Thread: Chasing fine sharpening

I was reading though this thread, and while I am okay with the gear I have for sharpening felt sections, it occurred me that David's diamond impregated wood might be useful for sharpening challenging items - ie curved, small stuff, hard access faces. I was shaping timber and glueing 3m paper ./ coating polishing compound to sharpen these surfaces, but the diamonds may be faster.


Thanks

oops...dropped this post in the wrong bin. moved to the stanley 5 thread

I think there's more benefit to doing the final polish/hone by hand on a slightly softer substrate than on a dedicated diamond plate. That ever so slight imperfection and rounding produced makes a gigantically longer lasting edge, where the very hard substrate can sometimes stress or chip the super fine apex.

I also have this strong suspicion that one of the major causes of early edge failure is wire/feather edges. I think the softer substrate helps remove the wire edges without damaging the underlying apex by tearing them off or grinding them back against the apex. The thing is, the super fine polishing grit is too fine to change the underlying bulk geometry. It's not going to round over the entire bevel and create an extra-thick tool that's only useful for chopping.

So for example, it slightly convexes the actual apex without changing the thickness of the edge 0.020" behind the apex. That's important when we're talking about being able to control the durability vs ease of cut for different uses. So for example, I can bulk sharpen at 17 or 20 for light paring cuts, but the edge doesn't fall off. Or I can grind at 30 or 35 for heavy malleting so the chisel doesn't just nail deep into the wood or deform the whole bevel.

Honestly, buffing really helped separate the issues of apex vs bevel.

Originally Posted by truckjohn

I think there's more benefit to doing the final polish/hone by hand on a slightly softer substrate than on a dedicated diamond plate. That ever so slight imperfection and rounding produced makes a gigantically longer lasting edge, where the very hard substrate can sometimes stress or chip the super fine apex.

I also have this strong suspicion that one of the major causes of early edge failure is wire/feather edges. I think the softer substrate helps remove the wire edges without damaging the underlying apex by tearing them off or grinding them back against the apex. The thing is, the super fine polishing grit is too fine to change the underlying bulk geometry. It's not going to round over the entire bevel and create an extra-thick tool that's only useful for chopping.

So for example, it slightly convexes the actual apex without changing the thickness of the edge 0.020" behind the apex. That's important when we're talking about being able to control the durability vs ease of cut for different uses. So for example, I can bulk sharpen at 17 or 20 for light paring cuts, but the edge doesn't fall off. Or I can grind at 30 or 35 for heavy malleting so the chisel doesn't just nail deep into the wood or deform the whole bevel.

Honestly, buffing really helped separate the issues of apex vs bevel.

I agree with every bit of that!

Originally Posted by truckjohn

I think there's more benefit to doing the final polish/hone by hand on a slightly softer substrate than on a dedicated diamond plate. That ever so slight imperfection and rounding produced makes a gigantically longer lasting edge, where the very hard substrate can sometimes stress or chip the super fine apex.

I also have this strong suspicion that one of the major causes of early edge failure is wire/feather edges. I think the softer substrate helps remove the wire edges without damaging the underlying apex by tearing them off or grinding them back against the apex. The thing is, the super fine polishing grit is too fine to change the underlying bulk geometry. It's not going to round over the entire bevel and create an extra-thick tool that's only useful for chopping.

So for example, it slightly convexes the actual apex without changing the thickness of the edge 0.020" behind the apex. That's important when we're talking about being able to control the durability vs ease of cut for different uses. So for example, I can bulk sharpen at 17 or 20 for light paring cuts, but the edge doesn't fall off. Or I can grind at 30 or 35 for heavy malleting so the chisel doesn't just nail deep into the wood or deform the whole bevel.

Honestly, buffing really helped separate the issues of apex vs bevel.

I think you have just answered a question I have had regarding using a soft(Timber leather) substrate perfectly.

Now that all makes perfect sense too this simpleton.

Cheers Matt.

here's a decent substrate comparison - MDF is pretty soft. the cheap metal bonding grade 1-3 micron diamond bag that i got does this to steel when used on MDF.

https://i.imgur.com/Nad40kj.jpg

here is what the same bonding grade material does on a Zapote (pretty hard stuff, not world record, but hard, dense and very stiff):
https://i.imgur.com/PqCGuQi.jpg

here's the zapote - it's in the ballpark of gabon ebony and density is > water by a little. More importantly here, it's smooth and can be planed flat easily.
https://i.imgur.com/jYkgy8m.jpg

I like the zapote better, but it would depend really on what you find in use. The difference in polish is pretty meaningless - 1-3 micron stuff gets this polish pretty quickly, like faster than the sp13k (which is a good stone, but it's fine and a bit soft). Settling junk could be a problem on this (dust, especially metal dust in my shop), but keeping something like this clean takes nothing more than laying a paper towel over it, and you can scrape the surface if needed, several times, before you have any level issues.

as per the rounding discussion above - you can see that the MDF rounds the apex a little more, and so does autosol on MDF:
https://i.imgur.com/ONX5Kqz.jpg (apologies for the dirt on the edge - it's not that easy to get the edge clean enough to have "no nothing" on it. Even when you get it clean, you can still have fibers from jeans or a rag or whatever).

There is a slight difference in initial blistering sharpness for something like this vs. submicron diamond really crisply done on a hard surface, but this is probably more practical for day to day planing when nicks are a bigger threat to quality.

In this discussion with diamonds vs. autosol, it's important to note that if you get steel with vanadium carbides, autosol won't cut them. The diamonds will. I can't remember where I got the bonding grade diamonds, but i like the fact that they're 100 grams for something like $13, so I don't have the urge to be cheap with them like I do little vials. if I set up a data trail, as mentioned above, the number of vials and bags lost or dropped or accidentally dumped is far far above the number ever consumed.

By the way, feel wise with these things, what do I like? the Zapote feels great. it feels almost like a stone and the edge doesn't get into it very easily like it can with softwoods of you're working the back and accidentally skim a little bit of wood off slicing accidentally while polishing.

if you want blinding blinding polish for something, though (like for appearance on a knife bevel), softwood is definitely good for that.

Probably the only academic dispute I could make with MDF is that it's got a ton of included grit.

That said, it's probably not that big of a real life problem seeing that all sorts of people use it.

It's also cheap and extremely uniform. Those are very good qualities for a substrate.

Originally Posted by truckjohn

Probably the only academic dispute I could make with MDF is that it's got a ton of included grit.

That said, it's probably not that big of a real life problem seeing that all sorts of people use it.

It's also cheap and extremely uniform. Those are very good qualities for a substrate.

yeah, haven't found anything in it yet ever that's scratched an edge. I have seen a bit of metal in junky stuff here or there, but all of my "sharpening MDF" has come from two scrap panels that were clean.

it has a little more give than I'd like - the effect is a bright edge, but it's rounded like the autosol picture. I like a little more control than that, but it still works well and has good toughness. Definitely much better for this than a big leather strop - again with the exception of perhaps a hardwood strop and horse leather.

My diamond grit has arrived, earlier than suggested. But I feel like I have done something "dodgy". See photo below. I am yet to use it but will do so on some Spotted Gum - should be hard enough!

Sent from my SM-G986B using Tapatalk

Originally Posted by Mountain Ash

My diamond grit has arrived, earlier than suggested. But I feel like I have done something "dodgy". See photo below. I am yet to use it but will do so on some Spotted Gum - should be hard enough!

Sent from my SM-G986B using Tapatalk

As long as you have no new fresh $50/100 dollar bills lying around, I don’t snort any issues.
As you were, hanging out for a full report.

Cheers Matt.

An just keep an Eye out for Black Mercedes Vans blacked out with “Dude’s” parked out the front.

Hi David, in what situation would you hone with the diamond paste on the flat wooden surface as the final step, rather than buff on the cloth wheel as per unicorn method? Cheers, Zac.

Originally Posted by Fergiz01

Hi David, in what situation would you hone with the diamond paste on the flat wooden surface as the final step, rather than buff on the cloth wheel as per unicorn method? Cheers, Zac.

I would typically buff just about everything here after a work-over on a penultimate stone (like something 3k grit or a less than ultrafine arkansas stone). But I'd say two cases for the diamond stones:

1) something like 10V with a lot of vanadium carbides. You'll be able to plane with it if not using diamonds, but it's missing a lot of what it could be at the start, and you'll be able to feel it. Diamonds will cut right through vanadium carbides like they're plowing a furrow in dirt.

2) you don't like the buffer- some people definitely don't. then working the last of the bevel over with diamonds on a substrate is certainly viable and it doesn't leave much of a burr to deal with.

3) you're chasing sharpness for some other reason:

For calibration of what kind of sharpness you can get, here is a plane iron made of 1095, figure O1 would look about the same.

https://i.imgur.com/nkFRFve.jpg

here is a plane iron sharpened on a slurried 8000 grit waterstone for comparison:
https://i.imgur.com/vyk9GHp.jpg

And a shapton cream (12000) stone. The shapton is aggressive and there are definitely coarse particles in the mix compared to the 12000 grit rating.
https://i.imgur.com/86XdNqK.jpg

Note the neatness of the edge - it's hard to contend the buffer leaves anything dull. Important in this, I think, for day to day sharpening. Buffing is more of a step up in the edge on a plane iron and less of the kind of big roundover on a tiny scale like it is on a chisel.

With that in mind, you can find slightly higher levels of sharpness (like planing competition type edge chasing) by freehanding on diamond on wood ...probably.

Sharpening with the buffer finish is always super fast, and the result is hard to complain about. A minute for the cycle with a plane iron and less probably with a chisel.

Hi All

I also brought my 100 karats of diamond. Slightly coarser than MA's at 2.5 micron.

Set a an MDF disk in my drill press. Initially the disk was a tad unbalanced - used the press as lath and ground a bit to balance the wheel. Not perfect balance, but the press is long way from a 1 tonne cast iron milling machine. Then, spread oil on the disc and rubbed in the diamond dust. Used a tiny fraction of the diamond.

Results - at speed, polished up some edges quickly. Maybe 15 seconds. Gave the backside a polish as well.
Edge produced seems sharp. Sharper than a buffed edge but this assessment is subjective.

Sharpened a plane this way. Performed well.
May do some comparisons between buffed edges (assumed tougher) and fresh sharp edges when there is tearout present on the wood. But results will (again) be subjective.

Regards