Question about lapping on my first Jnat

[Smattayu]

I recently purchased this inexpensive Jnat from chef knives to go, and while I was lapping it with some 400 wet/dry on a marble tile, a spot very close to the center of the stone started flaking off. You can see it as the white area near the center and, while it is not very deep it is extremely noticeable. Is this something that I should just lap through, or do I need to take any preventative measures before I continue? The more yellow areas are where the sandpaper hasn't gotten to yet, so there is plenty left to do before this thing is dead flat, but I didn't want to continue if it just going to keep flaking.

 

[buca3152]

I would send that one back. Not worth the trouble to lap past that imo.

 

[Steve56]

Bill's probably right but you could try lapping it a bit more to see if it increases or decreases. If it decreases in size rapidly I'd probably lap it.

That's what Alex Gilmore callas a bias layer crack, a crack that intersects the sirface at a very narrow angle and therefore is unstable at its edges. It could get better or worse as you lap.

Other than that, it's a pretty nice looking stone.

Cheers, Steve

 

[eKretz]

I've got one with nearly identical coloring that's a great performer. Of course that's not to say that yours will be also - but I'd at least lap it a bit and see if the flake gets bigger or smaller like Steve suggested. Might be a really nice stone if you give it a chance. Maybe contact the seller first and make sure it won't be a problem to return it you do lap more away.

 

[Smattayu]

Thanks guys! I did lap it down farther and the flaking area started diminishing almost immediately. It took about half an hour to get all the way through it, but there is no sign of it now. The down side is that the stone ramps down a little at both ends about 1-2mm and, judging by how long it took to get this far, getting it completely flat is going to take a while lol.

 

[Jnatcat]

The stone will have to be very flat all the way across it, you can draw pencil grid lines and using either WD sandpaper with a flat tile or a lapping plate the lines should wear evenly off if they come off in the middle and not the ends you need to lap it more, the same goes if off the ends and not in the middle, if it's not flat the razor will never touch this low spots.

 

[Steve56]

Draw a line where the low areas begin and post an image. You may well be able to just ignore them.

Cheers, Steve

 

[Smattayu]

The stone will have to be very flat all the way across it, you can draw pencil grid lines and using either WD sandpaper with a flat tile or a lapping plate the lines should wear evenly off if they come off in the middle and not the ends you need to lap it more, the same goes if off the ends and not in the middle, if it's not flat the razor will never touch this low spots.

Draw a line where the low areas begin and post an image. You may well be able to just ignore them.

Cheers, Steve

Thanks guys. Here is a pic that illustrates the size of the stone as well as showing the low spots. I've got the middle of it dead flat, and can hone a razor on it, but I'd prefer to be able to utilize the upper area as well, which is the lowest of the two.

 

[Jnatcat]

Thanks guys. Here is a pic that illustrates the size of the stone as well as showing the low spots. I've got the middle of it dead flat, and can hone a razor on it, but I'd prefer to be able to utilize the upper area as well, which is the lowest of the two.

You are going to have to lap that stone quite a bit, you can use WD sandpaper with a piece of granite tile but it's best to invest in a lapping plate, i tried using paper but honestly a plate like an Atoma 400 pays off in the long run.

 

[Smattayu]

You are going to have to lap that stone quite a bit, you can use WD sandpaper with a piece of granite tile but it's best to invest in a lapping plate, i tried using paper but honestly a plate like an Atoma 400 pays off in the long run.

That's what I was figuring. I've already gone through embarrassing amounts of W/D, though I had also had SIC powder mentioned. The Atoma is likely to go into the cart soon regardless lol.

 

[Steve56]

I think it's usable like it is - might want to get the narrow area on the upper right a little flatter, but do you really have the edge or spine on those areas much while honing?

Cheers, Steve

 

[Jnatcat]

You can send it to me and i will be happy to lap it free of charge just cover round trip shipping, PM me if interested, i would lap with a 400/1200 Atoma and burnish with a Tomo

 

[Smattayu]

I think it's usable like it is - might want to get the narrow area on the upper right a little flatter, but do you really have the edge or spine on those areas much while honing?

Cheers, Steve

It is very likely usable as is, but at this point it is probably more of an OCD thing than whether it's usable or not lol.

You can send it to me and i will be happy to lap it free of charge just cover round trip shipping, PM me if interested, i would lap with a 400/1200 Atoma and burnish with a Tomo

Thank you for the very generous offer, PM sent.

 

[Jnatcat]

Eric,

The stone puts a pretty decent edge on a razor but you have to get creative on the stroke, kind of ago down the side and turn at the 45 and go a tad further

View attachment 710272

 

[Smattayu]

Awesome, thanks again Will.

I just finished a Shumate 333 on it, and it's on deck for tomorrow's shave.

 

[Jnatcat]

Awesome, thanks again Will.

I just finished a Shumate 333 on it, and it's on deck for tomorrow's shave.

Let us know how it shaves, I finished the Ben Hur on it and the shave was very smooth.