Should a granite lapping/surfacing plate with wet/dry sandpaper be okay for flattening honing stones?
Anyone seeing this use one?
Anyone seeing this use one?
Granite lapping plate okay for flattening stones?
- Thread starter Brassplyer
- Start date
That's what they are for.
I would be careful when using a granite surfing plate with a stone that is known to shed grit particles. Any loose particles of silica dioxide or aluminum oxide (the main components of natural Jnat stones) will cut steel and or stone. Laying a stone to determine flatness is one thing on a granite plate is one thing, but using a grantie plate as a tool/surface for flatening a third-party stone will create a 3-part abrasive scheme and all you will end up with is a concave part 1 and a convex part 2. The plate surface will usually deform and become undependable.
Honing a razor or knife is an exercise in give and take, stone vs steel, all winning is a compromise.
Alx
Honing a razor or knife is an exercise in give and take, stone vs steel, all winning is a compromise.
Alx
I lay a sheet of wet dry paper over my granite. There is probably better ways but I have it handy.
- Thread starter
- #5
Thanks - I would think that as long as nothing gets between the sheet of abrasive and the granite it won't be an issue. I find the motion of the stones stay completely on the abrasive sheet which mostly covers the plate. A film of water between the plate and abrasive sheet and a couple of fingers on the edge of the abrasive sheet keeps it locked in place.
It works very well. I use this system and it is much more accurate than most of the diamond plates out there. The only diamond plate that comes close is the DMT diaflat. One thing to bear in mind is that these granite plates are very heavy. It may not be the most practical solution because it is very bulky. It does give a nice big working surface though. It’s also nice for finishing stones and adjusting the surface prep of things like arks since you can fine tune the grit. It’s a great follow up to the DMT diaflat which is fast and rough. I’ve found the two systems to agree within a very tight tolerance.
I use double sided tape to hold the edges down. You do need to be careful to not let slurry spill over the edge of the paper but it’s pretty easy if you’re careful. If you want to be safe you could fully tape the whole side. You can also put loose sic on top of the sandpaper to get more life out of each sheet. Just be mindful not go through the paper. It takes a long time but after a while you will see the paper showing through. This happens faster on the finer grit paper.
If you mop up the slurry up with paper towel before removing the sheet you won’t spill any slurry onto the stone. It’s worth picking up a few rubber blocks at the hardwear store to put the stone onto. It holds the stone in place and will stop it scratching up any surfaces. It also makes it easier to get your fingers underneath when you want to pick it up again. My small-ish stone weighs 10kg.
Wipe any dust off the back of the paper before putting it onto the stone. Stick the paper down with double sided tape to stop it sliding around. Make sure that you don’t get any slurry under the paper. If you do that you will have a very accurate and versatile system.
I use double sided tape to hold the edges down. You do need to be careful to not let slurry spill over the edge of the paper but it’s pretty easy if you’re careful. If you want to be safe you could fully tape the whole side. You can also put loose sic on top of the sandpaper to get more life out of each sheet. Just be mindful not go through the paper. It takes a long time but after a while you will see the paper showing through. This happens faster on the finer grit paper.
If you mop up the slurry up with paper towel before removing the sheet you won’t spill any slurry onto the stone. It’s worth picking up a few rubber blocks at the hardwear store to put the stone onto. It holds the stone in place and will stop it scratching up any surfaces. It also makes it easier to get your fingers underneath when you want to pick it up again. My small-ish stone weighs 10kg.
Wipe any dust off the back of the paper before putting it onto the stone. Stick the paper down with double sided tape to stop it sliding around. Make sure that you don’t get any slurry under the paper. If you do that you will have a very accurate and versatile system.
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That looks like a perfect setup.
Alx
Alx
I like to use float glass as my base. I only use it for arks though. For my other naturals I will just use my atoma.
- Thread starter
- #9
Thanks - what are the specifics on the abrasive sheet you're using?
“I would think that as long as nothing gets between the sheet of abrasive and the granite it won't be an issue”
But it does, and when it does it will take the surface plate out of flat. The primary purpose of a Certified Flat Surface Plate is for calibration, (measuring flatness) as a known flat surface, not to flatten, though many folks do.
(Surface Plate Calibration and Conditioning)
It is, according to folks that calibrate and certify surface plates, what takes surface plates out of flat. Just wear from airborne dust and tools riding on the dust will take a plate out of “calibration” flat. If your plate is not certified, it is not really that flat any way.
Fortunately, the absolute flatness of a stone is not “that” critical for honing knives and razors. Flattish is good enough.
Granite, marble and glass are really relatively soft and can easily be shaped with sandpaper or other abrasives. Glass is very soft and not as most folks think all that flat. A glass tile can easily be flattened with a sheet of 220.
Granite is used for surface plates because it is relatively stable, not because of it’s hardness.
If you are flattening stones that are way out of flat, loose silicone carbide will hog away material much faster and efficiently. I use 60 grit silicone carbide on a steel cookie sheet on a 20x18 inch granite sink cut out on the cement floor. Steel will wears much more slowly than granite or glass and $1 cookie sheet contains the messy swarf.
If you use wet & dry to lap an Ark, you will go through a lot of paper and will get very tired.
For softer stones like synthetics and naturals, non-novaculites, a 140-400 diamond plate works best and is inexpensive.
You can buy an assortment of Silicone Carbide grit from GotGrit.com from 60-500 for $15, ¼ pound, enough to do several stones, you will use more 60 grit than the others.
A lot depends on the stones and how out of flat they are.
But it does, and when it does it will take the surface plate out of flat. The primary purpose of a Certified Flat Surface Plate is for calibration, (measuring flatness) as a known flat surface, not to flatten, though many folks do.
(Surface Plate Calibration and Conditioning)
It is, according to folks that calibrate and certify surface plates, what takes surface plates out of flat. Just wear from airborne dust and tools riding on the dust will take a plate out of “calibration” flat. If your plate is not certified, it is not really that flat any way.
Fortunately, the absolute flatness of a stone is not “that” critical for honing knives and razors. Flattish is good enough.
Granite, marble and glass are really relatively soft and can easily be shaped with sandpaper or other abrasives. Glass is very soft and not as most folks think all that flat. A glass tile can easily be flattened with a sheet of 220.
Granite is used for surface plates because it is relatively stable, not because of it’s hardness.
If you are flattening stones that are way out of flat, loose silicone carbide will hog away material much faster and efficiently. I use 60 grit silicone carbide on a steel cookie sheet on a 20x18 inch granite sink cut out on the cement floor. Steel will wears much more slowly than granite or glass and $1 cookie sheet contains the messy swarf.
If you use wet & dry to lap an Ark, you will go through a lot of paper and will get very tired.
For softer stones like synthetics and naturals, non-novaculites, a 140-400 diamond plate works best and is inexpensive.
You can buy an assortment of Silicone Carbide grit from GotGrit.com from 60-500 for $15, ¼ pound, enough to do several stones, you will use more 60 grit than the others.
A lot depends on the stones and how out of flat they are.
I Lap everything with Atoma plates and check flatness with a Starrett straight edge.
Stones are flat, always. They're not going to get flatter lapping them any other way.
At one time, when I had a literal ton of Arks to lap, I considered getting a 6" wide granite reference plate and cutting it down to 9-10" long.
But it would still weigh 13 lb, more than I wanted to deal with. I always lap under running water so the granite's corners would have prob wrecked my sink. I wound up killing the back of a dead 10x3 DMT Diafine instead.
Stones are flat, always. They're not going to get flatter lapping them any other way.
At one time, when I had a literal ton of Arks to lap, I considered getting a 6" wide granite reference plate and cutting it down to 9-10" long.
But it would still weigh 13 lb, more than I wanted to deal with. I always lap under running water so the granite's corners would have prob wrecked my sink. I wound up killing the back of a dead 10x3 DMT Diafine instead.
3m Silicon Cardide Wet Dry Sandpaper.
Atomas are good quality plates and very user friendly. No agreements there. I have a couple and they are by all means good enough for the job of lapping razor stones. That aside they are far from perfect and you can almost certainly get a stone flatter. For a soft stone that you use with slurry it probably doesn’t matter. For a hard stone like an Ark it might be worth the trouble.
If you have more than one Atoma try this. Lap a stone until you can remove all pencil grids with a couple of light laps. Redo the pencil grids and lap the same stone with a different Atoma. When I do this with my Atomas I get a different pattern that is not easily removed with a few laps. I have to lap for a few more minutes until the stones surfaces matches the profile of the new Atoma plate.
Atoma does not make any claims about the flatness of their plates and their construction introduces many opportunities for error. First they start with a metal plate of unknown flatness. Whether it has been machined, checked or certified is unclear. Then further layers of unknown thickness are added; double sided tape and a metal sheet. Finally little piles of diamond are added in clumps. Over time the piles wear down. It’s unlikely that they wear evenly across the surface of the plate. Probably more in the middle. Then you have the issue of edge overrun on the small plate. The errors compound.
But nothing is perfect and nothing is perfectly flat. Some things are just much closer than others. Granite surface plates are checked and they come with a report that tells you how close they are. Atomas do not. Like everything else granite plates vary in quality and like anll tools used for precision measurements they should be checked periodically. Even then all bets are off when you introduce temperature gradients across the stone. The same happens with a whetstone. If one side is warmer than the other it warps (ever so slightly). But the effect is measurable by a few microns.
Straight edges are a good check depending on their quality, age and how they are used. Even when used with feeler gauges the best straight edges are limited to measurements of around 0.02mm or 20 microns.
Luckily for us even imperfect tools can create perfect shaving edges. In this instance close enough is good enough.
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Any surface you lap a stone against is going to wear to some degree. Even if the in no grit between the sandpaper and the plate, the only thing between the grit and the plate is paper. If your just using it for finish work and you move around the plate to try to spread the wear out it should stay reasonable flat for a while. If you do heavy work directly in the center over and over again it will go out of flat quickly. I'm willing to bet that 9 out of 10 of those inexpensive grade b granite plates have seen sandpaper.
You guys crack me up. As if a piece of sandpaper is even close to flat, if you are measuring to that degree. You could start with the flattest surface in the world, the moment a bit of paper with sand glued to it is put on top, all bets are off.
But it's still close enough.
But it's still close enough.
I thought it, you wrote it lol
I find value using my reference block lightly if ever. I use it to check my stones don’t spin after flattening. I also used it to true my straight edge (and know I can redo it if need be). That way I got away with a less expensive one. Probably not as dead flat as a Starret, but meets my needs. I see a bump up in final edge quality when I take the time to flatten stones well.
For most work I like a counter off-cut with sandpaper as others mentioned. I also add a silicon baking sheet to help protect the marble. If flattening needs rough work, 60# sic helps. If it’s really hairy, sidewalk concrete for rough work and a bucket of water.
For most work I like a counter off-cut with sandpaper as others mentioned. I also add a silicon baking sheet to help protect the marble. If flattening needs rough work, 60# sic helps. If it’s really hairy, sidewalk concrete for rough work and a bucket of water.
