Thread: Does lapping hones cause grit change?

Originally Posted by Johnny J

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).

Yup, I had the same experience. A Swaty used to be my universal hone scratch remover (once I lapped it) because it was smooth and wear resistant. I have a pocket sized Spyderco Medium that works well for this too.

Originally Posted by JNT

... I am asking this as I have lapped a few hones recently and wondered if I am changing the "grit" of the hone?

No, but depending on the finished surface roughness you may be changing the surface area in contact with the razor, as Kingfish was saying. The rougher the finish on your hone the less metal in contact with the hone and the faster it will cut leaving larger and deeper scratches. This may appear as if the grit is changing but you are just changing the amount of metal removed over the entire length of the bevel. A slurry has a similar effect but is controlled bu the particle sizes on top of the hone and not the depth and hight of the peeks and valleys left after a rough lapping.

You are getting a faster cut because the surface area is changing not the grit size.

So am I doing myself a disservice lapping my Naniwa 12K on a DMT 325? I.e., am I making it less of a finishing stone than I want it to be?

I've seen it advocated elsewhere (a knife forum, I think) to lap each stone successively on the next. For me I guess that would mean my 1k on my DMT 325, my 4k on my now-flat 1K, then my 8k on my 4k, etc. I've never tried this, but it sounds logical if the stones are close to flat, and if the slurry from the courser stone doesn't clog the finer. Anyone tried it?

Originally Posted by JackJ

So am I doing myself a disservice lapping my Naniwa 12K on a DMT 325? I.e., am I making it less of a finishing stone than I want it to be?

I've seen it advocated elsewhere (a knife forum, I think) to lap each stone successively on the next. For me I guess that would mean my 1k on my DMT 325, my 4k on my now-flat 1K, then my 8k on my 4k, etc. I've never tried this, but it sounds logical if the stones are close to flat, and if the slurry from the courser stone doesn't clog the finer. Anyone tried it?

It's relative. There is a point where the scratch pattern on your hone from lapping has a minimal effect on scratches. There are times where I finish lapping on the 325 DMT and times when I rub the hone with the next lower grit. Experiment with the different techniques and gauge the results fro your self. Also, a few laps on the hone w/ a junk razor or other piece if metal will help 'condition' the hone before you run a good razor over it.

A lot depend on how hard is the hone. If it is soft ish i.e. Naniwa I do not think there is difference. But use something like DT (a few members here have) and there is difference in scratch pattern depending on coarseness of lapping.

So am I doing myself a disservice lapping my Naniwa 12K on a DMT 325? I.e., am I making it less of a finishing stone than I want it to be?

No!


Your Naniwa 12k will be just fine if you lap it with your dmt 325.
The 325 is a very good lapping tool that leaves a closed surface.
So no, your 12ks finishing abilities will not be diminished.

With normal synthetic stones like shapton, norton and naniwa think of it as this:

These stones are like a box filled with sand. The sand is the abrasive.
If you scrap through the sand, you will create little waves and unevenes.
That´s what the stones surface may look like after lapping it really coarse.
But by doing so, did you change the size of the sand grains?
No you did not. The grain size is unaffected.

However there are stones that act differently.
Extremeley hard stones like Spyderco, Barber hones or Arkies for example
don´t have anctual grits but a surface that does the job.
If you change their surface, you may change the way they act

kingfish and joed thank you .you both correct. Grit will not change doesnt matter how low grit or high grit sandpaper you use to lap the stone. Stones sharpening quality will change by using different pressure. As they both mentioned when do you use lower grit lapping plate it basically will make deep scratches and contact with the stone serfice and blade will be less as a result wil take more time to hone blade. Now you can feel finer stone after lapping sometimes it is because old stones durty as soon as you clean them up they will act better. This doesnt mean you changed grit of the stone. Another case is this old barber hones sometimes gets bad.their joining compound just looses quality.if you had 1 of that stones they will act as op described. Hope this helps

l

The scratch patterns, though they create an irregularity in the surface, won't effect the blade if an x-stroke is performed. It has to do with averaging the effect of the irregularity. The Wiki has a terrific description:

The limitation on geometric accuracy is overcome in honing because the honing stone follows a complex path. In bore honing for example, the stone moves along two paths simultaneously. The stones are pressed radially outward to enlarge the hole while they simultaneously oscillate axially. Due to the oscillation, each slice of the honing stones touch a large area of the workpiece. Therefore, imperfections in the honing stone's profile cannot transfer to the bore. Instead both the bore and the honing stones conform to the average shape of the honing stones' motion, which in the case of bore honing is a cylinder. This averaging effect occurs in all honing processes; both the workpiece and stones erode until they conform to the average shape of the stones' cutting surface. Since the honing stones tend to erode towards a desired geometric shape, there is no need to true them. As a result of the averaging effect, the accuracy of a honed component often exceeds the accuracy of the machine tool that created it.

Honing (metalworking) - Wikipedia, the free encyclopedia

No, You cannot change the grit of a stone by lapping. You can rough up the surface or texture of the stone, but if it's 12k, it's still going to be a 12k. If the stone is a natural and 12k all the way through, (not just on the surface, like DMT's) You can't change the molecular structure of a rock by sanding it...