why not sharpen on a belt grinder?

I agree a belt grinder is a better fit for some things and by hand is a better fit for others. If I am sharpening only 1 knife I use my bench hones. However if I am doing more knives I use the belt grinder. If I want my very best edges I also need to do them by hand and it takes time to do for me. That said I feel my leather belt edges are more than really good and I really only go for my very best edges less and less these days. Truth be said the super duper edges I like to brag about aren't what I put on my user knives anymore anyways.
 
A wag based on my observation....ymmv.

I found affect of edge rub by leather or linen strop or belt form, surface coated with high-temperature wax-based plain or abrasive compound, lists below with estimated percentile of significant.

60% - blade surface smoothing due to wax coating & filling. Actually provides smoother glide (via lower friction) when cutting. Rate of smoothness loss depend on material and speed(heat) of cutting.

20% - apex rounding. a thinner apex the more it flexes, so substrate at relieve-edge reach up and round it up until rounded apex is actually stiff enough to resist the upward push. Certainly it is equiv to a convex micro bevel, thereby more durable apex, albeit goes along with nano/micro wedging (may not perceivable by user... yay, an easy won cake!).

10% - burnishing. which only applicable to steels with high to moderate amount of ductility/plasticity. This because most abrasive size of this type of application has large diameter, so the interaction has low impulse forced because of substrate low yielding (leather/linen flex). For other steels - this percent is lower, thus delta contribute to rounding and abrading

5% - abrading/shaping w/o rounding. This percent is small because in my many attempts, I need abrasive that sub-micron + sharp/fresh + very high speed (watch the heat).

x% - others

For fixed 1-10um abrasive belt, wag: [abrading, burnishing, rounding] == [50, 25, 20,others]
 
HeavyHanded said:
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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You built your grinder yourself right? Where did you get the motor for it. I have looked for a slower DC motor but the best I usually find is 1750 rpm. any slower and there isn't enough torque to really use it on a grinder. Your setup sounds like it would be fantastic.
 
cap'njake said:
You built your grinder yourself right? Where did you get the motor for it. I have looked for a slower DC motor but the best I usually find is 1750 rpm. any slower and there isn't enough torque to really use it on a grinder. Your setup sounds like it would be fantastic.
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Haven’t used one personally, but on another forum, I read some we’re getting a motor from “Penn State Industries” to make a variable speed sharpener. (HeavyHanded may have a better option).
 
cap'njake said:
You built your grinder yourself right? Where did you get the motor for it. I have looked for a slower DC motor but the best I usually find is 1750 rpm. any slower and there isn't enough torque to really use it on a grinder. Your setup sounds like it would be fantastic.
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I actually scavenged mine from some equipment that was being scrapped at work. I pulled the controller, switches, and added a switch to reverse the current so it can run backward if I want. Is a 7 amp motor, 225 continuous oz/inches (whatever that translates to), it has a lot of torque for its size. I can pull the rest of the info if you want, still has the OEM tag.

I've been wanting another just like it but haven't been able to part with the $. Looks like it'll be about $300 to get a good one with a controller. If you find a better deal let me know!
 
All right will do. I would love to build me a nice little sharpening grinder. money has been the biggest hold back for one. I would like to have it water cooled too.
 
cap'njake said:
Where did you get the motor for it. I have looked for a slower DC motor but the best I usually find is 1750 rpm.
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I haven't tried this, but I read somewhere that a motor from a treadmill makes a great variable speed belt grinder motor. Seems like it would have plenty of torque, even down low, since it has to be able to move ~300 pounds of human being on a belt, even at it's lowest speed.

Brian.
 
bgentry said:
I haven't tried this, but I read somewhere that a motor from a treadmill makes a great variable speed belt grinder motor. Seems like it would have plenty of torque, even down low, since it has to be able to move ~300 pounds of human being on a belt, even at it's lowest speed.

Brian.
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That's a fantastic Idea. Never even crossed my mind.
 
cap'njake said:
All right will do. I would love to build me a nice little sharpening grinder. money has been the biggest hold back for one. I would like to have it water cooled too.
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When running at low RPM I just run a wet drywall sponge on the belt for a few seconds - cleans a lot of swarf off and keeps the belt wet. I normally run just fast enough to sling some water but not enough that it all flies off as its being applied.

I've heard the treadmill motor idea before too, I might be able to find one of those....I'd like to build a 2x48 or 2x72.
 
shopping list for any one thinking about building their own rig
http://www.electricmotorwholesale.com/LEESON-113026/

http://www.electricmotorwholesale.com/9543-KBDA-27D/
http://www.electricmotorwholesale.com/9543-KBDA-27D/
I 'm using a 2x48 " from Norm Coote
http://www.cootebeltgrinder.com/index.html


finished rig
DdTwkXRcKt0fe-E1opWKS0I72r7Mql0_JMbQODQ_ADxNeN2uBeJsh_qnXFYaEBte7XBixZej2Z6fd_MhKA=w184-h275
 
I would think the cheap Harbor Freight 1 X 30 belt grinder could be used with a simple rheostat.
If that's the case, HF also sells a dial-type rheostsat as a "router speed control."
I used one of these rheostats with my Unimat lathe. Worked great.
 
Bill DeShivs said:
I would think the cheap Harbor Freight 1 X 30 belt grinder could be used with a simple rheostat.
If that's the case, HF also sells a dial-type rheostsat as a "router speed control."
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It'll burn out the motor of the HF sander.
 
Bill DeShivs said:
Why? The motor doesn't have a starter.
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It has to do with the type of motor ("brush vs brushless"). It was tried a few years back, and was brought up after a couple of testers said their motor failed... that it has the wrong type of motor to use it on.
 
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cbwx34 said:
It has to do with the type of motor ("brush vs brushless"). It was tried a few years back, and was brought up after a couple of testers said their motor failed... that it has the wrong type of motor to use it on.
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That's what it comes down to. What I'm reading about the Unimat Lathe suggests it used a brushed motor, a.k.a. a 'DC' motor at low horsepower (like 1/10th HP). Same type of motor design as used in routers, circular saws, vacuum cleaners, corded electric hand drills, etc, utilizing the 'brushes' to rectify the incoming AC supply to a 'DC-only' current to the motor windings. The rheostats often sold as 'router speed controls' are made for brushed motors; if so, the rheostat is probably OK on that lathe. But, I don't think the newer grinders at HF & elsewhere are using brushed motors, instead using AC induction motors. Hence the possibility of damage, if they're strictly an AC induction motor, as most grinders seem to be these days.

Some very small bench/tabletop 'miniaturized' versions of grinders, made exclusively for small hobby work (model building, jewelry work, etc) are still using low-horsepower DC (brushed) motors; but those are kind of limited to that niche market. I have a small hobby drill press along the same lines, with it's own built-in speed control on a DC, brushed motor; unlike the benchtop Craftsman drill press in my garage, which uses an AC induction motor (1/2 HP).


David
 
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I see. I just remember that my 1 X 30 has a dinky little motor, and thought it was worth mentioning.
I have 3 2 X 72 grinders, so it isn't something I need. I haven't used the 1 X 30 in years.
 
Bill DeShivs said:
I would think the cheap Harbor Freight 1 X 30 belt grinder could be used with a simple rheostat.
If that's the case, HF also sells a dial-type rheostsat as a "router speed control."
I used one of these rheostats with my Unimat lathe. Worked great.
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I did this.. You can slow the speed but you have no torque, the belt stops with little pressure applied.
I dunno about it killing the motor as I stopped using it pretty quickly.
 
Some day, when I'm a big boy and I'm all grown up, maybe I'll have a belt grinder like Ken.


Three HP motor on a Coote grinder. Looks super awesome.

Brian.
 
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