This is my LEGO Flattening Jig. It works very well. If I had a smaller stone, I would likely have tried a bunch of other stuff first (taping the edges, freehand, etc.) but with these monster stones, it was just too much. The doming on these 12"x3"x1" Arkansas Stones was pretty pronounced, and even after all the work I have put into them, I still have a long way to go.
First, find yourself a nice FLAT base. The flatness of the base will determine the flatness of the stone. On stones this size, a single tile was not sufficient, and since I installed the tiles in our kitchen, there are not two of them in a row that are flat enough to span. Our flat top stove worked very well. We also have a glass-shelved TV stand that I had thought about. I first cleaned the surface as best possible, using a razor-scraper, water, and buffed it nice and dry. It's not perfect, but it's the best I could do with the tools at hand.
The flattening jig relies on the flatness of the base and the incredibly tight tolerances of the LEGO blocks and LEGO wheels.
Now just attach some w/d sandpaper to another FLAT surface (in my case a marble tile left over from kitchen renovations). I use binder clips to keep them in place, partly because I can never justify buying spray adhesive, partly because I had the binder clips in the stationary drawer .
Now flip that over and lap until your sandpaper/tile is riding on all the wheels. If the stone doesn't have a large enough flat area yet, shim the stone with some paper or card stock. I had a bunch of card stock and paper cut up, and was working to get the stone nice and flat. This jig is set up so that all the wheels ride in the same plane. That combined with the flatness of the tile give you a flat stone.
You will notice that the sandpaper/tile ride on AT LEAST four wheels at a time, and most of the time it is riding on six. This keeps the tile in a single plane. True, you only need it to ride on three at a time to keep it in plane, but four provides more stability.
I have found that adding some SiC powder on the surface of the stone when doing the lapping speeds things up. It prevents the need to swap out w/d sandpaper, and it really powers through the stone. I ran the rig dry, partly because it being wet would have made a big mess, partly because I was worried that water would alter the thickness of my shimming medium.
Suggested improvements would be a uniform thickness anti-slip mat for underneath. The jig wanted to slide around in use, so I added the hand hold you can see on the one the right side (it's just a cross bar to hold on to). I also found that it was best to put a couple sheets of paper under the rig, one on each end (not overlapping), to catch the SiC powder and stone dust. If you had a large rubber mat, it would do the same thing. I did my best to re-use the SiC as much as possible, since I had a limited supply to start out with.
I have put broad, flat areas on two stones this way. This one (a Translucent Black Arkansas) and a Black Arkansas. I thought that since both were flat, I could then put SiC between them and flatten away. I was wrong. It doesn't work like that. It wound up re-doming the Translucent Black, and cupping the Black (both very slightly). I guess you live and you learn. I'll be using the jig again to re-flatten the Translucent Black to the point where I can take over flattening them by hand, and to get the Soft and Hard stones well on their way to being flat also. Actually, I will be using it for their bottom sides also, and I'll modify it to use for the edges. These stones will give both large surface areas on the major faces, but also allow me to use them on edge as a long, skinny hone.
I have been thinking about how nice it would be to have a milling machine that could do the work for me . After all this work to flatten the stones, you can bet your bottom dollar that I'll get some good use out of them . I am purchasing more abrasive powders (both SiC and AlOx) to finish flattening them and polish them. By the time all things are said and done, it may have been less expensive to just buy flat stones, or pay someone to flatten them for me . The good news is that the LEGO Flattening Jig cost me precisely $0, since I had the LEGOS on hand (got them for my daughter and I to play with).
First, find yourself a nice FLAT base. The flatness of the base will determine the flatness of the stone. On stones this size, a single tile was not sufficient, and since I installed the tiles in our kitchen, there are not two of them in a row that are flat enough to span. Our flat top stove worked very well. We also have a glass-shelved TV stand that I had thought about. I first cleaned the surface as best possible, using a razor-scraper, water, and buffed it nice and dry. It's not perfect, but it's the best I could do with the tools at hand.
The flattening jig relies on the flatness of the base and the incredibly tight tolerances of the LEGO blocks and LEGO wheels.
Now just attach some w/d sandpaper to another FLAT surface (in my case a marble tile left over from kitchen renovations). I use binder clips to keep them in place, partly because I can never justify buying spray adhesive, partly because I had the binder clips in the stationary drawer .
Now flip that over and lap until your sandpaper/tile is riding on all the wheels. If the stone doesn't have a large enough flat area yet, shim the stone with some paper or card stock. I had a bunch of card stock and paper cut up, and was working to get the stone nice and flat. This jig is set up so that all the wheels ride in the same plane. That combined with the flatness of the tile give you a flat stone.
You will notice that the sandpaper/tile ride on AT LEAST four wheels at a time, and most of the time it is riding on six. This keeps the tile in a single plane. True, you only need it to ride on three at a time to keep it in plane, but four provides more stability.
I have found that adding some SiC powder on the surface of the stone when doing the lapping speeds things up. It prevents the need to swap out w/d sandpaper, and it really powers through the stone. I ran the rig dry, partly because it being wet would have made a big mess, partly because I was worried that water would alter the thickness of my shimming medium.
Suggested improvements would be a uniform thickness anti-slip mat for underneath. The jig wanted to slide around in use, so I added the hand hold you can see on the one the right side (it's just a cross bar to hold on to). I also found that it was best to put a couple sheets of paper under the rig, one on each end (not overlapping), to catch the SiC powder and stone dust. If you had a large rubber mat, it would do the same thing. I did my best to re-use the SiC as much as possible, since I had a limited supply to start out with.
I have put broad, flat areas on two stones this way. This one (a Translucent Black Arkansas) and a Black Arkansas. I thought that since both were flat, I could then put SiC between them and flatten away. I was wrong. It doesn't work like that. It wound up re-doming the Translucent Black, and cupping the Black (both very slightly). I guess you live and you learn. I'll be using the jig again to re-flatten the Translucent Black to the point where I can take over flattening them by hand, and to get the Soft and Hard stones well on their way to being flat also. Actually, I will be using it for their bottom sides also, and I'll modify it to use for the edges. These stones will give both large surface areas on the major faces, but also allow me to use them on edge as a long, skinny hone.
I have been thinking about how nice it would be to have a milling machine that could do the work for me . After all this work to flatten the stones, you can bet your bottom dollar that I'll get some good use out of them . I am purchasing more abrasive powders (both SiC and AlOx) to finish flattening them and polish them. By the time all things are said and done, it may have been less expensive to just buy flat stones, or pay someone to flatten them for me . The good news is that the LEGO Flattening Jig cost me precisely $0, since I had the LEGOS on hand (got them for my daughter and I to play with).
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