Thread: Lapping--what's flat??

I got the Norton set about 2months ago and have been using it quite a bit (almost every evening), trying to get four different razors up and running.

I also have a 1/2" thick granite tile that I picked up at the HD store that I've been using on my 8k Norton and 12k Chinese stone.

Now here's the hangup. When I use the Norton flattening stone on the 4k Norton (per the included Norton DVD), it takes material off the edges. When I use the granite slab and 600# sandpaper, it takes material off of the center. We also have a 1" marble slab for kitchen use (although the finish now less than flawless in many spots). That behaves similarly to the granite tile--material comes off the center of the hone.

So I don't know which one is getting me closer to flat. I'm leaning towards the marble/granite.

What say you? Are there any easy ways to check here at home. I've got some rudimentary tools (basic woodworking, advanced reloading stuff). I

Once soaked does it stick hard to the kitchen counter? You might try soaking it and placing against a vertical piece of glass. The glass will be flat and it should stick to the glass.

Originally Posted by AFDavis11

Once soaked does it stick hard to the kitchen counter? You might try soaking it and placing against a vertical piece of glass. The glass will be flat and it should stick to the glass.

Stick as in not slide down?

You used the pencil grid to see where the material is comming off of the hone, correct?

I would expect to see material comming off of the edge when lapping after significant usage.

I check for flattness using a mrak I eyeball and a straight edge, not real scientific but it works for me.

My way of solving the same dilemma was to buy a Starrett straight edge #385 with one edge beveled. If you're as anal as I am you can find it here. It will tell you if your stone or lapping plate is flat. I got different results between my DMT and my Shapton GDLP. The straight edge enabled me to find the DMT was the problem. I returned my D8C and DMT replaced it. So the straight edge ain't cheap but for me it was worth the $$.

Pencil grid was used.

I have a granite reference plate, grade a quality, with a certificate of flatness. over a 1 foot length, it's flat to within +/- 1.05 microns. Just as a comparison, the shapton lapping plate is only accurate to +/-5 microns.

That means that my granite block could be out a total of 2.1 microns, whereas the shapton glass lapping plate could be out a total of 10 microns!

When I flatten using 3m wet/dry sandpaper, I stick it to the granite slab and go at it, with pencil grids the whole way. I also have a granite tile that I bought from Lowes, and out of curiosity I stuck the 3M wet/dry to it, drew some more grids, and had a go at it. It took off the pencil grids in a few laps very evenly.

When you lay the granite tile on the reference plate, it creates quite a suction! From my lapping, I'd say that the tile is pretty much just as flat. It doesn't come with a certificate of flatness, but who cares?

Consider the following scenario:

case 1: granite tile from Lowes with 320 3M wet/dry sandpaper
case 2: granite slab @ +/- 1.2 microns flat with 320 3M wet/dry sandpaper
case 3: Shapton glass lapping plate @ +/-5 microns flat

If I took three shapton 16K glass stones and flattened them, one on each flattening method, and then had one person hone three identical razors on those hones, no one here could tell which razor was honed on which stone given the proper double-blind experiment. They would all get your razor just as scarily sharp as the next one. I'd bet every strop, razor, and hone I have on this against a pair of Zeepk and Selective razors.

So, yeah, go ahead and get yourself some wet/dry sandpaper, a $5 granite tile from Lowes, and go at it, knowing that your stones are pretty much just as really darn flat as the next guys, and you didn't spend 280 bucks on silly frivolities. Plus, the corners of your sandpaper won't dig into your hones like DMT's sometimes are prone to do.

BTW, why do I see all these people getting marble tiles from lowes? Have you ever walked into a machine shop and seen someone checking flatness against a piece of marble? Get granite.... it's better...


BTW #2: Anyone who ever recommends the Norton flattening piece of turd, outta be shot with sh*t and killed for stinkin'. THAT piece of junk isn't worth it. After a while you have to flatten it, so that just means that you've been flattening your stones with an un-flat surface, and if that's not the definition of dumb, then I don't know what is. Sorry for my strong feelings on this, but it just needs to be said.

Originally Posted by Ben325e

I have a granite reference plate, grade a quality, with a certificate of flatness. over a 1 foot length, it's flat to within +/- 1.05 microns. Just as a comparison, the shapton lapping plate is only accurate to +/-5 microns.

That means that my granite block could be out a total of 2.1 microns, whereas the shapton glass lapping plate could be out a total of 10 microns!

When I flatten using 3m wet/dry sandpaper, I stick it to the granite slab and go at it, with pencil grids the whole way. I also have a granite tile that I bought from Lowes, and out of curiosity I stuck the 3M wet/dry to it, drew some more grids, and had a go at it. It took off the pencil grids in a few laps very evenly.

When you lay the granite tile on the reference plate, it creates quite a suction! From my lapping, I'd say that the tile is pretty much just as flat. It doesn't come with a certificate of flatness, but who cares?

Consider the following scenario:

case 1: granite tile from Lowes with 320 3M wet/dry sandpaper
case 2: granite slab @ +/- 1.2 microns flat with 320 3M wet/dry sandpaper
case 3: Shapton glass lapping plate @ +/-5 microns flat

If I took three shapton 16K glass stones and flattened them, one on each flattening method, and then had one person hone three identical razors on those hones, no one here could tell which razor was honed on which stone given the proper double-blind experiment. They would all get your razor just as scarily sharp as the next one. I'd bet every strop, razor, and hone I have on this against a pair of Zeepk and Selective razors.

So, yeah, go ahead and get yourself some wet/dry sandpaper, a $5 granite tile from Lowes, and go at it, knowing that your stones are pretty much just as really darn flat as the next guys, and you didn't spend 280 bucks on silly frivolities. Plus, the corners of your sandpaper won't dig into your hones like DMT's sometimes are prone to do.

BTW, why do I see all these people getting marble tiles from lowes? Have you ever walked into a machine shop and seen someone checking flatness against a piece of marble? Get granite.... it's better...


BTW #2: Anyone who ever recommends the Norton flattening piece of turd, outta be shot with sh*t and killed for stinkin'. THAT piece of junk isn't worth it. After a while you have to flatten it, so that just means that you've been flattening your stones with an un-flat surface, and if that's not the definition of dumb, then I don't know what is. Sorry for my strong feelings on this, but it just needs to be said.

After reading this post [and a few others regarding the DMT v. granite tile], I finally decided to go with the less expensive [and probably more accurate] granite tile.

Last night I called both Lowes and Home Depot for prices--$5.49 per tile at both stores. I got lost on the way to Home Depot [because I am a moron], but I saw the Lowes parking lot. They were/are having a clearance sale on single granite tiles--$2.19 each--and there was only one tile left. It was the "Bianco Catalina" style. And what is my last name? B-I-A-N-C-Oh my GOSH, it must be fate! =)

I now own a 12x12 granite tile...and sandpaper.

Thanx,
Christopher =)

Here's my little trick - I do not use sandpaper but I raise slurry on the lapped surface, and then make the slurry do the abrasive job. This works very well for me, the glass is much harder than hones and you get very fine surfaces with this method.

I do not use a granite tile but a thick sheet of glass. I will probably get the granite as it must be more convenient to store, clean etc.

For initial lapping when a lot of material needs to be removed, I do not use slurry but valve grinding compound from Napa autoparts. It is coarse and lightning fast.