Thread: How does Lapping actually work?

The question was “How can you lap a 10,000 grit stone with a 250/400 grit sandpaper, and not have a bunch of scratches in it?” the scratches don’t matter as long as the scratches run parallel to the honing direction. It becomes a matter of aesthetics removing scratches on a hone. Lapping a stone to 8K is a waste of time, effort and 2 stones. Unless it increases performance and you will not know that unless you experiment with that stone.

Flat is a relative term, we are attempting, 1.to get the tops of most of the grit on the same plane, not all the grit. 2. Refract the grit. And 3.Unload/clog the grit, all at the same time.



Attached is a stone I pulled from the slow cooker it’s been soaking for a few days, I suspect/hope it may be a coti… maybe an old ark. It was somewhat yellow when it went into the soup.

Now I could flatten the dished side, it would be purely aesthetics, a waste of time, sandpaper and effort. Instead I will lap the bottom side and test for its cutting/finishing abilities. If you could lap the dished side so all the grit is at the same height and you held the spine on the hone you could sharpen on the dish side of the hone. How does a jointer/surface planer flatten a piece of wood? The cutter head is round, and the blades travel in a circular motion, no?

Many times we do thing just because others say to without asking why? I applaud Clarence for asking why? Get as much information, then do what he thinks is best for him, experiment and see what works. To blindly polish rocks to a mirror finish, just because… is not productive or skill building. Now that is silly.

How many threads have we read from novice honers who have done x laps on 1K-12k as instructed and can’t get a razor to shave? Was it sharp at 1K? No one ever checked, but he did the required laps.
We are not baking cakes.

And as for scratches, I do not see how they matter as long as the surface is overall flat to the bevel. Bevels are thin, but microns are even smaller. Dont forget the fact that In the case of the dished hone up there (after its smoothed out), the effect would be similar to a layer or two of tape on the spine. If you pretend the dish is smooth, and take an arc with the same width as a razors bevel from it, for most intents in purposes it will be flat. Now picture the full blade on it. Even for that distance, the stone is relatively flat. But for humor sake, extend the line of the bevels contact out, and it will pass just under the spine of the razor. The dish only really becomes noticable at the 2" mark, and then more so at the 3" mark. give it a try, scroll up and block of the monitor with a couple sheets of notebook paper to only show different sized sections, ignore the ruler in the picture while doin this.

Euclid,
Honing razors is not easy, but baking a cake isn't exactly a piece of pie either.

Michael

Here, here for bakers, there are bakers and there are… Bakers. True Baking really is much more art than science… even with a recipe. And maybe that makes my point. And you are right Michel, it’s not that easy, anything worth doing well rarely is.

All I’m saying is there is no recipe for much of this, because there are so many other variables. So there only guidelines. X worked for one person it might work for you and your stone. When we tell novices here is the recipe for honing a razor or lapping a stone we may be setting them up for failure because we don’t explain the variables, and we don’t know the largest - the pilot.

Back in the late 50’s Ben Hogan wrote, what at the time people thought was the definitive book on golf. To the dismay of many he wrote down all his secrets. It has sold multiple millions of copies. Why is it, there are only a handful of people in the world that can play golf at Tiger Woods’ level?

All of my finishers have scratches, Thüringen’s, Black & Translucent Arks, c12K and probably Coticlues & Synthetics as well they just don’t show as pronounced. All finish well, no fractured edges that I can see at 100 magnifications or feel shaving on my face. For me, that is what counts.

Lame you are right, if I could figure a way to even out the grit easily and retain the arc, it would make a good experiment, alas I am not that ambitious.

I always seem to have a change of heart when it comes to lapping/soaking/spritzing.

For past few weeks I've been going at 1k Chosera + 5/8/12 SS progression in dry-minimalistic style.
No water on any stones, and occasional lapping only on 1k when setting bevels, and
very light sandpapering with 1200 grit when the SS gets clogged up.
With the minimalist approach, though, I tend to move the razors around to wear the stones down evenly.

My current take is that the razors are as shave worthy as any, I save 10-15 minutes from stone preps, and hands stay dry.


I'm sure in 3 weeks I'll have a change of heart when I get frustrated from dished 8K and go into meticulous lapping/soaking routine for a while.

Speaking of "true flatness" There are items called Gauge blocks. They are used for calibrating measuring equipment, like calipers and such. I came across a set when I was in school for fabrication.

They are steel, and perfectly flat. They are so flat, when you put two together, there's no room for air, so they act as if magnatized. Pretty cool, at least I thought so at the time.

Gauge block - Wikipedia, the free encyclopedia

Recently acquired a hone from JimmyHAD. He had lapped it so well the rubbing stone sticks when you work up a slurry if you push the water out. It sticks well enough to pick the stone up. First class job JimmyHAD.

Lapping does two things.

• Establishes a flat profile
• Removes clogged swarf filled hone stone.

The flat profile is important when switching from hone to hone to hone.
If all hones dished at the same rate this would be almost unnecessary
but they do not wear at the same rate so lapping can help. In my limited
experience hones wear wrong. The coarse hones wear faster and
then the finer hones cannot touch the bevel at the edge. A 10k or
finer hone with a little sway back will produce a nice micro bevel.

Clogged swarf filled hone stone does not cut as fast
as fresh clean stone. A hone that is clogged can glaze over
and get slower and slower. For some barber hones and finishing
hones this is a good thing because it makes the hone cut
less i.e. finer.

I have an extra extra coarse large DMT for lapping flat. I do run a
very very worn old but smaller DMT over my fine hones to smooth
the surface of my finer hones because my big DMT is a bit rough.

I have noted groves on my Norton 8K. As the hone gathers swarf
the deep scratches are visible. As long as I can see these scratches
I consider the hone flat and just rub the swarf off with my hand. The
best Norton 8K edges I get are the third or later razors after lapping. So
yes for me crazy grinding the top of a fine hone is not totally necessary.
Especially because I can see when the hone departs from flat.

Summary:
Lap for flat
Lap to remove swarf when less aggressive tricks fail.

Originally Posted by Euclid440

Here, here for bakers, there are bakers and there are… Bakers. True Baking really is much more art than science… even with a recipe. And maybe that makes my point. And you are right Michel, it’s not that easy, anything worth doing well rarely is.

All I’m saying is there is no recipe for much of this, because there are so many other variables. So there only guidelines. X worked for one person it might work for you and your stone. When we tell novices here is the recipe for honing a razor or lapping a stone we may be setting them up for failure because we don’t explain the variables, and we don’t know the largest - the pilot.

Back in the late 50’s Ben Hogan wrote, what at the time people thought was the definitive book on golf. To the dismay of many he wrote down all his secrets. It has sold multiple millions of copies. Why is it, there are only a handful of people in the world that can play golf at Tiger Woods’ level?

All of my finishers have scratches, Thüringen’s, Black & Translucent Arks, c12K and probably Coticlues & Synthetics as well they just don’t show as pronounced. All finish well, no fractured edges that I can see at 100 magnifications or feel shaving on my face. For me, that is what counts.

Lame you are right, if I could figure a way to even out the grit easily and retain the arc, it would make a good experiment, alas I am not that ambitious.

__________________________________________________ _________________

Euclid,

You are on the ball. Keep posting.........................

Jerry

Originally Posted by niftyshaving

Lapping does two things.
The flat profile is important when switching from hone to hone to hone.
If all hones dished at the same rate this would be almost unnecessary
but they do not wear at the same rate so lapping can help. In my limited
experience hones wear wrong. The coarse hones wear faster and
then the finer hones cannot touch the bevel at the edge. A 10k or
finer hone with a little sway back will produce a nice micro bevel.

This is of course a very good point. The large radius arc, will create a slight convex to the razors edge bevel. When put against a flat stone, it should become noticable under magnification at least. until you wind up re-setting the bevel on the next hone, creating more work & in a staged manner removing more metal than necessary.

When I wrote my post I was more thinking along the lines of slurry to finish, then future touch ups on the same stone. Basically maintaining the same convex edge.





If you dont want to play with that dished stone, I might be interested in experimenting on it. On second thought, probably not. I have learned though here that doing a coti-only sounds like a long involved process. Let alone learning and starting a coti progression on a dished stone, sounds like heck to troubleshoot when I dont have the stone experience, or means to check how the bevel is going for a razor level edge. Means I could only confirm it works, not that it dont work. Only way I could confirm it dont work is over a course of years. And I havent even touched on the battle to consistently lap out a dish. :/ too much for me.