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Large Honing Grit Jumps, How Large is Too Large?

If I remember right, I read somewhere that you want no more than aka <= a sq rt jump in microns. So 25 micron to 5 micron or more (~600 grit (US/mesh) to ~3k(Us/mesh) grit), 9 micron to 3 micron (~1k(us/mesh) grit to ~8k(us/mesh) grit) or more. Seems to be reasonable... but overthinking it imho... good as a baseline/approximation maybe.

Practical experience? Depends a whole lot on how fast the stones are. I do anything (60 grit, 120 grit, 600 grit) to 1200 (9 micron) to 8000 (3 micron) to finisher (~1 micron or so)... and any finisher that isn't fast enough to go to off 8k, I don't bother with.

I've done 200, 300, 600, 1k, 2k, 3k, 4k, 5k, 6k, 8k, 10k, 12k and every combination of them you can think of. I get the same results with 1k, 8k, finisher. My 8k is very fast though. But everyone hones differently.
How does the use of slurry affect the grit jump (synthetic stones)? Slurry seem to speed up the process considerably. The abrasion also seem to be concentrated more around the apex and a little behind the edge. I do not care that much about how my bevel looks, as long as i have a refined and clean edge.
I have not had that much success using slurry on synthetic finishing stones. The edge seem to degrade as appose to what happens on natural stones. I have also tried synthetic slurry on jnat's, which turned out to be a waste of time.
DrMatt uses slurry all the way to an 8k shapton without issues. So can you manage a grit jump from say an 1k to 8k just by using slurry and finish on water to reduce some of the damage inflicted by the slurry?
What about natural stone slurry on synthetic stone?
I didn't do much with slurry. Always wondered how to raise it without polluting or scarring the hone unless you have a piece of the same stone... Which would be difficult/expensive with synths. Used the king nagura stone a bit on my softer and coarser stones to space out lapping/flattening requirements and felt like not a lot of speed added for a lot grittier and worse results off the stone.

Autoslurry on the other hand does help on stones that do it (not all stones will give up much with razors)
I didn't do much with slurry. Always wondered how to raise it without polluting or scarring the hone unless you have a piece of the same stone... Which would be difficult/expensive with synths. Used the king nagura stone a bit on my softer and coarser stones to space out lapping/flattening requirements and felt like not a lot of speed added for a lot grittier and worse results off the stone.

Autoslurry on the other hand does help on stones that do it (not all stones will give up much with razors)
When i tried different slurries on synthetics i just used one end of a different stone. They do not have to be the same grit as long as it is as fine or finer then the base stone. I dropped my Naniwa Super Stone 12 and broke it a few years a go. It is quite effective if used as a nagura or even as a cleaning stone for vetrified diamond stones and other stones that load up.
Naniwa sells separate nagura Super Stones. Maybe it is more suitable for knife polishing though.
Slurry on a synthetic is very different from Natural slurry on a Slate or Jnat.

Synthetic slurry is of a known grit, say 1k. It does not break down it remains 1k. Yes, it will polish/abrade more aggressively and more so, at the edge.

Imagine taking a fall on asphalt, gravel imbedded in tar, and taking a fall on a loose gravel road, which will tear up your skin more?

As the blade rides on the grit, it has some give, forward pressure will cause the leading edge to dive down into the grit, this will abrade the leading edge more than the back of the bevel, and the same 1k grit will impact the edge, as it dives into the loose grit, dulling it. Again, use the gravel visualization.

So, while loose grit can make a stone more aggressive, it will remove more steel, helpful when bevel setting where the goal is to grind/ flatten the bevels, in the correct plane, and get them to meet, but the edge will be ragged from grit impact. It will also leave a lot of random stria on the bevel from the loose grit, no uniform stria pattern.

It is an easy fix. Wash the stone, give it a quick refresh lap and do 20 or so lite finish laps on the clean stone. Now you will cut a clean bevel that will leave uniform stria pattern and a straighter edge from the grit bonded to the stone. You should not need a lot of laps if the bevels were ground flat, to the correct angle and meeting.

If you joint the edge straight removing all the rough burr and flashing, then do finish laps you can get an even straighter edge off a 1k or any stone. With a little bit of extra work and light laps you can get a very straight edge from a 1k, which is the goal, a straight edge.

Take a look at Precision Ground Flat Stones, they are synthetic 400 grit capable of leaving a near mirror finish on machined work. The trick is to keep them clean and flat, they do not cut, just polish/deburr.

Natural stone slurry like Jnats are a compilation of grits that are frangible, they will break down into smaller grit, so smoother polish and less impact damage, but start with aggression. If you thin the slurry, it will polish finer and with less edge impact damage.

You can use synthetic slurry to increase stone aggression, set a bevel or remove previous stria, works great with circles, but you must polish out the deep stria they create on a clean slurry free stone and straighten the edge at the same time.

I do a 1to 8k jump frequently, with slurry on both. Just finish on a clean stone. My Fuji 8k will leave a near mirror off a clean stone face and super straight edge. I often use Tsushima slurry on the 8k finish laps, to start a Kasumi finish when I will be finishing on a Jnat. Natural Jnat slurry will break down, unlike synthetic slurry.
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This is why I prefer diamond film to any other abrasive. Diamond is very aggressive but still cuts at the grit size listed, which means big jumps in grit size is not only not a problem but it is still relatively fast. Going from 6 micron to 0.5 micron will quickly and efficiently a razor's edge if the bevel is set. 6 micron diamond film will actually finish setting a questionable bevel (this is going to generate some hate mail.... :eek2:). Diamond also has the advantage of basically not wearing out, at least in a decade of use on my own razors.

CBN is also very aggressive and fast cutting but is not available on film as far as I know. But as a material to charge a substrate such as leather, balsa, nano cloth, etc. it is also excellent and will compete with diamond.

Of course there is nothing wrong with much smaller steps through a larger number of grit sizes. Over the years, I have collected a pretty wide collection of film grit sizes and have used them all. But once going to diamond I simply found the intermediate steps to be unnecessary. If some time is saved in using smaller steps in grit, it is not as much time as swapping all the different films in and out of the sequence.

Just to add: I find a 3 micron to 0.5 micron diamond film sequence is sufficient for any razor that has a bevel set, no matter how dull. Of course that is not useful to repair and edge, hone out chips, etc. but it is a very efficient for any normal razor honing.
Biggest jump I've made was in using a 1.2k/8k King combo stone. In doing this, I found the King synthetic nagura to be very helpful in refreshing the surface of the 1.2k as needed. Edges that resulted, off plain leather stropping, were perfectly serviceable, although they could have been improved by using a finer stone or paste sequence afterwards.

If you search on another thread here, Dictum's recommendation in using the Shapton 7 series with straight razors is actually quite conservative, 6.7 > 3 > 2 > 0.85 microns, or something like 2k > 4k > 6k > 10k JIS depending on what site you visit.

Recently, on another forum, someone resurrected a thread by Neil Miller, wherein he recommended doubling as to stone changes: 1k > 2k > 4k > 8k... I found this interesting as I hadn't heard of it before. I suppose it also is based on synthetic stones, but the binder could affect and change things there as well.

This may be moot with natural stones, which cannot really be assigned a JIS grit rating and may allow more variability as to pressure as applied resulting in a more flexible range to each stone.
Here is a test i did some time ago. This is a Hart steel razor that was honed on shapton GS7 starting at 6.2 (2k), 1.2 (8k), 0.85 (16-17k) followed by a jnat with tomo slurry. I was not intending these photos to be used for anything, so it is just some observations that might be relevant to this discussion.

GS7 2k striation (sorry for the microfiber lint)
shapton 2k.jpg.jpg

GS7 1.2 (8k). Now i found a chip in the edge. The striations from the 2k is more or less gone. The sensible think would be to go back to the 2k, but i wanted to see what happened if i moved to the 0.85 (16-17k). One more "big" jump.
shapton 8k.jpg.jpg

GS7 0.85 micron. Now the chip have become smaller, but the edge is beginning to get more fragile. It is beginning to get a little rougher on some parts of the edge.
shapton 0.85.jpg.jpg

JNAT with light tomo slurry. The chip is now more or less gone. You will not notice this during a shave. More work with another slurry would probably clean up the edge more.
jnat tomo slurry.jpg.jpg

I now inspected the blade and found a small microchip in a different part of the edge. The chip is really small, but it is not a good sign. The last photo will show how little it takes just by doing 10 passes on TI white paste on balsa. This is in my opinion caused by the deeper striations from the 2k that was not visible before. This might have been avoided if i had put in a 4k or a 6k after the 2k. I am not sure, but i do not see this if i use smaller jumps in grit.
JNAT micro chip.jpg.jpg

After 10 passes on TI white paste on balsa and leather stropping the micro chip is still there, but will not be felt during a shave. However, it is a weak spot in the edge that might brake off after a few shaves.
TI paste balsa.jpg.jpg

This does not prove that large grit jumps should be avoided, but i do think it would be wise to put in a 4k or a 6k.
It also shows that a really light slurry on a jnat after 15-20 passes seemed to reduce the chip size quite fast. The slurry seem to remove metal at the apex allot better then the higher grit shapton stones.

So you might get away with larger git jumps if you finish on a natural, but from experience, if i had stayed longer on the 0.85 shapton the edge would start to brake down before the apex gets straight.
Other synthetic stones might yield different results.
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Interesting thread, I have been doing a little bit of experimenting with grit jumps.

Synthetic stones I have are chosera 1k, 2k shapton glass, 5k naniwa, 6k shapton glass hc, 8k naniwa, 12k naniwa, and the gok 20k.

Naturals I have are 5x2 coticule, 8x2 trans ark, nakayama karasu, a small thuri 4.5×2.5 ish and a 7 inch thin coticule.

For razors that are in good condition lately I have been going 6k 8k then 20k. Wondering if I can go from 6k to 20k but probably too big of jump. Skipping the 6k and going to 8k doesn't seem too bad though. Also the 6k 12k and then 20k seems like a good option as well. For natural finishing I can go 6k to coticule and jnat without a problem. For the thuri and ark I prefer coming off the 8k as they are slower.

Naniwa 5k is a stone I don't really need with my set up but I like having it as my knife finisher after the chosera 1k and I don't have to worry about flattening other stones after sharpening the knife.

I am moving this year so I am looking at what I need and don't need. I think I have a good set up though where I can keep knife and straight stones separate. Might be reducing my naturals down to just my coticule while things are hectic then look for a nice jnat when I have more time.
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I honed the razor again and shave tested it today. I ‘killed’ the edge on the stone. Then i used a shapton gs 3k hr followed by a 6k hr. I finished with one dmt slurry and a tomo slurry on the same jnat. I got a much cleaner edge and a really comfortable shave.
I could probably skipped the 3k, but it was previously honed with tape because of chipping issues. I got a cleaner edge even with a more shallow bevel angle.
For some reason my edges are usually better if i include more stones, especially if it is a full synthetic progression.
Usually when i get issues i can trace it back to a deeper scratch from my coarsest stone that show up late in the progression. The sub surface damage to the edge might be bigger then it looks. I think this might be one argument to include additional grits early in the progression or to spend a little extra time on the next stone if the grit jump is large, even of the striation from the coarse stone seem to be erased.
So, first Hart’s are notorious for chipping.

And yes, with a Hart, I would slip in a 4k.

I do believe with some steels deep cuts do/can leave and impact damage that can surface if all the damaged steel is not removed. That impact damage can come from aggressive grinding when the razor was ground on belts, (Ceramic) or from aggressive stones when honing, (Diamonds are notorious).

If a razor is particularly hard, it is not uncommon for the honer to drop down in stone, sub 1k or use more pressure to set a bevel. Once the deep 1k stria is removed, the surrounding steel is still damaged and can chip easily in the following grits if enough steel is not removed. Visually removing a chip is not enough.

I recall when Hart’s were new, several guys sold them after a couple honing, and the new honers reported after a couple more honing, the edge calmed down and stopped chipping.

So, as always, you do what the razor needs. And on some you can not take such large jumps or use pressure.


Ask me about shaving naked!
Wondering if I can go from 6k to 20k but probably too big of jump.

Check out the grits supplied in the Shapton G7 3-stone kit. This is described as a knife system but still, the stones are blazing fast. From Sharpening Supplies:

The three grits are:

  • 25 micron - about 600 grit. This grit is used to efficiently shape an edge on dull knives.
  • 6.70 micron - about 2500 grit. This grit is used to refine an edge shaped on the 25 micron stone, or to refresh the edge on a knife that needs only a light touch up.
  • .44 micron - over 30,000 grit. This grit is even finer than the .49 micron/30,000 grit stone found in the HR series, and we have no other stones so fine. It is used to put the finishing touch on a razor sharp edge.
Yes, I know, it is a “Knife” set but Shapton seems to be saying those grit jumps are ok.

There is also an accomplished YouTube Woodworker/Tool maker that advocates honing tools, (chisels and plane blades) with a 500 grit Shapton or 1k Diamond plate and jump straight to a 16k Shapton to finish, with impressive results, micron shavings and super smooth wood finishes. Yes, again I know, that is for tools, but you can not argue with the results, especially if you actually, try these seemingly crazy jumps.

On knives (and tools) this kind of edge can work very well; I do it all the time, people call it a 'hybrid edge'. Though the theory behind it is a little different from what you want in a razor...

A large jump to achieve a hybrid edge on a knife is to maintain the saw-like finish of a low grit stone while polishing out some of the aggressiveness on a super high grit stone, that would otherwise be ott for kitchen knives in terms of refinement. To hopefully give you a 'best of both worlds' type finish. You spend very little time on the fine stone, it's used almost more as a deburring technique, sometimes at a slightly higher angle for a microbevel.

Something like the SG500 onto a trans ark or other razor finisher gives a pretty extraordinary knife edge, though it can be a little difficult to pull off. The importance of maintaining a completely exact angle when freehanding knives is a little overplayed, but for stuff like this it's very easy to roll/round/generally trash an edge on the fine stone.


I know sod all about how big jumps work for razors. But when you do it on knives and tools it's to achieve something quite different - you're specifically trying to keep some of the character from the lower grit.
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