How would you sharpen X?

[Luftmensch]

That kind of speed is so unthinkable, it hurtz.

I am glad somebody is making these comments periodically!

Edit: Bad pun aside, I just realized I have no idea what 90 hz means. So this is like 5400 rpm.... which I guess is kinda fast? But idk. I'm not smart enough to know what rpm I'm working with. I just set things to slow or medium or fast. Maybe I should work this out at some point.

Your belt speed is almost certainly controlled by a VFD... a variable-frequency drive. This device converts your mains AC signal into a DC signal and then back into an output AC signal. The speed knob on your controller changes the frequency of the output AC signal connected to your drive motor. Basically Hz = RPM. By twisting the knob to 11 you get more speed.

Sweden has a grid frequency of 50Hz

 

[HumbleHomeCook]

Somewhat related to the thread recency:


I say this because of something in the comments of the vid:

philipp594
11 hours ago
Why do you not rough grind it first, when annealed, then harden it and do the last little bit? Would it shatter during hardening? Or bend?

REPLY

Big Brown Bear
11 hours ago
How about I ask you, do you think that having areas of thicker and thinner on the blade would change how the same time and temperature are affecting the different sized areas during austenitizing and cooling? Also do you think there would be concerns about decarburization and warping? There must be a good reason why I am willing to spend more time and money to grind from full thickness eh?

****

So Shawn does all his grinding post-HT. I believe he sets his edge bevel on the belt as well and then finishes by hand so it might not be fair info to toss into the mix. It just popped up in my feed and reminded me of this discussion.

 

[ian]

Your belt speed is almost certainly controlled by a VFD... a variable-frequency drive. This device converts your mains AC signal into a DC signal and then back into an output AC signal. The speed knob on your controller changes the frequency of the output AC signal connected to your drive motor. Basically Hz = RPM. By twisting the knob to 11 you get more speed.

Sweden has a grid frequency of 50Hz

This is a funny post. I'll get around to figuring out what RPM "100" corresponds to on my grinder one of these days.

In related news, I actually used my grinder at 60% speed for the first time today! Maybe in 5 years I'll actually use it on full.

 

[crockerculinary]

To me that is a super useful takeaway. 300f is hot. I know what touching something 300f feels like. 300 burns fingers. So, let’s say I could have an infared thermometer pointing at the contact point of the knife/ belt, if I never hit 300, I wouldn’t have any issues?
(They way I use the belt I can’t think of a time where any point on the knife was on the belt for more than a second. And if it starts to get warm at all it gets pulled and dipped.)

 

[Troopah_Knives]

To me that is a super useful takeaway. 300f is hot. I know what touching something 300f feels like. 300 burns fingers. So, let’s say I could have an infared thermometer pointing at the contact point of the knife/ belt, if I never hit 300, I wouldn’t have any issues?
(They way I use the belt I can’t think of a time where any point on the knife was on the belt for more than a second. )

It's a bit more complicated than that. It's a game of thermal mass. The edge is very small and so heats and cools very quickly so dumping a small amount of heat (grinding) into the edge can raise the temperature significantly however it's not enough heat for you to feel or get injured. For an example of this phenomenon think grinding sparks which are easily 2000f+ cant burn you because they are so small they can't transfer enough heat to your skin. So just because an edge feels cool doesn't mean that it didn't reach a high enough temperature to over temper.

On the topic of infrared thermometers. Sure that would work in theory if you got one that read the temperature of a small enough area. Usually, they read about a 0.5"diameter area but you would need one small enough that it would read just the apex of the knife.

Finally, It sounds like your current sharpening method would pass the test of the study that was done above. However, that study doesn't control well for thermal mass. Adding the lacquer to the edge basically acts as a heat sink for the very apex of the blade meaning the grinder needs to heat up much more material in order for the same temp to be reached at the edge. Basically, I would interpret their results as a best-case scenario. 1-2s will definitely overheat your edge. Less than that? Maybe maybe not. I hope that clears it up.

 

[ian]

To me that is a super useful takeaway. 300f is hot. I know what touching something 300f feels like. 300 burns fingers. So, let’s say I could have an infared thermometer pointing at the contact point of the knife/ belt, if I never hit 300, I wouldn’t have any issues?
(They way I use the belt I can’t think of a time where any point on the knife was on the belt for more than a second. And if it starts to get warm at all it gets pulled and dipped.)

I don't think that's the takeaway. The IR thermometer won't be able to measure temp right at the apex. The point is that there's no way you'll really know if the apex gets superheated, so you should be over-cautious if you're finishing your sharpening on a belt. It might be fine if you're just making sure that the blade doesn't get too hot to the touch, but it also might not be fine, so err on the side of over-cooling, at least if you're prioritizing good edge retention over time required to complete the job.

 

[crockerculinary]

Got it, got it. I sure wish there was some way to know for sure if better technique on belts was able to avoid this. Is there any not ridiculous way to test this? I would really like to have a practical answer for whether or not the way I am using belts is able to avoid damaging the steel.

So are we convinced that water cooling methoda on belts controls this?

 

[M1k3]

Somewhat related to the thread recency:


I say this because of something in the comments of the vid:

philipp594
11 hours ago
Why do you not rough grind it first, when annealed, then harden it and do the last little bit? Would it shatter during hardening? Or bend?

REPLY

Big Brown Bear
11 hours ago
How about I ask you, do you think that having areas of thicker and thinner on the blade would change how the same time and temperature are affecting the different sized areas during austenitizing and cooling? Also do you think there would be concerns about decarburization and warping? There must be a good reason why I am willing to spend more time and money to grind from full thickness eh?

****

So Shawn does all his grinding post-HT. I believe he sets his edge bevel on the belt as well and then finishes by hand so it might not be fair info to toss into the mix. It just popped up in my feed and reminded me of this discussion.

He also grinds wet. He uses a water spray system to cool the blade down.

 

[HumbleHomeCook]

He also grinds wet. He uses a water spray system to cool the blade down.

Very good point!

 

[Troopah_Knives]

Got it, got it. I sure wish there was some way to know for sure if better technique on belts was able to avoid this. Is there any not ridiculous way to test this? I would really like to have a practical answer for whether or not the way I am using belts is able to avoid damaging the steel.

So are we convinced that water cooling methoda on belts controls this?

There absolutely is. Using the methods that @Larrin used in his study and a much broader range of tests (different belts, speeds, cooling, etc) we could get a better idea of what's going on. Unfortunately, that would be a huge amount of work and the testing may be prohibitively expensive.

Water-wise: I'm sure it's not perfect but it should help a lot.

 

[Bico Doce]

I personally cannot add any insight to the effects of belt sharpening on edge quality but I just came across this section on exactly that in Dr Vadim’s book - Knife Deburring.

edit: pg 53 - 54

 

[Rangen]

The diversion to powered sharpening on this thread is very interesting. Not directly applicable to me -- I don't power sharpen, because I enjoy using hand tools, and don't enjoy using power tools, though of course I recognize their irreplaceable worth when needed.

The main question it raises in my mind is: will @ian now buy a Tormek? Or, even better, one of those massive grinding wheels you see in Japanese knifemaking videos, with a stream of water running over them all the time? If the latter, I want pictures.

 

[ian]

Those water wheels are super cool. Props to sharpeners (like @JBroida?) that use them.

 

[M1k3]

Those water wheels are super cool. Props to sharpeners (like @JBroida?) that use them.

Quick fix! Garden hose and a spray nozzle!

Or do it the real way like BBB did...

 

[ian]

Or do it the real way like BK did...

Fixed. But yea, having one of those sprayers like BBB is my new goal.

 

[Dominick Maone]

https://www.bladeforums.com/threads/kool-mist-misunderstanding.1829025/
BBB is using a kool mist system. Kamon is using flood coolant. Two different things. Check out my thread in another forum about a hose spray nozzle.

 

[Luftmensch]

If it is a problem.... I wonder how much edge (volume) is 'burnt'? Power grinding the primary bevel and finishing on whetstones seems sensible. It had better be... The practice is common enough. Do you have to spend 10 minutes on the whetstones removing the ruined temper.... or 30 minutes?

... obviously the answer depends. But let's say the edge was never uncomfortably hot to the touch.... Surely the amount of material that was cooked (if it cooked) will be tiny?

 

[Brian Weekley]

Interesting subject. For those who are interested I found this video worth watching.



I’ve been a “home” sharpener for a long time and my techniques have evolved over time. As my eyesight has deteriorated I find myself sharpening by ear a lot of the time. Anyway here’s where I’m currently at. Victorinox and “German” steel knives get the Tormek. I may finish them with a few stripes on a 2k stone if they didn’t come to me abused and beat up, but that’s it. Artisan and Japanese knives get the stones, generally 400 grit (if they need a bit of thinning) to 6K … whatever is necessary. Currently I love using JKI’s 1k-6k vitrified Diamond stones, especially on harder steels. Edge angle depends somewhat on the steel and the condition the knife arrive in. I charge a lot more for sharpening on the stones. I don’t do folders, scissors or chisels. Is my way the best way … not that I would claim. I’ve bought quite a few knives. I’m amazed at the quality of the edges that have arrived on knives I’ve purchased from some KKF members. There are some members on KKF who are really capable of putting edges on blades … probably using stones.

I’ve never used a belt sharpener. I watched the previously mentioned video with Ryan Swanson and was “gobsmacked” at the facility with which he used his belt grinder. Free handing in a way the caused the hair to stand up on the back of my neck at times. Power sharpening is, in my opinion, dangerous for me. I have to pay a lot more attention and concentration using the Tormek than I do using stones, especially in edge leading mode. In the process of doing my time with TF’s I bought two knives from District Cutlery … a petty and a 195mm nakiri. I paid Ryan to “thin them as he thought necessary“. He did a pretty good job. They arrived scary sharp and nicely thinned … a more consistent job than I would probably do using stones. Has the edge of the blades been adversely affected? Only time will tell whether TF’s great edge life has been affected, but I don’t think so.

I’ll probably never use a belt sharpener. I don’t think I have the energy at this stage in my life to deal with the learning curve. I’m happy with the results I get from my stones. I would, however, be uncomfortable turning a quality blade to a sharpener who uses a belt sharpener. Skills differ and it seems to me that the primary reason for a sharpener to use them (apart from putting an initial edge on a new knife) is speed … sharpening more knives at less cost For more revenue. That’s not my thing and I’m not depending on income from sharpening for my daily bread.

 

[Bico Doce]

Victorinox and “German” steel knives get the Tormek.

A Tormek looks like a lot of fun to use. Just out of curiosity, how do you maintain the angle on the Tormek as you approach the tip of the knife assuming there is a belly/upsweep to the blade?

 

[Brian Weekley]

A Tormek looks like a lot of fun to use. Just out of curiosity, how do you maintain the angle on the Tormek as you approach the tip of the knife assuming there is a belly/upsweep to the blade?

I keep the Tormek set at about 22 degrees. This seems like a good setting for the types of blades I sharpen using it. I raise the blade away from the stone as I reach the curve towards the tip … just as I would using a flat stone. In this way I maintain a more or less constant sharpening angle blade to stone.