge. Even my freehand on bench hones are convexed. And yes I do alot of my sharpening on bench hones. Going back to a point I made before about heating up a blade with a course bench hone I was watching a video of a guy useing one of the systems. He had a hone with a rod conected to it in each hand and the knife in a clamp. He was moving pretty darn fast sharpening that knife and I couldn't help but think of how hot that edge could be getting. Hotter than my 1 or 2 passes per side on a belt I'd guess.
HeavyHanded I use to do and think the same for finishing my edges. but when I got a leather belt that all changed. I finish all my belt sharpening on it.
 
HeavyHanded said:
...
Even if I sharpen to a burr I finish on stones. In my experience this is actually faster and does a better job, as its a lot easier to do QC on a hand-sharpened edge and a lot easier to do the finish work by hand.
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That !!
 
db said:
HeavyHanded I use to do and think the same for finishing my edges. but when I got a leather belt that all changed. I finish all my belt sharpening on it.
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I have and have used leather, cork and even made a denim belt once to test. Don't get me wrong, they work well enough but when it comes to finish work they aren't quite there compared to what I can do by hand in nearly the same amount of time (if you include the time to swap the belt out and the QC factor).

And don't take this as any knock against them, I use my belt grinder often. I just feel it is a better fit for some parts of the job than others. Once it gets up past the bevel setting stage the time intensive work is done and I can take over with stone(s). I keep them right next to my grinder, so is very convenient.

A related note, I was using mine last night and was testing pressure amounts vs heat buildup and removal rate. My grinder is not typical - top end RPM is about 1200 and I normally run at half of that or less depending. But with light pressure I was able to keep removing steel without heating up the edge, continuous contact of 10 seconds. In fact it wasn't even warm. Stock removal rate went way down as well though.

And point taken about heating steel up by hand. When I was working on improving my freehand speed technique I was able to get blades hot enough it was uncomfortable to keep in contact with my palm just using the coarse side of an India stone - with oil.
 
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