Norton Lapping Problem

[bmhodges]

First off I am a beginner and by no means do I know what I am doing as of yet. Now for the question. I purchased a norton 4k/8k and DMT 325. I lapped the 8k and a Naniwa 12k with no issues. Now the 4k has lapped uneven by 1/8" on the width of the stone - 3in. First question can this be corrected with lapping the high side or would it be better to buy a new one. Next what would cause this because I used the figure 8 method? Thank you

[toovira]

The regular practice here is DMT to lap the stones. Personally, I'm not a big fan of that. I prefer to have this

Buy Granite Surface Plate at Woodcraft

So you can have enough surface area to do a proper lapping. All you have to do is then go buy sandpaper kit from Advanced Auto ($5 3M brand, 220 to 1000 grit).

Buy 3M Wetordry™ Sandpaper Sheet, 9" x 11", Assorted, 4 Sheets Per Pack 03021 at Advance Auto Parts

Wet the granite, put paper on top, wet the paper, then wet sand the stone with figure 8. To answer your question, it'll probably be a good idea to make both sides parallel. So sand off the higher side, then figure 8 lap it. Use 220 or lower so it's fast cutting. Rinse often....better yet, do it under a running faucet. It'll cut faster. DO NOT APPLY PRESSURE....let the speed do the work....you should not be applying downward pressure. Then work up the grit to the surface smoothness you want.

What would cause it? I can probably tell you that it's probably you. DMT is about the same size as the Norton....it can easily roll off edges.....plus your holding DMT in one hand and Norton in the other - 2 moving stone for perfect flatness won't work well unless you are very experienced.

[toovira]

Also note that you are going to use a full 9x11" sandpaper on top of 9"x12" Granite flat reference (yes, it comes with flatness measurement and certification). Damn thing weighs about 20 pounds.....you just set it on the table, it won't go anywhere.

[bmhodges]

The only problem is that I am in Afghanistan and it is pretty hard to get granite, that is why I bought the DMT 325. I believe the problem is because I was trying to take the recommended 1/8" and probably not holding the DMT correctly. I guess that all comes with practice. Thank you for the responses.

[lz6]

If your 8k and 12k lapped just fine with your 325 there is no reason why you should not be able to level your 4k. Figure 8
might help. Draw the pencil line grid on your 4k and if you can lay hone flat and keep it from moving around use your 325
in the figure eights and just regular strokes until your pencil grid is removed. Pay attention to the 325 to be sure coverage
is as equal as you can make it.

[dave5225]

Also note that you are going to use a full 9x11" sandpaper on top of 9"x12" Granite flat reference (yes, it comes with flatness measurement and certification). Damn thing weighs about 20 pounds.....you just set it on the table, it won't go anywhere.

Although there is nothing wrong with using the super flat granite slab . For all practical purposes , a plate glass cutting board , available from Wal Mart or Target for <$5 will do just as well . Or any other hard , flat surface .

[gssixgun]

Let the 4k tell you how much to lap off, don't just take off an 1/8 inch some of those recommendations came from when the Norton 4k's were first made in Mexico they were a bit rough... Most of the ones I see now are made in Italy and don't need that heavy lapping,, get it even with the grid lap like LZ6 just pointed out and run a razor over it see how it feels. It it is a smooth cutter then stop lapping, all these 4k have a gritty feeling but if it needs heavy lapping it will feel really gritty like you don't want to even run a razor over it...

If you google "gssixgun, norton, lapping" you will find a vid I applogize for having my shoulder in the way but you can get a good idea of what I am doing...

[tekbow]

A lot of the time people get obssessed over relative flatness (IMO). Not to say a hone shouldn't be flat, it should, very flat, as flat as you can make it, but i wouldn't get in there with a spirit level or anything. YMMV but i find any decent flat hard surface will do the job. I use my kitchen counter, wet with sandpaper sticking to it and my hones get lapped just fine. I also like the bigger surface area as was noted above

[zib]

Although there is nothing wrong with using the super flat granite slab . For all practical purposes , a plate glass cutting board , available from Wal Mart or Target for <$5 will do just as well . Or any other hard , flat surface .

Agreed, Even a countertop, or a piece of floor tile will work, marble, or whatever....It doesn't have to be .0000001 flat....
Also, Like Glen was saying, As far as the Norton's go, your looking for smoothness, Once you get the rough feeling gone, your good to go. Make sure your lapping gridlines are gone, which I'm sure they will be at that point....

[bmhodges]

Thanks for the great info, my nortons is flat and smooth just lop sided, I can lap a grid and it will remove evenly. I am going to level it out and then grid it again then I should be fine from all the info. Thanks all