Thread: Flattening Glass Plate....

I thought that float glass plate was reasonably flat. I was wrong. I picked up 4-¼ inch glass plates (3" x 11") from a local glass/mirror place and lapped them on my DMT lapping plate. All four were certainly not flat but flattened easily with some effort on the lapping plate. I did it dry. I got these plates in anticipation of receiving some lapping films to evaluate how the new lapping films compare to stones, cubic boron nitride slurries on various substrate, and strops.

All four plates needed flattening. Two plates has several high spots that required significant work to flatten them (about 30 minutes of lapping). The other two, while needing flattening as well, had minor high spots that leveled off within about 10 minutes of lapping. The DMT metal lapping plate works well at flattening glass.

Originally Posted by DoctorSaul

I thought that float glass plate was reasonably flat. I was wrong. I picked up 4-¼ inch glass plates (3" x 11") from a local glass/mirror place and lapped them on my DMT lapping plate. All four were certainly not flat but flattened easily with some effort on the lapping plate. I did it dry. I got these plates in anticipation of receiving some lapping films to evaluate how the new lapping films compare to stones, cubic boron nitride slurries on various substrate, and strops.

All four plates needed flattening. Two plates has several high spots that required significant work to flatten them (about 30 minutes of lapping). The other two, while needing flattening as well, had minor high spots that leveled off within about 10 minutes of lapping. The DMT metal lapping plate works well at flattening glass.

Thanks for sharing. I was honestly not aware of this. I have never used such a thick piece of glass, though.

The great advantage of glass over sharpening stones, is that you can check it easily. Just hold it near your eyes, at a tangent angle, and it should reflect a straight image, not a wavy one. Very high-grit stones might do the same; mines don't (up to 8000, Norton brand). Most stones just don't reflect an image at all.

I had good luck with 12x12 marble tile being flat...works great for a sheet of sandpaper.

Originally Posted by shooter74743

I had good luck with 12x12 marble tile being flat...works great for a sheet of sandpaper.

+1

Same here the shops surface polish the marble so the chances are much higher of "Flat"

I'd do a search on "lapping film" before starting a whole new topic on reinventing a method that has already been discussed at large on the forum.

Originally Posted by MT4

Thanks for sharing. I was honestly not aware of this. I have never used such a thick piece of glass, though.

The great advantage of glass over sharpening stones, is that you can check it easily. Just hold it near your eyes, at a tangent angle, and it should reflect a straight image, not a wavy one. Very high-grit stones might do the same; mines don't (up to 8000, Norton brand). Most stones just don't reflect an image at all.

They're not that thick. I should have written it as "four ¼ inch thick plates". Not the way the post reads. I did price ½ inch plates, but they were $30 each. The ¼ inch plates were $8 each. Big difference, so I went with the ¼ inch plates. Intuitively, the ½ inch plates should be more stable in terms of flatness, but I don't really think there would be a significant difference in varying from flatness due to instability (flow) in my lifetime.

Originally Posted by mainaman

I'd do a search on "lapping film" before starting a whole new topic on reinventing a method that has already been discussed at large on the forum.

Have to agree with Stefan here

Film has a few followers, but it also has many others that just won't use it

IME it really comes down to the razors that you are honing, Film works just fine with straight edged, harder steel, and is a bit lacking when used on others..

Not better or worse just more limited then hones..

But yes there is quite a bit of info on here by simply searching "Lapping Film"

Originally Posted by mainaman

I'd do a search on "lapping film" before starting a whole new topic on reinventing a method that has already been discussed at large on the forum.

Thanks for the advice, Stefan. I've been reading up on lapping films (my thanks to Euclid440) and want to try them out myself, just for fun. I needed a very flat substrate, which is the reason why I bought the four glass plates and lapped them to flatness.

Originally Posted by MT4

Thanks for sharing. I was honestly not aware of this. I have never used such a thick piece of glass, though.

The great advantage of glass over sharpening stones, is that you can check it easily. Just hold it near your eyes, at a tangent angle, and it should reflect a straight image, not a wavy one. Very high-grit stones might do the same; mines don't (up to 8000, Norton brand). Most stones just don't reflect an image at all.

The glass plates are not that thick. I bought four glass plates locally. They were ¼ inch thick, and measured 3 inches x 11 inches. I should have spelled out "four" to avoid the misread.

Here in Bulgaria there is no lapping films , and i whant to try them so badly . Where can i order them , the best quality at the best prise . I have heard only good words for the lapping films .
And 30 $ for a glass plate , wow bwtwr buy a sharpening stone or cut your self a piece of domestic glass .
Glass with paste on it works fine , a little bit slow but fine .