Making Kitchen Knives – Part 18 – Etching

I did not include this step in the time measurement last time, and neither will I do so this time. It is about 10-15 minutes per blade and the only way to reduce that time would be to forgo it completely. If I only signed the blades with my logo, I would have made a significant improvement actually, but since I have decided to number them too, I am back to square one time-vise.

I wrote about my logo design in the Rondel Dagger series. At that time it was meant to be maybe only a one-time action, but the design has grown on me and I have decided to adopt it as my new maker’s mark for all my wood and metal projects. When working on my first commission, I have built myself a specialized etching electrode that allows me to etch the logo without having to mask the whole blade, prepare big solution baths or construct complicated barriers holding the etching solution in place.

This time around I have further improved on this and for the logo etching itself I have built myself a new stencil, since cutting the logo in adhesive tape each and every time leads to inconsistent results and is time-consuming. I tried to get my hands on photosensitive foil to make a stencil, but I was unable to find any seller in CZ offering one that is not for copper. And then I realized that my mother has an old silicone kitchen pad that she never uses, so I asked if I can destroy it in the name of science. She said yes, so I took it and I cut my logo in a strip cut out of it with a scalpel. It is water repellent, so the etching solution did not want to get in there, but a drop of dish detergent in the etching solution has solved (ahem) that problem.

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However, another problem persisted. Etching stainless steel works differently than etching carbon steel. When etching carbon steel with FeCl3 solution, all you need to do after the etch is to let the solution sit for a few seconds and it turns the inside of the etch black with oxides. For stainless steel this does not happen. You need to change the polarity of the electrodes to deposit a layer of black oxide on stainless steel. In order to do so I had to remove the crocodile clips and switch them between the blade and the electrode several times, which was onerous and annoying.

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I have performed tests on the piece of blade that I nearly ground through, and here you can see the results of various etching parameters. On the left, the two etchings are with five minutes of etching time, which was needlessly long and has led to etching the surrounding area under the stencil too. I found out that one minute is more than enough for this logo and those are the two upper logos in the middle. And as you can see, they are grey, not black, because I did not change the polarity. All the other etches are various iterations of me playing with the polarity and whatnot.

After this experiment I have spent a fruitful afternoon cursing in the workshop building this highly sophistimacated tool from a scrap of plywood, brass sheet metal, copper wire, and some left-overs of speaker cables.

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I can plug my 12 V DC source in the input (on the right) and my crocodile clamps on the output. When the switch is held to the left, the red wire/clamp is the anode and it etches. When the switch is held to the right, the red wire is the cathode and it deposits metal ions (which quickly turn into oxides). And I can flip the polarity fairly quickly, and I can either make the logo entirely black or just the outline, depending on how quickly and how many times I switch the polarity. It was quite fun, although there is still some factor of unpredictability in the outcome that I was not able to figure out.

So I could go etching the blades that were ready and as a bonus I got good use out of the rest of the silicone pad too.

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And it worked really well. The best results I got with 1-minute held at etching current, then 10 seconds depositing current and then 1 minute quickly switching the polarity back and forth. After that I neutralized the remaining acid on the blade with washing soda solution, rinsed it off thoroughly and that was it. I got some teething trouble, etchings on some blades are not perfect, but they are not terrible either, they are all identical in shape and size and after I found the correct way, it took me less than 5 minutes per blade.

Etching the numbers was a different kettle of fish after that, for the numbers are tiny, Glagolitic numbers can be quite funny-looking sometimes and I do not think I can cut stencils for them from 1 mm thick silicone sheet. I might try, but for now I reverted to my old method – scalpel and plastic adhesive tape.

Next time I will show you the actual knives that came out of this. I have to decide whether to make one post presenting them all, or scatter them over several days. I think I will do the latter. Either way, taking pictures will take some time too.

Behold: The Unbender!

As I wrote at the beginning of my making kitchen knives project (oh my, is it over a year already?), the steel bars often need straightening before a knife can be made out of them. The method I used then was not particularly time-consuming, but it was very annoying, with the screws constantly falling off to the ground and me cursing all the time. So I have decided to build a jig to help with the job. And here it is.

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This simple thingie took me a ridiculous amount of time to make. Like, three or four times more than it probably should. It might even have cost me more time to build it than I will ever save by using it, depending on how many knives I will make in the future.

The principle is simple, there are three rollers made from old piping and some ball bearings. Two are fixed to the base plate and one is on a plate sliding on two columns opposite them and center between them. A screw in the center can push the upper roller down between the two stationary ones and thus it can bend steel.

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The use is easy. Put the end of a flat bar between the rollers with the concave side down, tighten the central screw a bit and pull the steel back and forth end-to-end through the rollers (but careful not to pull it out completely, because that would mean starting over). Then check for straightness, eventually tighten the screw a fraction, pull, check again, rinse and repeat until the bar is straight.

It works actually very well. I have straightened all my bar stock in minutes and to a better degree than I was able to achieve previously. But still…

Well, hopefully, the finishing works on the forge will go a bit faster, because without the forge I can’t do squat.

Making Kitchen Knives – Interlude 3 – Knifemakers Do Not Make Mistakes…

…they just make smaller, thinner knives

When polishing the blades, I run with one of them accidentally across the edge of the platen. Literally, in a blink of an eye, I ground it paper-thin in a spot, almost through, and I overheated that tiny spot too.

Instead of simply tossing it, I have decided to re-grind it into a prototype of a small knife for peeling veggies and fruits, like garlic, onions, oranges and similar, and also for cutting small things like radishes. For these tasks, the universal kitchen knife that I was aiming for can be a bit unwieldy and I need to test various knife shapes and sizes anyways, so why waste a perfectly good hardened steel, amirite?

This is the resulting knife. The handle is from black elder (Sambucus nigra), artificially infused with silica. That makes the wood a bit harder and it also changes the color a bit in places, making the grain stand out a little more and with a greenish tint. It looks and works actually a bit like an untreated black locust – go figure.

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It is a nifty little blade that goes well in pair with the one I gave my mother two years ago. ~19 cm overall length, 9 cm blade. So far it works well for intended purposes, we will see if my main tester (my dad) is going to have some remarks or complaints. I think that with a sheath it would be a good pocket knife for mushroom hunting too.

Making Kitchen Knives – Part 17 – Watching the Paint dry

This step was a real bugger this time. Forming the handle before it is assembled onto the tang has its downsides, but it also has its upsides. And they seem to prevail, in comparison to the approach I took this time. It took me a lot of time to get all the handles into shape. Part of the problem was also that I have used woods of different properties and thus I had to adjust my approach several times – something that entirely defeated the purpose of saving time by working in bulk. But I got eventually to the stage when I could impregnate the handles with boat lacquer.

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For some of the woods on display here infusing them with drying oil or buffing with beeswax would be entirely sufficient. For some, it would be much, much better to stabilize them with resin beforehand. But the boat lacquer is the most durable and universally applicable finish I have right now, so I have used that. And to make the work more convenient, I have built myself a little stand to put the blades in to dry.

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Unfortunately, I am not done yet so I do not know how much time I have lost in this step. I only have enough data right now to know for sure that I have lost a lot, maybe even an hour per blade. The reasons for this are several.

First, this step was evaluated as “high hanging fruit” because I knew upfront that saving time here will be difficult. Lacquering is the most labor-intensive wood finish imaginable in this context.

Second, some of the savings in my previous step were not really time savings, it was merely that I have changed the order of operations this time and that moved some of the work time from that step into this one.

Third, I messed up, bigly, several times. I repeated steps tat needed not repeating and in the end, I had to redo the coating for four blades. This is why I do not have full data yet – right now, only 8 knives out of 12 are truly finished. But the purpose of learning was achieved, and I have definitively saved some overall time.

 

A Simple Knife Stand

The Covid-19 pandemic has prevented me from giving my brother the knife I made for his birthday, so I have used the time and I also made a simple stand for it. I have used black locust (Robinia pseudoacacia) wood from my firewood treasure trove. The wood is poisonous to ingest, but it won’t rub off on the stainless blade enough to be a problem.

It took me a bit longer time than it would had I been working with good planks because the cuttings were not perfectly square or flat and I had to do some fitting and gluing up in order to get big enough chunk for the base.

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After the glue-up when I started to square and polish the base I have realized that, quite coincidentally, I have glued it from two pieces that came from the same original plank, and that I have aligned the grain so that it makes a nice V-shape at the face.

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I have also found out that I will have to use another glue next time, since the one I am currently using turns black when gluing woods with high tannin-content, a problem that I noticed also when gluing leather with it. Which is a bummer, because it is very good, strong, and water-resistant glue that is really easy to work with. But the thin black line looks much worse on the picture than in reality.

The stand is covered with the same boat lacquer as the knife handle, but it is deliberately not polished and it has fewer layers since it should not get exposed to nearly as much water as the handle.

I will probably make some more knife stands/racks in the future

Making Kitchen Knives – Part 16 – Human-knife Interface

Last time I did this, I shaped the handle-scales first, then I fumed them wit ammonia and then I glued them onto the knives. This time I have changed the order of doing things, but time comparison should still be possible.

After taking the pieces of wood out of the solution I have left them dry. First for a few days outside, out of direct sunlight and out of the wind, with both end-grain ends covered with plastic to reduce cracking (still insufficient, next time I will have to try something more drastic). After they were dry and stink-free, I put them for a few days into the direct sunlight to dry even more, and then I left them to stabilize in the workshop for a few days. That way the wood should be neither too wet nor too dry and hopefully, it won’t change in size too much.

When I started to polish the pieces to sort them out properly – any markings were taken out by the solution – I could not find the oak pieces anywhere. So I took an offcut that was not in the solution and I polished that a bit and I realized that it is not, in fact, oak, but an especially dirty and grimy piece of black locust. I do not even remember where I got it and why I thought it is oak in the first place…

Anyhoo, after grinding all the pieces to flat and parallel, I drilled the holes for pins, cut all pieces to a rough shape on the bandsaw and I paired them up and I shaped and fully polished the forward-facing facets since those won’t be accessible once the scales are glued on. What I learned here was that I will need some finer scaled drill bits, since different woods react differently and when you drill with a 6 mm drill bit, the resulting hole can be anywhere between 5.5 and 6 mm. And trying to force the 6 mm brass pins through some pieces was a real pain in the nether regions. I have to drill the holes in wood ever so slightly bigger than the intended pin, but whilst 6.5 mm was fine for the softer woods it was almost too much for the harder ones.

The next step was glue-up.

To get as near perfect flat surfaces as I can, I have bought a spray-on glue and I used ti to attach a piece of coarse sandpaper to a granite tile. It worked really well, I have got a very nearly perfect match between the tangs and the scales on all twelve knives, the best result I have got yet for this type of handle construction. But I also managed to get a lot of glue on my hands and I lost the spray nozzle when wiping it off and it took two days before it resurfaced under the shop vacuum. So yeah, not my finest hour and the good came with some bad-ish.

During the glue-up, I have suffered from a common ailment –  the insufficient clamping power syndrome. I had to do it in two stages, gluing six blades in the evening and the remaining six in the morning next day, Which was not too much of a problem this time,  since I was tired and I would have to call it quits anyway, but I will probably need some more clamps or maybe even some thingamajigs for gluing the scales on the tangs more efficiently.

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And this is what I got in the end – a pile of roughly shaped handles attached to the finished blades.

During the subsequent grinding to shape with a 40 grit belt, I still could not do too much to evaluate the real effect of ammonia fuming on these woods, but I did get some inkling of what the results might be already. And let us say that for some of the woods I have preliminarily considered the results promising, for some surprising and for some completely “meh”. More about that when the knives are finished.

This whole step took me approximately 73 minutes per knife, and that is a significant improvement against last time – 38 minutes, 34%.

The last step is polishing the handles up to ~300 grit (already done) and putting on a protective coat of boat lacquer. That will take about a week, an hour or so a day. We shall see how that goes, but that part should be relatively free of any surprises.

Making Kitchen Knives – Part 15 – Tumble Time!

I was on and off working on this project in February. I have filled my tumbler with very fine sand (one that is used to fill in the spaces between concrete pavement bricks) and walnut shells and I polished the blades with increasing grit belts, then I stuck them into the tumbler for a day or two until I thought I can get the scratches all out after 12 hours evaluation.

It was still more time consuming than I would like to, mostly because many blades were ever so slightly bent, a problem that I really hope to solve with plate quenching in the future. On a bent blade, the concave part gets polished quickly, but the convex is a pain in the ass.

So I progressed slowly and at 150 grit I stopped, thinking that the fine sand can take the scratches out in time. It did, however, it took over a week in the tumbler, so next time I will go probably somewhere around 240 or perhaps even 320 grit before going to the tumbler. The blades did have a nice sand-blasted like look to them, so they were de-facto good to go functionally, but I thought they might be still improved by putting them in the tumbler some more. So I did, into a mixture of jeweler’s rouge (Fe2O3 powder) and crushed walnut shells. And I was right, they have now a very nice satin finish that I think is perfect for kitchen knives.

A mirror polish can be a bit sticky, so for kitchen knives, it is not the best option. I will see how sticky this polish is in a bit, but it looks good. Unfortunately, pictures do not give it justice, I won’t even try.

Time-wise, I have spent about 110 minutes per blade with this polishing process to achieve this result. So an improvement of 58%, but with a different look in the end.

Here is the blade line-up from worst to best:

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The first left blade has a slight crack on the edge. Not from the tumbler – that would be possible, but it did not happen – but from the one time where I forgot that the blades are drying on a rug and I took it to wipe my hands. All twelve fell to the floor and this one cracked near the edge and will have to be re-ground to a different shape – I do not know which yet. It was also one of the curly ones and that might have played a role too.

The second blade from the left would be perfectly OK if I did not mess it up. There is a place about 1/3 from the tip where I run accidentally not over the edge of the platen but over the corner. I nearly ground through the blade there, making an unseemly spot where it is paper-thin. I will probably prototype this to a much smaller blade, like a peeling knife. A lesson for the future.

The third and fourth are the remaining two of the curly-wavy blades. One will be re-shaped into a fish gutting/filleting knife for my uncle, one will remain an all-purpose kitchen knife, only with a slightly narrower blade than intended. It will be more similar to the knife I gave my mom and my brother.

The next five blades have a slight bend to the right side that I was unable to straighten out. They will be functional, but cutting straight will be a bit difficult, so not ideal for bigger things like cabbage, but still OK for carrots, leeks and onions, and sausages.

The last three are what I intended to achieve. 25% success rate – a disaster. But I am still learning, so hopefully next batch comes out better.

 

New Forge Build – Start

The lining inside my portable mini forge is starting to fall apart, and instead of repairing it I have decided to build a completely new one. I have observed a few problems with the old one, how to achieve the best circulation of the hot gasses etc, and I think I can do a better job at it now than I did then.

I started with a rummage around my junk-pile. I thought about the hows and whats and I selected a few pieces of steel v-profile, a few treaded rods with matching nuts & washers and a long piece of stainless chimney duct. Then I made a sketch (sorry for the grime, it occurred to me to make the pictures only after  I have done all the work).

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It is slightly bigger than the previous one, but it should still be easily portable. And the fireclay bricks fixed at the front and back will save me some time preparing for my work. I hope. I see no reason why it should not work as expected, but proof of the pudding is always in the eating. In my previous job, I have always reminded engineers that reality, not their expectations, is the ultimate arbiter of what works and how.

After I was done with the sketch, I started to make a list of parts. I have decided to not weld it together, but to use screws. Partly because my welding sucks big time, partly because the fireclay bricks are all miss-shapen and of different sizes and I wanted to have a bit of room to play and partly I reasoned that if it all goes south, I will be able to disassemble it easier. This has meant however that I had to ad a lot of nuts, screws, and washers and that has proved to be a bit of a problem. A lot of the M8 nuts and screws in my junkpile were rusty beyond rescue and I had trouble getting all I need.

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However, I have managed to get everything I need without having to go shopping. I cut the steel profiles to size, wire-brushed them, drilled holes, then filed some of the holes to an oval shape in order to be able to adjust the size of the holders for fireclay bricks and I assembled it to try it out. It seemed to work alright, so today I disassembled it all again. Then I degreased every profile thoroughly with acetone and I spray-painted them with silver stove paint (not the duct, since that is already stainless and the paint would probably not hold on it anyway). When the paint dried, I could finally assemble the whole thing together.

Here it is.

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Today I have made the mold for the inside – the actual chamber and the in- and outlet. This time with my old trusty method “just wing it, mate”. Tomorrow I hope to fill it with refractory cement.

I will post about how that went.

A Knife for my Brother

I did not manage to finish a knife for my brother’s 50 birthday last year, for I nearly hacked off my finger with a hatchet. So I am rectifying the issue this year.

This is the blade that was hardened when I was working on the rondel dagger. It is not a perfect blade, aesthetic-vise. I messed up the polish a few times and I had to eventually stop trying to correct it otherwise the knife would turn into a small razor. It is a good universal kitchen knife, very good cutter, I am just not happy with the surface finish. But it is either this or nothing and this year I want to give my brother a knife I know he wants. He is going to appreciate it even with the flaws.

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I tried to make up for the flaws with the handle, so I have used a piece of partially rotten lilac branch that I have harvested last fall. It is just stunningly beautiful wood and this is probably the prettiest knife handle I have made so far. The wood is rock-hard with tiny pores (lilac is one of those woods that can take 1000 grit polish without dirtying) and would probably hold up well even without the boat lacquer coating. But it was partially rotten, so the outlying regions were not only discolored, but also softer, so I soaked it in boat lacquer to stabilize it. With the coating, it should be near indestructible.

The lilac-colored heartwood will probably age into dark brown over the years, but it might take a really long time since the branch was already several years dead when I cut it off.

© Charly, all rights reserved. Click for full size.

© Charly, all rights reserved. Click for full size.

© Charly, all rights reserved. Click for full size.

A Hunting Knife – Auction for FTB Legal Defense Fund

You can still donate, the damage Richard Carrier has done with his petulance is not undone yet. I cannot afford to donate any meaningful cash right now since I have no income. But I can afford to donate a bit of time. So I am giving this knife in exchange for the highest donation. Details see further.

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Technically it is a hunting & fishing knife since my first customer specifically requested it for angling, but you need not be a hunter for having a use for it. I am regularly using a knife like this when collecting mushrooms or just walking in the forest when it might come handy. It would also be useful as an all-purpose knife for camping. The false edge is sharp, but not cutting sharp. The blade is signed and numbered “2” in Glagolitic script.

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I made a simple leather scabbard, this time symmetrical so the knife can be conveniently fastened on either left or right side since the preference of its future owner is unknown.

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The handguard/bolster has a few dark spots. These are inclusions in the used material (see further).

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The endcap is fastened over an ornate stainless steel washer into which is the end of the tang peened.

If you are interested, write your bid in comments or per e-mail to affinity (note, I might not be able to post your e-mailed bids in the comments next two days, there is a huge storm coming our way and I might experience blackout).

If you bid from outside of the European Single Market, please make sure that you are allowed to import such things and be prepared to pay for any import/customs fees, duties or other taxes as may be relevant in your region/country/state. I will pay for the postage.

The knife will be sent to you after submitting proof of the promised donation. If the highest bidder reneges on their promise, it will go to the next one in line. The start is 10$ (the cost of materials), the sky is the limit.

The auction will run for two weeks until February 23. 2019 and this post will be pinned to the top of the page until then.

More info below the fold.

[Read more…]

Making Kitchen Knives – Part 14 – Straightening Curls

Last time I was working on this project, I had some very bad results from quench. This week I have finally managed to test one idea of correcting the problem and maybe prevent it from ever happening again in the future. And I am glad to say that it did work. Not perfectly, but the new process is definitively worth to use instead of the old one.

Here is first the comparison of the three worst blades before and after. As you can see, there are still some curls in there, but they are noticeably less pronounced and one blade is almost completely straight. They will still come smaller than intended out of the polishing process, I will still have to remove some material from the edge until I get to the straight part, but I estimate it to be about 1/2-1/3 of what it was before. On the worst blade, the curls went about 10-15 mm from the edge towards the spine, whilst now it is about 3-5 mm. That is a significant improvement, and I think that had the blades been quenched from a straight form, they would never have curled in the first place.

As I alluded to previously, the process that I wanted to use for correcting the blades is called plate-quench. It cannot be used for simple carbon steels. Only so-called deep hardening steels can be thus quenched, and N690 is such steel, according to some articles I found on the internet. Nevertheless, it is better to not have the internet at all than to believe everything you can read on it – the manufacturer recommends oil quenching.

So I have tested the process first on one blade that I accidentally broke when correcting an ever so slight banana-bend. When the broken blade hardened properly – which I have confirmed not only by scratching with my gauges, but also by breaking off a tiny piece of it – I went on with the curly ones. On one of these, I confirmed the hardening too by breaking off a tiny piece of the tip, with the remaining two I was satisfied with the scratch test only.

For the plate-quench are used two flat plates from either alluminium or copper. These two metals have very high heat conductivity and thus can cool down some steels fast enough for them to turn into martensite. Luckily I got quite a few nice slabs of alluminium on hand. And because I wanted to make the process a bit faster (despite not making time-measurements this time), I have made a simple prototype quench-jig.

It consists of two identical pieces of alluminium with a small hinge, and locking pliers. The hot blade went out of the forge between the plates with the edge towards the hinge. Then it was firmly clamped by the pliers to hold it straight. When it stopped glowing near the tang – indicating a temperature well bellow 600 °C – I dunked the whole thing in a bucket of cold water just to be sure. And just as last time, because it costs nothing, I have put the blades into a freezer straightway for a few hours before tempering them. None of the three blades cracked.

Not an actual quench, staged photo – sometimes I miss having third hand greatly. © Charly, all rights reserved. Click for full

It worked reasonably well and quick. I will definitively improve it and build a proper jig when the weather is nicer and I do not freeze my nuts off in my workshop. I will add a more stable hinge(s) and maybe even screw one of the plates to the pliers.

Another advantage of this process is no burnt oil gunk on the blade, no flames and no stinking oil fumes.

Poor Man’s Belt Grinder – Mark 3

My belt grinder has served me well, and for a hobbyist, it would be probably good enough. But since I am inching my way towards knife making not being just a hobby, I needed some significant improvement on it. And an opportunity luckily arose.

One of the good things about my previous employer was that there was an internal process for employees to get obsolete materials and equipment either cheaply or completely cost-free. I have used this opportunity quite often and got a lot out of it – I am well stocked in graphite and alluminium, I got precise analytic scales completely for free, and one of the last things I have managed to get was a variable frequency drive.

I was not able to haggle this one down to zero, it was a bit pricey even though used, and I also had to pay a bit to a professional electrician to connect it for me. I could get a new one for a bit cheaper if I capped it at the 1,5 kW that my motor has (this one can handle 5,5 kW) and took the cheapest one there is, but it was still a good deal even if it was not exactly a bargain.

And it works like a charm, even when I am not able to use anything more than the manual mode yet. Finally, I have the ability to change the speed of the motor as I need it, I can even reverse the rotation. I have tested it already and it is exactly what I hoped for-  finally I can work wood without burning it and I can sharpen tools and have a bit more time before the edge starts overheating.

I hope it continues to work well – I have great plans for the future. Multiple grinding wheels, a polishing attachment and, maybe, even a lathe attachment. The belt grinder shall not rest!