Thread: Does lapping hones cause grit change?

Ok, so please forgive me if this subject has been touched on before. If this subject exists in another thread, just point me there please. This might sound like a silly question but it still seems logical to me. I am asking this as I have lapped a few hones recently and wondered if I am changing the "grit" of the hone?

For example, let's say I have a NOS barber hone or a NOS coticule, doesn't matter what kind of hone it is but we say it has never been used or lapped. Lets say we take a vintage barber's hone that has a grit of 10K. If I lap it with a 250 grit sandpaper yes it will be still composed of the same material, of course, BUT wouldn't the hones surface now be much "rougher" after sanding with a 250 grit? Does not a rougher surface then change the grit of the hone? If we then take the hone and move it up to 500 grit sandpaper and then lap it on that, it now has a smoother surface than it did after lapping with the 250 not possibly not as smooth as it did when it was manufactured. A smoother surface again does not mean a higher grit rating?

I guess I am wondering if I can be taking the optimal honing effects away from a hone if I hone it with too low of a grit of sandpaper or if I go too high with a sandpaper like 1000 grit. Is it possible to put TOO much of a smooth surface on a hone so that it is no longer doing the honing job it was meant to do (with a slightly rougher surface)?

Well, it could.

If you lap something very hard with a very coarse grit, the surface of the lapped stone will be very rough, and could cut like a lower grit than it actually is.

If you lapped something very hard with a very fine grit, you might break down the abrasives in the thing you are lapping without tearing them out, effectively lowering the grit of what you are lapping.

In both cases, once you remove the top layer or layers of the lapped hone, it will regain it's normal cutting properties. On hard stones, this may not happen right away, but on softer ones it will happen quickly.

I'm sure there are other possibilities as well.

Depends on how coarse your tongue is.

James.

Using my Norton 8k for knives I can tell the difference between being lapped with the flattening stone and 1K sandpaper on granite. I say knives cause I have almost zero razor honing experience, but the issue is how it cuts any blade steel, not just razors.

A coarsely lapped stone will have fewer contact points with the bevel.
Think of standing on a pebble vs same size pebbles but many under bare foot. Single pebble hurts more.
Keeping pressure constant, you and your stone are being more aggressive while you hone on course stone vs smooth.
It is not just grit thing but a force thing too.

All previous facts mentioned are at play to, making your question not a one liner answer/
M

By the way, IMPO this is one of the reasons razor sharpening is so different than other edges. Most of us have set some pretty high standards for ourselves with the smooth and sharp at the same time thing. The fact that hone surface changes means that we are constantly adjusting pressure, speed etc. to changing feedback of hone, even when we do not realize it.
M

I guess it comes down to more trial-n-error lapping and honing. I questioned this because about a year ago now I lapped a 3 line Swaty with progessively higher grit sandpaper, going all the way up to 2000 grit. More just experimenting than actually knowing if I was causing damage or not. It, of course, ended up with a very smooth surface, and I wondered if it was TOO smooth to actually do the honing job it was manufactured to do. I also lapped a number of other hones recently, including a BBW, coticule, Chinese 12K, various other barber hones and wondered if it was wise to follow the same progression of sanding with higher grit wet/dry sandpaper. On all of them, I went up to 1000K.

Thanks to all who replied!

Originally Posted by JNT

On all of them, I went up to 1000K.

Could you clarify this? I'm pretty sure that you did not go up to 1,000,000 grit. However, if you did, I'd like to know how!

Sorry! You are right. I meant 1K wet/dry sandpaper.

Originally Posted by holli4pirating

If you lap something very hard with a very coarse grit, the surface of the lapped stone will be very rough, and could cut like a lower grit than it actually is.

This actually happened to me when I lapped a Swaty with sandpaper. I fixed it by rubbing my two Swatys together under a stream of water (i.e. lapping the Swatys with each other).

Not sure. I have lapped CH12Ks, coticules and BBWs on a DMT coarse (~325 grit) and the surface was definitely not 325 grit. I have also followed up the lapping with a DMT fine and could not see any difference in the surface of the hone under 100x magnification.