Belt sanding tips

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ian

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Trizat grit table

@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 :p
Thanks, I'll try them at some point, although I've got a lot of belts right now. Still haven't been able to get the slack belt to really contact the middle of the blade, even with upping the tension. (Thanks @inferno for helping me find the tension control. Doh. 😂)

On the upside, I was able to soak and stretch the fine scotchbrite so that it works on this grinder. Tempted to try the medium or coarse and stretch them as well, but @Matus's word of caution probably means I won't.
 

ian

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Yea, i have used about 1,5 of each a100 and a45 for the complete massdrop order of 30 knives. Insane value.
Is that 1,5 like between 1 and 2? Woah.
 
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stringer

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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.
It kind of depends on what shows up at the pawn shop.
 

inferno

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good idea! mine was 30 or 40€ so i'm happy with that. i have so far made about 5-6 knives and a sword with it. so i got my moneys worth i think.

stinger make sure to lube/oil whatever bearing there is then its good for some action. tear it down.
 

stringer

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good idea! mine was 30 or 40€ so i'm happy with that. i have so far made about 5-6 knives and a sword with it. so i got my moneys worth i think.

stinger make sure to lube/oil whatever bearing there is then its good for some action. tear it down.
Alright I will do that. I also have told a couple of places to call me when they get a nice commercial grade one that hasn't been used much. And when I buy it I will pick out an angle grinder to go with it. Got any tips for what to look for with an angle grinder?
 

inferno

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Alright I will do that. I also have told a couple of places to call me when they get a nice commercial grade one that hasn't been used much. And when I buy it I will pick out an angle grinder to go with it. Got any tips for what to look for with an angle grinder?
yeah get the one with the thinnest shaft/handle. those are usually the low power ones like 600w. much easier to control and handle. the big power ones are very heavy and bulky and they are hard to control.
 

ian

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Update on putting belt finishes on knives people give me to sharpen: still haven't really managed to get it work.

Slack belts: My problem is that for knives with with any small concavities, a slack belt doesn't work, and even when the grind is convex but fairly flat, I'm not able to get enough pressure in the middle of the blade using a slack belt. I think this may be because I can't tighten my belt enough without overloading the motor, but I don't know what's realistic to expect since it's my first machine.

Soft platen: I tried mounting various things on the platen to have something to push against, but the back of the belt just wore through them almost immediately. Plus, with any pressure, the grabbiness of the soft backing increased friction, and the belt wouldn't even run.

Scotchbrite: a belt that itself has give like Scotchbrite worked the best, but I only have ultrafine right now and it wouldn't take out any lower grit scratches. It's also a huge pain to get it to fit on my machine, and to have the motor actually run with it on. Lots of stretching is required. I might try buying the coarse Scotchbrite belts, but am still worried given Matus's experience.

(FYI, @Runner_up)
 

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Are you just grinding on the blade face only? Are you grinding with blade edge facing up, or down? If there's to much space between platen and belt, I would find a piece of tempered glass or some tool steel and jb weld it in place.

One of the major drawbacks to a 1x30 with a sloppy platen/ tool rest is the edge of the belt digging into the metal or wood. Holding and moving the knife and moving it across while keeping it perfectly straight can be a challenge.
 
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ian

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Are you just grinding on the blade face only? Are you grinding with blade edge facing up, or down? If there's to much space between platen and belt, I would find a piece of tempered glass or some tool steel and jb weld it in place.

One of the major drawbacks to a 1x30 with a sloppy platen/ tool rest is the edge of the belt digging into the metal or wood. Holding and moving the knife and moving it across while keeping it perfectly straight can be a challenge.
I can adjust the platen depth, so I don’t think that’s really the problem. I’m grinding on the blade face. (By “only”, do you mean to ask if I’m hitting the edge?) Edge faces down.

I agree about the 1x30 difficulties.
 

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Update on putting belt finishes on knives people give me to sharpen: still haven't really managed to get it work.

Slack belts: My problem is that for knives with with any small concavities, a slack belt doesn't work, and even when the grind is convex but fairly flat, I'm not able to get enough pressure in the middle of the blade using a slack belt. I think this may be because I can't tighten my belt enough without overloading the motor, but I don't know what's realistic to expect since it's my first machine.

Soft platen: I tried mounting various things on the platen to have something to push against, but the back of the belt just wore through them almost immediately. Plus, with any pressure, the grabbiness of the soft backing increased friction, and the belt wouldn't even run.

Scotchbrite: a belt that itself has give like Scotchbrite worked the best, but I only have ultrafine right now and it wouldn't take out any lower grit scratches. It's also a huge pain to get it to fit on my machine, and to have the motor actually run with it on. Lots of stretching is required. I might try buying the coarse Scotchbrite belts, but am still worried given Matus's experience.

(FYI, @Runner_up)
Your tension isn't adjustable enough and your rpms are too high. And trying to feed that little machine less power to slow it down would probably exacerbate your stalling issues.

You could try silicone grease/ lubricant of some sort on whatever you put over the platen to reduce friction.
 

ian

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You could try silicone grease/ lubricant of some sort on whatever you put over the platen to reduce friction.
Guess that's a decent idea, but I worry that then the grease is going to transfer to the back of the belt and make it just slip over the wheels instead of be driven by them. Anyway, that's why I haven't tried yet. Maybe I should.
 

stringer

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Guess that's a decent idea, but I worry that then the grease is going to transfer to the back of the belt and make it just slip over the wheels instead of be driven by them. Anyway, that's why I haven't tried yet. Maybe I should.
There are a bunch of varieties. Some harden up more like a caulk than a grease.
 

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Also, I find it more successful/easy to control if you face the blade up/against the belt direction. Just be careful.
 
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Bensbites

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@ian, I was told Brian Housewert (a grinder building guy) to sandwich a piece of leather between the platen and the platen mounting bracket to make a soft platen. This is easier on some grinders than others.
 
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tostadas

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I've used Delrin (acetal) plastic parts in applications where I want to minimize friction, like inside of paintball guns. I don't know how it would fare as a platten for a grinder, but perhaps look into trying out a flat Delrin sheet?

 
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ian

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@ian, I was told Brian Housewert (a grinder building guy) to sandwich a piece of leather between the platen and the platen mounting bracket to make a soft platen. This is easier on some grinders than others.
?, like behind the platen? How does that make it softer? Maybe I’m misinterpreting
 

inferno

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when i was sanding doors and other crap all day long we had these thin black porous plates, maybe 3-4mm thick, placed under the belts. they felt very slippery. these lasted for years. i think this i a very common an inexpensive product. might be a carbon/graphite based judging by the color.

i know other have tried glass and ceramics for the back plate. its very easy to shape glass with diamond plates.

but imo ian, you either go all in on modding that **** grinder.

or get a floor sander. its cheap and it works.
 

inferno

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if i was getting short belt grinder i would get this one. it seem this is the only serious one.
metabo bs175 500w. not much juice but probably enough though.
 

inferno

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ian i see your grinder is only 1/3 hp. thats about 250w. and i'm guessing you might only get half or 2/3 of that to the belt. it might be too weak for what you want to do?

my 600w lidl grinder gets about 400w to the belt and even that one bogs down when grinding steel.
 
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Luftmensch

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I went with a cheapo 100 x 914mm (4x36) - the inverted belt-sander style. It is great at hogging away material with low grit belts (~60). As others have recommended, Norton Blaze cuts aggressively which is useful on a weak machine with lots of slop. Definitely use quality belts... the cheap ones have a terrible working life.... if things are going slow, check your belt and make sure you haven't worn it out!

This is what I did to get a little better performance out of mine:
  • Dismantled the machine and reassembled it with more attention to spacing out the rollers for tension.
  • Added gaffer tape to the centre 50% of the rollers
    • to add a little further tension
    • to add more grip (rather than the slippy aluminium roller)
    • to add more exaggerated tracking
Given it is cheap the following are unsurprising:
  • the machine gets hot after a while and loses power
  • I can cause the belt to slip if I put too much pressure on the belt
  • I can cause the machine to stall if it is running hot and I use too much pressure
    • This said; too much pressure is too much pressure on a low grit belt - particularly if working on hardened steel (heat build up)
  • No speed control
    • this is fine with low grit belts that are good at dissipating heat
    • for 'higher' grits (~240) it is easy to accumulate a lot of heat quickly
  • The large 100m (4") width can be difficult to work with (shouldnt be a problem for you):
    • belts with wonky joints or crud accumulated in one spot can cause localised 'over grind'

As for finishing... I mostly use the machine for thinning at lower grits. I 'finish' at 240 grit before moving to stones. The wide 4" table is a blessing and a curse. It smooths out motions which is good for blending but it is bad for focusing on small areas. Given the width, you really have to focus on even pressure across the table (not too heavy on either the left or the right). Light pressure and keep moving!!

Another downside of these cheap machines is the belt length... 30" isn't very long. With a bad belt, I can't imagine a 400 grit would last for more than a handful of passes on my grinder. It is possible the speed isn't even compatible with a good belt at that grit! I don't know! That hunch has prevented me from trying!
 
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Taz575

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Some guys use very hard felt (McMaster-Carr) that has some give to it. I want to try this, but I have only 1 platen at the moment and was going to add pyroceream glass to it for flat grinding.
 

rogue108

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Everyone here is more qualified than I am in regards grinding and finishing but here is one tip that's helped me. I turned my 1x30 on it's back to make it horizontal than vertical. The base of the grinder faces away from me and the top guide wheel is closest to me. The platen is such a small area to work with I couldn't get used it vertically. On it's back it mimicked sharpening on stones and was for me easier control. Also when it's setup this way the belt spins away from you and prevents a knife from being chucked at your face if it gets loose. It really wouldn't work if it was spinning the other way. You have to jury rig a way to keep the machine from vibrating a way when it's setup this way.

I tried using a piece of Delrin between the platen and the belt get a better backing for sharpening purposes. It helped but the speed of the belt wears it away quickly. I used the slack section between the platen and the top guide wheel for finishing purposes. I never got a good, even finish off the 1x30 but didn't try hard either.

I found the largest assortment of 1x30 belts at Trugrit abrasives. They have AO, SiC, zirconia, diamond, Trizact, Gator, Blaze, leather, Scotchbrite in all different grits. Belts I never thought they bother making for a 1x30

Hope this helps a little.
 
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