i bought a bosch sander...

[inferno]

that i'm trying out as we speak. text between the pics!

basically i wanted to find a solution to grinding knives inside at my kitchen counter.

it a "flat sander" that takes velcro pads and also longer paper without velcro. it has adjustable speed. and a buolt in vacuum cleaner, that seems to work. feels solid. no toy.
bosch GSS 23 AE

so it has a stroke of 2,0mm, its one the biggest for this type of machine.

i'm making a knife right now and its a monosteel. high hardness blade. maybe 62-63hrc. 80crv2.
and i want o grind this indoors.

so this seemed like a fairly good idea.

i first mounted it upside down. fairly uncomplicated as you can all see. its basically a plate welded to a steel rod, then i strapped the grinder to the rod with a hose clamp. thats it. and its solid! also put some tape over the vent holes so it wont suck steel dust in there. its open, but it sucks from below now.

this is the knife. about 1,5mm to go there on the edge... a lot of steel there to get rid of.

i started out with the supplied sheets. 120grit red ones. they sucked ass. they had bite for about 20 seconds.
then i tried the yellow 80 grit pads that you can see in the pic. and they sucked just as much ass. 20-30 seconds and then they're done. these are wood pads. and these machines are "wood machines".

then i figured why not try out the manual paper we have at work and simply wrap it over the existing velcroed paper.
tried 40 and 80 grit.

they both sucked ass. wears out and lose bite in about 30 seconds or so. and i guess these are mixed wood/metal papers. quite low quality. würth brand.

there are very good papers for metals, like norton blaze, 3m trizact, 3m cubitron etc etc. but they dont make papers like this, in this size. so i would have to get long belts and cut up. and i will try this.

anyway i thought that soft backing cant be doing any good now. so made a steel plate from some scrap steel. that i will velcro to the velcro

today i got bosch "metal" paper in 60 grit to try out. could be good could be crap.
its a4 size. and it just happens that an a4 makes exactly 3 pads for this machine if you fasten them with the red rubber fasteners..

here you can see a 40 and an 80 grit paper that has lost bite. basically nothing happens with these papers after 20-30 seconds. they still feel aggressive and not worn at all. but no metal gets removed.

gonna try this one from work too. norton r929 belt i think. 50 grit.
i have also ordered some 3m cubitron 2 belts to try out. and if these dont work out well, then nothing will. then this whole method simply sucks ass.

it is what it is. wish me luck.

norton 50 grit. r929 (i think).

 

[Cloudsmoker]

Good luck, indeed. The steel backing plate should have helped a bit, too.

 

[inferno]

I think the real problem with all these pads, sheets and belts is that i cant fracture the grain to expose new sharp edges. so they just round over in like 30 seconds. and the steel backing plate will take care of that. maybe..

i also tried a 120 grit silicon carbide paper from an a4 paper, and it lasted about 30 seconds too. even though SiC is known to "fracture and expose new fresh grain" not on this soft backing i suppose.

things may very well change tomorrow when i install the metal plate but i kinda doubt it.

one think i dont doubt though is that getting good abrasives is the key here. getting stuff made for metal, high performance stuff. i also have a "floor sander", a small hand held belt grinder with 75x457mm belts - the hobby/sh1tty size. the pro size is 75x533mm (and defacto standard) and then the ultra pro 100x610mm, but also these machines are regarded as "wood machines", so there are no real good metal belts for these here.

would be nice to get the 75x457 going. but its the same as with tires, and shoes and speakers, its the last interface that really makes it or breaks it. and in this case its just sloppyness of the industry. i want good metal papers and belts in diy/"consumer maschine" sizes. it just dont seem to exist. not in europe at least.

 

[inferno]

i also got 40 and 80 grit papers for the 457mm machine today.

if none of the papers work out on the bosch i will sell it to a coworker most likely.

i might have to get a small, real but sh1tty belt grinder after all. i'm trying to avoid this.

 

[GoodMagic]

Rhynowet redline paper is great for hand sanding blades, might consider these?

 

[milkbaby]

Get a belt grinder or get ready to hand sand thru a bunch of sandpaper.

 

[gregfisk]

I hate to say it but I really think you need a belt grinder to grind steel. Even a small 1” x 30” will work and it won’t break the bank. Not sure about using it in the house though. Amazon has a lot of different size belts for steel grinding including 1” x 30”. I buy ceramic belts for my vintage 6”x 48” Delta belt sander. I wouldn’t recommend that for grinding knives but it sure works great for grinding on steel.

 

[Cloudsmoker]

So here's how I spent my COVID-19 vacation. Flipped a Rikon 1x30 with variable speed, glass platen, makeshift angle guide and retrofitted a buffing wheel in place of the disc grinder.
About $200 all-in. Fairly light duty, but helped me maintain prescribed social distancing.

 

[inferno]

i fitted the metal plate on my sander and ran the green norton belt. and it lasted for several minutes. but still not much steel got removed.

then i tried the bosch metal a4 sheets. and it also seems to last for a few minutes, but even then too little metal gets removed.

en funny thing though is that the regular yellow wood papers works ok-ish on soft steel. my metal plate was a bit oversized and there was no real problem taking down in size and chamfer the edges on it.

i will have to say this method is ineffective for grinding mono steel blades. its just too slow.

It might be good for wood (probably) and clad blades though. probably good enough for flattening bevels and different polishing jobs too.

It probably faster than stones though (and much less hand/arm fatigue). and you can do it indoors without dust getting everywhere unlike a belt grinder.

--------------

gonna whip out the lidl/parkside floor sander now and do the rest outside. i have new belts for it. 75x457mm lol. but it actually works quite well with fresh belts. if not in a hurry.

-------------

next machine on my to try list is a variable speed angle grinder. i see bosch has a 900w one that goes from 2,8-11k rpm
gws 9-125 s and since its not a 13-1700watter it has thin good grip for good control

 

[podzap]

Why would you possibly buy a corded angle grinder?

 

[BarryMM]

A belt grinder works best for removing lots of material. I use it for repairs and such. Being a hobby knife maker as well justifies having one

 

[podzap]

A belt grinder works best for removing lots of material. I use it for repairs and such. Being a hobby knife maker as well justifies having one

What the hell is a belt grinder? Never heard of such a device before.

 

[Matus]

I do not want to sound negative, but grindig steel in a kitchen is going to be a mess with no end. Either you get tools that can’t really remo steel (your current solution), or you get a belt grinder of some sort (yes, 1x30” can actually be used to make knives) and you will have steel dust in every tee cup (and later also other rooms). I have invested 1000€ just in dust reduction in our basement, and it is still far from perfect (but good enough for a basement).

I do not know how much room you have, but building a plexiglass enclosure where you put your grinder and using wet grinding for steel and using a decent dust extraction when grinding non metals might be a solution, but still the rest of the room will be just a workshop, not a normal room.

 

[inferno]

i went out with the lidl grinder. used up 4 belts. its nice to see when something is actually happening..

 

[inferno]

Why would you possibly buy a corded angle grinder?

because its very versatile. you can do almost everything with them. and if you have a light, slender one with adjustable rpm you can do even more.

and a cordless one isn't really anything i want. we have several at work and they are all crap. cant cut steel quickly with them because they are too weak and the battery last for like 5 minutes. also very unbalanced machines with a heavy battery on the bottom. the exact opposite of the slender 7-900w corded ones. thats why. more questions?

 

[ma_sha1]

I used a mouse sander for thinning, faster than stone for sure but slow.

I have a 1x30 sander, this things is too fast, narrow belt hard to control, very unforgiving! looking to upgrade to 2x42 possibly.

I just got a 3x21 sander, it’s faster than mouse sander for sure, but much slower than, still experimenting but looks promising as a thinning machine, but too slow for re-profiling. still need the 1x30 for reprofiling.

 

[BarryMM]

What the hell is a belt grinder? Never heard of such a device before.

https://www.tomtek.eu/product/professional-belt-grinder/

 

[Matus]

I have seen that one elsewhere, unless I am mistaken it is being build in Polen and marketed via different shops.

 

[Matus]

You can find a list of grinders available in Europe here:
https://matuskalisky.blogspot.com/p/supplies-services-in-deeu.html?m=1

 

[inferno]

the little grinder that could..

tried out bosch X440, 40 and 60 grit papers this time for the lidl grinder. i'm actually quite happy with the grinder. i think it was 30-35€ and it works. 170-250m/s belt speed.
i was at the store this friday to get paper and checked out all similar brand name grinders. up to maybe 100-120€ its all the same crap as this one. in different colors. mine is made to run upside down, it even comes with clamps to clamp it to a board.


bosch has a bigger one though, the GBS 75 AE, but its 300€ and it looked a lot better than mine. I will probably get one of those when mine dies.

i think it took me about 1h to grind this one out. the belts seemed to have good bite for about 2 minutes and then acceptable bite for maybe 10.

 

[BarryMM]

I bought mine from https://www.smederijatelieralkmaar.nl Highly recommended.

 

[inferno]

i put the 60 grit belt sanded bladed on the bosch. first a worn out 60 grit "metal" for about 3 minutes then a würth brand SiC paper 120 grit. for about 5 minutes.
the SiC lasted for about 30 seconds or so lol. this machine is so destructive. god damn.

instant stonewash finish!!

 

[BarryMM]

3m cubitron belts are, in my opinion, excellent belts for large metal removal. 36, 80, 150 grit. The higher the grit, the less heat you generate. That is really important if grinding on hardened steel. If it get's to hot you will ruin the heat treatment. Keep a bucket of water to cool between grinding passes if needed.

 

[inferno]

so i got hold of 3m purple cubitron 2 sheets in a4 size. they cost about 1€ a pop. and they are marketed for wood, primarily i guess. they are in the consumer product department on 3m's site, under "advanced abrasives".

the bosch metal papers (the red sheet above) has maybe good bite for about 1 minute, then semi good for another minute and then mediocre for about 10m (but much much better than the other papers including the würth SiC sheets, maybe 10x better overall.)

but the purple cubitron 2 sheets has good bite for at least 10 minutes. i basically gave up after 10 minutes. because i was done with what i wanted to do. and it still had better bite than the bosch metal when new.
I'm guessing one could go about 15-20 minutes on these papers before they turn ineffective. these papers remove a lot of material very fast.

i can see grains of abrasive has gotten dislodged from the cubitron paper but it still keeps on cutting almost like new. i think i have lost about 10-15% grains in 10 minutes. they get torn off. but the ones that stays put do their job. and in 10 minutes i think i have lost about 50% speed compared to a new cubitron paper (but its still faster than a brand new SiC/bosch metal/the other crap papers when new).

the pink spots on the paper is dislodged grains.

this is the finish off the 60 grit paper with the bosch excentric sander.

 

[kbright]

I like the upswept tip on your blade. We used to call these Persian style.

On a belt grinder, the ceramic belts do best at high speeds and heavy pressure.