Belt sanding tips

[ian]

I've been playing around with my newish belt sander a lot recently and thought it would be nice to have a thread for questions and comments about their use in knife making/modifying.

Most recently, I've been trying to get a decent finish on a couple knives using my cheap Harbor Freight 1x30. So far, it seems like with a pretty slack belt I can't really get the belt to do much, and what grinding there is is mostly done toward the spine and edge of the knife (depending on the angle I'm holding it) rather than in the middle. I have better luck using a platen (or whatever you call the cheap little bit of metal that comes with my grinder) and starting with the belt a few mm away from it, so that I push it into the platen. Maybe because there's still some give in the belt, the finish seems to come out ok --- it's not like it's just removing metal right at the contact point with the platen. But it's kind of hard to hit every part of the knife this way, since the polishing is kind of localized. Anyway, it's taking much longer than I thought it would to get a good finish. I'm mostly using 220 and 400 grit aluminum oxide belts at the moment, with aspirations to continue to higher grits. Even with the 220, it's taking a long while to remove the scratches from the Sigma 240 stone I used on the blade. (Yes that stone makes deep scratches, but still.) Anyone have any tips?

 

[inferno]

i mostly use my lidl floor grinder for making knives and i try to pretty much remove as much metal as possible with it.
i often work on hardened and tempered carbon blades (low temper).

so to not over heat these, i locate the knife over the belt where i want to start.
quickly push blade down on the belt then kinda reverse for few cm, to my real starting point,
push down to my working pressure (which is high), then do one lap/cycle from heal to tip. thickness of the steel determines how log this takes. usually around 2-3 seconds for a 200mm blade or so. i cool my blades after each cycle.

my philosophy on grinders is this: either you grind or you dont. and when you grind, you do it as determined and focused as possible, you gotta show the machine whos the boss. i've been working with different knid of industrial grinders since i was 14 or so. and most of the time you simply can f around with these or you will ruin the thing you are grinding. so you cant usually just "grind a little" you either do it properly or you dont do it.

now finishing things is a different matter and you will have to experiment. btw 220 and 400 might be coarse with stones but on grinders this is "fine"/slow.

i'm running 40/60/80/100 belts for my lidl grinder.

also i try to do everything on a tight belt with backing platen. if you want convexity, spin the blade around. you will have to experiment.

one thing i have learned though, and this is the most important thing of them all. position the grinder platen or whatever you have in the most ergonomic position so you can easily see what going on and you can move the knife around easily.

i basically have my grinder set up as a motorized stone just below heart level. total control, easy to see. ergo to use.

good luck.

edit: here is my beauty

 

[ian]

Nice. Part of my frustration is that I don't think I have control over the tension of the belt with the cheapo belt sander I have.

 

[inferno]

and as opposed to common belief (maybe not so much on this forum though) you can make a knife from scratch with your grinder ian. you just need to get some 40/60 grit belts to start with. try to make a good solid platen to work off. one that wont wear away in 3 hours. if i can make knives with my **** grinder so can anyone with any grinder imo!

 

[inferno]

Nice. Part of my frustration is that I don't think I have control over the tension of the belt with the cheapo belt sander I have.

can you post a pic of it?

you can either mod it so you can tension stuff properly or simply put a new platen on there and space it outwards so the belt gets tensioned by the plate.

 

[ian]

and as opposed to common belief (maybe not so much on this forum though) you can make a knife from scratch with your grinder ian. you just need to get some 40/60 grit belts to start with. try to make a good solid platen to work off. one that wont wear away in 3 hours. if i can make knives with my **** grinder so can anyone with any grinder imo!

Yea, I totally believe that. The 60 grit belts I have are nice and aggressive.

space it outwards so the belt gets tensioned by the plate.

That's a good point. There's not a ton of slack belt space left when the platen's on there though. I also kinda wish I could get *more* slack, because a thick surface conditioning belt I bought won't even fit on it. It's this one:

https://www.amazon.com/Belt-Sander-...prefix=belt+sander+1x30+harbo,aps,150&sr=8-19
I think. It was cheaper when I bought it.

 

[inferno]

well you need to find a place where you can tension the belt.

whats that thing with a knob in the back?

 

[inferno]

maybe put tape on the wheels to increase diameter?

 

[ian]

I haven’t really tried tensioning it, it just wasn’t obvious that I could. I should go look at the machine and figure out what’s possible before replying more about that.

 

[stringer]

I have a Rikon 1x30. I have mainly used it to thin cheap stainless and vintage carbon. I also have had good luck microbeveling edges with a leather belt and compound. I have finally bought a house so I will be able to do more and I plan on building an @inferno inverted floor sander setup soon. First order of business for my workshop though was building a workbench. Fifth coat of shellac. A couple more coats and then I'm going to wax it and it's done. I'm pretty happy how it came out considering the sorry heap of twisted rotten pallet 2x4s it is made of.

 

[RDalman]

For finishing slack belt is a good idea like you started. But you need kindof a superlight convex base from fresh 60 grit already and then follow through the grits, and only use brand new fresh belts for this. So if you can get a little more tension on the belt, try again... A ~240 grit slackbelt finish is indeed acceptable looking most of the time. Even better if you can follow it up with some scotchbrite or buffing. My final belt is trizact (gator) A45 which is ~400 grit, but followed with buffing work.

 

[branwell]

For an even machine finish, think of it like hand sanding. You do the bulk of your sanding with a hard backing and move to a slightly softer backing when you finish. In this case, using 3M, you can temporarily attach felt or leather to the platen for similar effect.

The trick is the right about of "give" for the shape you are finishing. If its a flat grind, you want very little "give". If its a convex grind, a little more "give", so use more or less felt. Try one thin layer. If that is not enough, try two etc.

Tip: You likely don't want to convex into the edge so hold the edge inline with the top of your felt layer will reduce belt pressure at the edge.

 

[branwell]

My final belt is trizact (gator) A45 which is ~400 grit, but followed with buffing work.

If you haven't, try a trizact finish with a soft platen. Pretty nice for a machine finish.

 

[branwell]

.

 

[ian]

For an even machine finish, think of it like hand sanding. You do the bulk of your sanding with a hard backing and move to a slightly softer backing when you finish. In this case, using 3M, you can temporarily attach felt or leather to the platen for similar effect.

The trick is the right about of "give" for the shape you are finishing. If its a flat grind, you want very little "give". If its a convex grind, a little more "give", so use more or less felt. Try one thin layer. If that is not enough, try two etc.

Tip: You likely don't want to convex into the edge so hold the edge inline with the top of your felt layer will reduce belt pressure at the edge.

Ah, so people use soft cushions on their platens? I wasn’t sure that would work because of the friction.

 

[tostadas]

Comparing belt grits to Jstone grits, I feel like there is at least a 3-4x difference. ie. 80grit belt feels like at least 240grit stone.

 

[RDalman]

If you haven't, try a trizact finish with a soft platen. Pretty nice for a machine finish.

I grind on rubber wheel, thanks for the thought though

 

[branwell]

Ah, so people use soft cushions on their platens? I wasn’t sure that would work because of the friction.

Friction does play a roll but not as bad as one would think. That said, I do run stuff like felt and leather on a speed controlled grinder running at half speed or lower. Best to try it and see. Worst thing that will happen is it will wear out sooner than later, but when it comes to machine finishes, soft is good

 

[ian]

Friction does play a roll but not as bad as one would think. That said, I do run stuff like felt and leather on a speed controlled grinder running at half speed or lower. Best to try it and see. Worst thing that will happen is it will wear out sooner than later, but when it comes to machine finishes, soft is good

Hmm. Mine isn't speed controlled. I almost think a felt backing behind the belt would be a fire hazard. Food for thought.

 

[RDalman]

Hmm. Mine isn't speed controlled. I almost think a felt backing behind the belt would be a fire hazard. Food for thought.

Yes those little bastards can run like crazy. Is it possible to find scotchbrite or trizact belts for them? Scotchbrite could be useful for your sharpening stuff pulling like a quick buff on blades.

 

[Illyria]

I made a few knives on my 1x30 harbor freight sander before I got my 2x72 variable speed one.

The tension of the belts is really random between brands. Adding some tape to the wheels can work.

Finish on brand new belts. With how quick the speed is and how little contact you can get on a 1 inch platen, you need to move really quickly.

Don't go higher than like 300-400 grit. The knives will over heat really quickly due to the speed of the 1x30.

 

[ian]

Yes those little bastards can run like crazy. Is it possible to find scotchbrite or trizact belts for them? Scotchbrite could be useful for your sharpening stuff pulling like a quick buff on blades.

I bought something like a scotchbrite, but it’s actually too tight and the motor can’t turn it. Might try soaking and stretching it.

 

[Bensbites]

I have a rikon 1x30, I use it for western handles due to the dust collection. I tried to grind blades and it was sssllooww!!! My platen aka little peice of bent metal is adjustable forward /back. You can also epoxy some steel to your platen to bring it forward.

 

[inferno]

For finishing slack belt is a good idea like you started. But you need kindof a superlight convex base from fresh 60 grit already and then follow through the grits, and only use brand new fresh belts for this. So if you can get a little more tension on the belt, try again... A ~240 grit slackbelt finish is indeed acceptable looking most of the time. Even better if you can follow it up with some scotchbrite or buffing. My final belt is trizact (gator) A45 which is ~400 grit, but followed with buffing work.

how does the trizact naming scheme go vs grit? is it in microns?

 

[Matus]

Trizat grit table
https://picard-kg.de/wp-content/uploads/englisch-tabelle.png
@ian - get some trizat gator belts - you can find them at supegrit.com (that is where I bought mine when I started with 1x30") and add a few Norton Blaze in 60 and 120 grits. The Trizact will give you nicer finish than AO I think. You can also try to add the "fine" scotchbrite belts for final finishing. Just don't get medium or coarse - the give so much resistance, that my 1x30" (250W) was not able to spin them

 

[Bensbites]

Trizat grit table
https://picard-kg.de/wp-content/uploads/englisch-tabelle.png
@ian - get some trizat gator belts - you can find them at supegrit.com (that is where I bought mine when I started with 1x30") and add a few Norton Blaze in 60 and 120 grits. The Trizact will give you nicer finish than AO I think. You can also try to add the "fine" scotchbrite belts for final finishing. Just don't get medium or coarse - the give so much resistance, that my 1x30" (250W) was not able to spin them

I think trizact is AO, just a specific type made by 3M. I plan on getting done soon.
I have recently been getting good results by rubbing my scotch bright with brown or white rubbing compound.
I know people who say they get good results by covering scotchbright belts with wd40.

 

[inferno]

I have a Rikon 1x30. I have mainly used it to thin cheap stainless and vintage carbon. I also have had good luck microbeveling edges with a leather belt and compound. I have finally bought a house so I will be able to do more and I plan on building an @inferno inverted floor sander setup soon. First order of business for my workshop though was building a workbench. Fifth coat of shellac. A couple more coats and then I'm going to wax it and it's done. I'm pretty happy how it came out considering the sorry heap of twisted rotten pallet 2x4s it is made of.

View attachment 115675

yeah try the floor sander option. i like mine on the pedestal i built. its about as optimal in position as i can get a grinder imo.

if you're only making a few knives a year its fast enough. if you intend to use this system for a long time i suggest going with a known brand that sells spares for the machines. so you can replace bearings/rollers/platens etc or you can simply make them.

i'm thinking about getting this blue bosch one below when my lidl grinder dies. just because i will be able to get spares for it all over the world. also comes with spare wear plates from the start! also if you are in the US i think 3M sell cubitrons in this size.
the GBS 75 AE

 

[inferno]

Trizat grit table
https://picard-kg.de/wp-content/uploads/englisch-tabelle.png

appears to be microns.

 

[inferno]

I think trizact is AO, just a specific type made by 3M. I plan on getting done soon.
I have recently been getting good results by rubbing my scotch bright with brown or white rubbing compound.
I know people who say they get good results by covering scotchbright belts with wd40.

iirc the trizact is AO that they shaped in to pyramids or something and the abrasive itself might be "ceramic" so when it breaks down it always exposes a sharp fresh edge or something. it was a long time i read about these. but i can confirm that whatever mojo magic they are doing with the cubitrons, it works!

 

[Matus]

Trizact gagtor behave differently in use than tradditional AO. They also last very long and what I totally love is that over their lifetime their performance does not change.