How long does sandpaper last?

ncrockclimb

ncrockclimb

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I have been working on my sharpening skills with sandpaper. My best results have come by using spray adhesive to mount 3M wet dry paper directly on balsa wood. However, I am not sure how long the sandpaper will last and if / how I should clean it. Any feedback and advice on sandpaper would be greatly appreciated.

Also, what grit should I expect to be able to slice though thin magazine paper? At 400 grit the edge catches and rips the paper. After stropping (on Flexcut or Stropman black & white) I can get mostly clean slices. Is this normal?
 
I've been using the same sheets for a few months now and still getting good results...I sharpen most over a mouse pad but my non convex knives like scandis I set the paper ontop of glass. I go up to 2k and get a slicing free hanging phonebook paper edge. I can easily cut copy paper at 600 for my coarser edges.

I just use water to clean off residue after about 5 sharpening sessions.
 
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ncrockclimb said:
I have been working on my sharpening skills with sandpaper. My best results have come by using spray adhesive to mount 3M wet dry paper directly on balsa wood. However, I am not sure how long the sandpaper will last and if / how I should clean it. Any feedback and advice on sandpaper would be greatly appreciated.
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Are you using one inch wide balsa? Thats a tip, take 10-11 inch sheet of sandpaper, cut into 1 inch strips, glue to 1inch wide piece of wood with rounded edges (important for flatness)

To clean you can use soapy water, Toothbrush also helps,
or you can use any kind of vegetable oil as lube while you sharpen and cleaner...
thats the benefit of wet dry :)

It should last a 60-200 sharpening sessions easy ... even longer if you use something coarser first (80 grit)

ncrockclimb said:
Also, what grit should I expect to be able to slice though thin magazine paper? At 400 grit the edge catches and rips the paper. After stropping (on Flexcut or Stropman black & white) I can get mostly clean slices. Is this normal?
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Yes, this sounds normal,
you raised a burr on the sandpaper then you got rid of it ( cracked + polished ) on your strop
its very easy to raise a burr with the sandpaper
 
Easiest way to clean is with an eraser or synthetic cork. They can last a long time if you keep it clean as you go. Is important to use in a progression, leaning on it to grind faster will kill it pretty quickly.
 
Sandpaper is a one use item in most cases, it will still "work" for many uses after but the aggressiveness and scratch pattern will be constantly changing. The Silicon Carbide abrasive breaks down quickly which is half the reason it works so well but, this also means it doesn't work the same as the first time it was used.
 
Jason B. said:
Sandpaper is a one use item in most cases, it will still "work" for many uses after but the aggressiveness and scratch pattern will be constantly changing. The Silicon Carbide abrasive breaks down quickly which is half the reason it works so well but, this also means it doesn't work the same as the first time it was used.
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That's bs, sand paper isn't a "one use item". Granted it does wear with use but not once..I have sand paper sheets that have been used numerous times for months and it'll still get my knives hair popping sharp.
 
I replace them when cleaning them doesn't restore rapid grinding. They lose the initial good bite and settle down to a pretty constant level for the duration. They will reach a point when the abrasive is all used up and just becomes glazed. Plugging them will trash em fast too, but a few drops of oil can often bring them back for a few more uses. I have sheets that have lasted for a long time - most of mine get replaced from being nicked, not worn out.
 
ncrockclimb said:
I have been working on my sharpening skills with sandpaper. My best results have come by using spray adhesive to mount 3M wet dry paper directly on balsa wood. However, I am not sure how long the sandpaper will last and if / how I should clean it. Any feedback and advice on sandpaper would be greatly appreciated.

Also, what grit should I expect to be able to slice though thin magazine paper? At 400 grit the edge catches and rips the paper. After stropping (on Flexcut or Stropman black & white) I can get mostly clean slices. Is this normal?
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Throwing in my 2 cents' worth:

How long it lasts depends a lot on what you expect it to keep doing. At the most basic level of functionality, it'll keep abrading for a long while. But at coarser grits of the SiC wet/dry (~ 400 or lower), it doesn't take long for it's coarseness/heavy-grinding characteristic to change. This is more noticeable if you are doing heavy grinding with it, as it'll slow down somewhat as the SiC grit breaks down. But, as Martin (HeavyHanded) mentioned, it usually sort of plateaus out a bit, settling into a finer, but still useful behavior, depending on what you use it for. At finer grits of 600+, I usually LIKE the fact that it gets finer, as it then gets better at refining/polishing edges, and gentler as well (this means burrs created tend to be smaller & finer). 1000-2000-grit paper will eventually make a great polishing strop, for example, as it gets 'finer' with use. In all cases, keeping it clean (unclogged) makes a big difference as you work. I've had very good results in just wiping down dry paper with a microfiber towel, such as the yellow ones often used for automotive polishing/buffing tasks; it does a great job lifting the swarf off the paper, and I also use them on my other hones, when used dry.

Slicing magazine/phonebook/newsprint paper can be done at most any grit, from 220/320 and up. Most of that just comes down to fully apexing and cleaning up or minimizing burrs (snagging & catching in the paper is almost always due to burrs). Reducing the pressure used with the sandpaper, at any grit stage, will do the most for minimizing burrs and also makes it easier to clean them up. You've already noticed the slicing gets better after a few passes on your strop, which confirms what's happening as the burrs are reduced. More practice and development of your 'touch' on the sandpaper (and any other tool) will eventually make it a lot easier to get clean-slicing edges with minimal stropping needed.


David
 
Bobby3326 said:
That's bs, sand paper isn't a "one use item". Granted it does wear with use but not once..I have sand paper sheets that have been used numerous times for months and it'll still get my knives hair popping sharp.
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You should try reading that again, that way your response might actually make sense.
 
Jason B. said:
You should try reading that again, that way your response might actually make sense.
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I've reprofiled several knives with a single sheet without seeing any drastic change in grinding performance from one to the next. The wear in the sand paper has been very minimum and hardly should be described as a one time use. That's like saying I need to use a new belt on the work sharp everytime I use it.
 
There are way to many variables involved to know how long sandpaper will last. A sheet of sandpaper may last months if you are only using it to do touch ups on a small 1095 blade but if you are reprofiling S110V that same sheet of sandpaper may only last an hour.
 
Jason B. said:
Sandpaper is a one use item in most cases, it will still "work" for many uses after but the aggressiveness and scratch pattern will be constantly changing. The Silicon Carbide abrasive breaks down quickly which is half the reason it works so well but, this also means it doesn't work the same as the first time it was used.
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Why is it important that sandpaper maintain its aggressiveness and scratch pattern?
 
bucketstove said:
Why is it important that sandpaper maintain its aggressiveness and scratch pattern?
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It's not,

It's just a fact that as soon as you start using the sandpaper it starts breaking down and the grit changes, becoming finer. This is great for polishing or just making a nice smooth scratch pattern but the problem starts when you continue to use the same sheet of paper for multiple knives. For example: if you are setting bevels on 3 knives with 220 grit wet/dry the first knife will be ground quickly but as you move to the next knife the paper become less aggressive and grinds a little slower. By the time you reach the third knife the paper feels smooth on the blade and you notice a considerable lack of cutting speed. This is just the nature of the abrasive and is not a problem but just something to be aware of.

The reason I say it's a single use item is because if I use a sheet of 400 for more than one knife I don't get the same results. The used paper is always finer and slower which is not always a bad thing, but when consistancy is key you can't have constantly changing variables.
 
Jason B. said:
It's not,

It's just a fact that as soon as you start using the sandpaper it starts breaking down and the grit changes, becoming finer. This is great for polishing or just making a nice smooth scratch pattern but the problem starts when you continue to use the same sheet of paper for multiple knives. For example: if you are setting bevels on 3 knives with 220 grit wet/dry the first knife will be ground quickly but as you move to the next knife the paper become less aggressive and grinds a little slower. By the time you reach the third knife the paper feels smooth on the blade and you notice a considerable lack of cutting speed. This is just the nature of the abrasive and is not a problem but just something to be aware of.

The reason I say it's a single use item is because if I use a sheet of 400 for more than one knife I don't get the same results. The used paper is always finer and slower which is not always a bad thing, but when consistancy is key you can't have constantly changing variables.
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Are you using sandpaper dry or with water or oil ?
Are you cleaning the sandpaper in between uses? Eraser?

To me it doesn't seem like too much of an adjustment, going from 30pps (1min) to 300pps (5min)
with something "very fine" like 220 grit
Also going from < 1lb to < 5lb of force
but yeah, the coarser sandpaper is easier to keep clean/unloaded/unglazed/uncloged
 
Like most threads on this sub-forum, this one is packed with great contributions. Thanks to everyone that shared their expertise and experience.

I don't have much to add, but I did just buy a Sanding Belt Cleaner from Harbor Freight. I used it on a few sheets of sandpaper that I had glued to balsa, and the abrasiveness of the sandpaper increase significantly afterwards.

FWIW, my current progression for sharpening dull but undamaged blades is as follows:

1 - 400 on balsa, working one side until I get a burr, then working the other side until I get a burr, then alternating sides for +/- 10 strokes.
2 - 600 on balsa alternating sides for +/- 40 strokes.
3 - 1000 on balsa alternating sides for +/- 40 strokes.
4 - Stropman black compound on a cheap and hard Flexcut strop
At this point the edge will shave leg hairs, but I am experimenting with finishing on Stropman white compound on a cheap and hard Flexcut strop.
 
This may be a bit much for this thread but here goes.

There are all kinds of sandpaper and how well they hold up varies greatly. Are they one time use? Usually not but their efficacy does change from the initial use. While it seems that the grit changes or gets finer with use, actually the abrasive density and sharpness of the particles are what's changing. When you use sandpaper or abrasive belts specifically, what you notice is a slowing of abrasion rate and more heat buildup so that you are more likely to burn blades. When to switch out paper? - when it looses efficacy. You will figure this out with practice, just like you will figure out when your knife is too dull for the task at hand. Ceramic abrasives last much longer, structured abrasives also last much longer and structured ceramic abrasives even longer. Straight silicon carbide or aluminum oxide paper lasts much shorter period of time. Of course WHAT you are abrading, the pressure used etc all affect paper longevity. Abrasive binder also affects longevity. Extremely coarse grits - 24 and 36 grit don't last as long since particles get separated from the paper easily. Short version - there is no simple answer.

---
Ken
 
In my experience, it should be used just like a waterstone. If you see swarf building up, clean it off, just as you would with a quick splash of water only in this case its an eraser of some sort.

Use over a hard backing. Used over softer backings the primary wear action is glazing - the only way to counteract this is to apply more force (relatively) which is poor practice on a soft backing anyway, or use over a harder backing to promote more mineral break-down. I have done no studies to prove this, as there are just too may variables to run tests freehand, but anecdotally I get much longer life from wet/dry when used over my Washboard compared to glass or steel as a backer. I attribute this to the higher unit pressure causing increased mineral fracturing. Most papers die from loading or glazing rather than being genuinely spent.

The initial aggressive value of most wet/dry is just like a new diamond plate - not the true value of the rated grit and it won't be until it sees some use. Once broken in it will grind very reliably at a given finish level right up until the last layer is uncovered and being blown out - at which point the paper is truly spent. I usually cut the paper long before I reach this state.

Use a dedicated progression - specific wet/dry grit lasts a long time when it matches the chore. Unlike other fixed abrasives, you cannot just press harder or use it 2x as long to get the same job done without consequences. This is why I started supplying my Washboards with 120 in addition to 320 and 800 - better to use too coarse a grit and run the progression, than trash a grit that's too fine - the 320 isn't enough for some of the clean-up chores needed on neglected knives.
 
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