Basic Stropping Question

[Patrick Chase]

After stumbling across Brent Beach's site on sharpening, I thought, 'dang, all this stropping business is a waste of time'. This was particularly disheartening because I had just got some really nice leather from Tandy for strops, and some Diamond paste. Total bummer.

I wouldn't take Brent's site as Gospel, not even close. Lots of people get great bottom-line results with sharpening media/systems that he disparages. Also, analyzing edge quality with that little cheapo USB microscope he used is the equivalent of doing photography through the unpolished bottom of a dirty Coke bottle. There's really no telling what he's actually seeing, and IMO he over-interprets murky/inconclusive results quite a bit. I have a far better setup than he did, but even so I don't use it for edge evaluations as it simply can't "see" on a small enough scale to draw meaningful conclusions.

Plenty of people have done tests with SEMs (which CAN see the required level of detail) and obtained rather different results than Brent. See for example some of the stropping results at scienceofsharp.wordpress.com or in Leonard Lee's Sharpening book. I tend to trust the SEM shots over the guy with a Cracker Jack Box microscope and obvious biases...

In terms of measuring actual results (the cutting performance of the edge) I think that Steve Elliott does a good job. Note that he relies quite a bit on diamond pastes (though on cast-iron laps rather than strops) and gets excellent results.

Even if Brent's data were valid IIRC most of his stropping results were with "green compound", which is known to contain a significant percentage of coarse Alumina particles. If you bought good quality diamond paste then his results don't really apply at all to you.

[Warren Mickley]

There are certainly respondents to this thread who are head and shoulders above Brent Beach in experience, discernment and knowledge. Sharpening is an art; stropping is an art. A technician's mentality is not going to yield optimum results. Many scientists and engineers underestimate the complexity of sharpening and the importance of technique.

John Jordan mentioned turning. It is counterintuitive that a polished edge does not yield a better surface. It is also wrong. For old fashioned 20th century work, you want to sand anyway, so the surface doesn't much matter. For high quality turning, crisp and clean, you want a polished edge. The quality of the edge dictates the quality of the surface, whether you are talking rosewood or white pine.

[John K Jordan]

John Jordan mentioned turning. It is counterintuitive that a polished edge does not yield a better surface. It is also wrong....

You are correct, that is wrong. However you may have misinterpreted what I wrote or at least what I thought I wrote. Perhaps I wasn't clear. To be clear a polished edge absolutely leaves a far better surface. That's exactly what I use on my spindle gouges - they will leave an almost polished surface requiring little or no sanding. A rough, serrated edge absolutely transfers those marks to the wood.

However, the rough, serrated edge apparently makes little difference for certain types of turning, such has turning green wood quickly such as when hollowing out bowls. In fact, there are those who say the serrated edge actually cuts better. Many turners sharpen their tools with 180 grit CBN wheels, some use 80 grit AlOx wheels. There is even collective "wisdom" that the wire edge burr from the grinding wheel is desirable for some uses, going back to the grinder every few minutes to raise a new burr. Note that most bowl turners use power sanding and most start with coarse grits so lines from the gouge makes no difference. 80 or 100 grit is a common starting point, sometimes out of habit I suspect or to remove uneven tool marks. However much finer grit will remove the scratches from the gouge itself.

I prefer to work differently, sharpening on either a 600 or 1200 grit wheel then honing at least some on the Tormek leather wheel. From what I hear from others this is almost unheard of. Where a burr is needed on a scraper I first hone then burnish a burr with a carbide rod just like sharpening a cabinet scraper. I remove tool marks or ripples on bowls and platters with hand scrapers if needed and rarely have to start with coarser than 3200 or 220 paper. On small work in fine grained wood I often start with 600 or start and finish with 800 paper and sometimes no sandpaper. There is a definite difference in the smoothness of the turned surface with honed/polished/stropped edges. I learned this from the Tormek literature maybe 15 years ago.

Some of the better woodturning craftsmen I know work the same way as I do - polished edges, fine tool control, very little sanding.

JKJ

[Patrick Chase]

There are certainly respondents to this thread who are head and shoulders above Brent Beach in experience, discernment and knowledge. Sharpening is an art; stropping is an art. A technician's mentality is not going to yield optimum results. Many scientists and engineers underestimate the complexity of sharpening and the importance of technique.

I completely agree with you in substance, though I think you've misdiagnosed the cause of faulty analyses like Brent's.

Technique is indeed critical because none of us have the time/resources to self-evaluate using a scanning electron microscope (SEM). The optical microscopes that many of us do have access to are fundamentally limited by diffraction to scales that are too large to accurately predict edge behavior. We therefore have to rely on consistent, well-practiced technique and evaluation of end results (i.e. how does the edge cut) to ensure that we consistently obtain results that we're incapable of directly observing. That's what I meant when I said in a post a while back that sharpening is one of those things like golf, where you can always improve.

With that said, there is no magic to how a cutting edge is formed and behaves, even if it's very difficult to directly observe. I therefore think that analytical techniques like SEM shots have a lot of power to help us understand the potential of and differences between different media and techniques even if they can't directly guide our day-to-day work. I think that Steve Elliott's efforts to measure and understand the cutting ability of edges in various states of preparation and wear are also a meaningful contribution, and demonstrate how to get useful objective information without a SEM, via result-oriented measurements.

I think it's noteworthy that the people who've gone to the trouble of sufficiently deep analysis (Leonard Lee, Elliott, etc) would be among the last to trivialize the degree of technique involved. I suspect that each of them went through much iteration and many false starts to get to the results they published, and came away with a deep respect for the role of technique, assuming they didn't already have such to begin with.

I guess what I'm saying is that the "real scientists" (the ones who've taken their work far enough to get to a real understanding) agree with you to a greater extent than you seem to credit. The problem here is with folks who've done half-a**ed analyses and yet lay claim to deep "scientific" understanding. I would put Brent Beach solidly in the latter camp.

[Ted Reischl]

I have switched from using leather to using a piece of paperboard. My favorite is the stuff they make cereal boxes out of.

If I were to use leather again, it would not be the typical thick stuff that is glued on to a board but rather the thinnest stuff I could find.

It seems to me, and I am sure someone will correct me if I am wrong, but the role of the leather is carry the compound. If the leather can give, and it will, it is no longer co-planar with the bevel. It may produce a slightly rounded "micro bevel". Using something dense like paperboard would help eliminate that. Or, as someone mentioned above, using a cast iron lap plate.

I have only been doing this a short time on my carving tools and it seems to be giving me a better, longer lasting edge. But that could also be my imagination.

Something to think about and try, cereal boxes are cheap!

[Patrick Chase]

I have switched from using leather to using a piece of paperboard. My favorite is the stuff they make cereal boxes out of.

If I were to use leather again, it would not be the typical thick stuff that is glued on to a board but rather the thinnest stuff I could find.

It seems to me, and I am sure someone will correct me if I am wrong, but the role of the leather is carry the compound. If the leather can give, and it will, it is no longer co-planar with the bevel. It may produce a slightly rounded "micro bevel". Using something dense like paperboard would help eliminate that. Or, as someone mentioned above, using a cast iron lap plate.

People use "stropping compounds" on everything from buffing wheels to cast iron laps, though note that neither of those extremes are really "stropping". It's basically a tradeoff between ease of working the edge and precise control over the tool's edge geometry.

A soft surface will "give" a bit and thereby do its work all the way out to the edge even if you don't hone at exactly the right angle, and even if the edge isn't straight. That's handy if you're trying to quickly touch an edge up on a carving tool, but as you say it may ultimately round the edge over a bit, depending on how you use it. I would also note that if you're using a "naked" (no compound) leather strop to remove the wire edge after polishing then that isn't much of an issue. IIRC that's how Warren uses his, and you really can't argue with his results.

A harder surface will demand better control of honing angle, but in return it will have less tendency to round the edge. I sometimes use compounds on cast iron laps for polishing (NOT wire-edge removal and not really stropping) and in my experience they leave extremely "crisp" bevel geometries. A lot of people find Maple or sometimes MDF to be a reasonable compromise.

Another benefit of a softer surface is that they're more forgiving of larger "rogue" abrasive particles, because such particles will tend to become embedded more deeply in the substrate such that their tips don't stick out. As we've discussed in other sharpening threads that may be why people have good luck with the green compound on leather despite the fact that it's known to contain pretty large alumina particles. In contrast, if you somehow end up with a rogue particle stuck on your cast iron lap, then it WILL leave scratches all over your tools until you get rid of it.

The one concern I would have about using cereal-box cardboard is that cheap bulk cardboard like that often contains a lot of abrasive particles, some of which may be larger/coarser than what you'd use for polishing or stropping a woodworking tool. I don't have a sense as to whether it has enough compliance to be forgiving of that the way leather is.

[David Ragan]

I'm finally going to ask-whats the deal w the cast iron lapping/honing/stropping plates?

Only ones I could find on a search are the pricey ones AKA truing plates, so forth.

And, in regards to wood-will just about any type do?

[steven c newman]

Sellers just uses a pine 4x4 in his vise....

[Patrick Chase]

I'm finally going to ask-whats the deal w the cast iron lapping/honing/stropping plates?

Only ones I could find on a search are the pricey ones AKA truing plates, so forth.

First a disclaimer: Anything that you would do with an iron plate should not properly be described as "stopping". Such plates are used for lapping and polishing, though admittedly a lot of folks blur the line between polishing and stropping by using polishing compounds on their strops.

Purpose-built cast-iron lapping plates are not cheap, at $100 and up from reputable sources. The ones I have are from McMaster Carr. You can also buy high-quality cast iron plates and have them precision ground (which I've also done), but you won't come out financially ahead that way unless you can get the machining done at below-market cost, for example by friends/family. Mild steel plates like the ones LV sells are a lower-cost alternative, and I also use those as I can't afford to dedicate cast iron laps for each of the abrasive grades I use.

Diamond paste in general has a few advantages:

1. Diamond abrasives can sharpen all tools that woodworkers use, including ones made from exotic steels and solid carbide.
2. Diamond is also the "fastest" abrasive for most uses, and typically by a significant margin. Diamond pastes further reinforce this advantage by allowing us to frequently start over with fresh, un-dulled abrasive.
3. Diamond paste has decent long-term economics. You use just a tiny bit for each sharpening session, such that fairly small quantities last a very long time. It's more expensive in the long run than Arks, ceramics, or even waterstones, but in my experience it's cheaper than diamond plates/films or conventional sandpaper.

Cast iron has a few specific advantages as a substrate for diamond paste:

1. Iron is soft enough to "hold" abrasive particles in place and thereby lap harder tool steel without being worn down itself. This may seem counter-intuitive, but softer materials tend to preferentially lap harder ones for this reason. Iron both works faster and wears more slowly than mild steel.
2. Iron is also hard enough that the abrasive particles stay on the surface and continue to cut efficiently for a long time, instead of receding into the lapping surface as with wood, MDF, leather, cardboard, etc. My experience with diamond on softer substrates has been that they stop cutting long before the diamonds wear out, and that's not an economical way to use diamond. IMO they're better matched to cheaper and shorter-lived abrasives like aluminum-oxide and chromium-oxide.
3. Iron also doesn't deform as a result of either pressure or wetting. Leather has a lot of "give", and both leather and wood are poor choices with water-based compounds for obvious reasons.
4. If processed properly Iron laps don't contain harder abrasive particles of their own that would scratch the tool, such as carbides. The cheaper alternative to cast iron is a mild steel like 1018, but I've had some bad experiences with "rogue carbides" when using abrasives smaller than ~3 um (above that the abrasive is larger than any such rogue particle so it's a nonissue).
5. Cast Iron laps are dimensionally stable (again if processed correctly) and can therefore be and remain very flat. My 5x3 iron laps from McMaster were all within ~0.0002" of planar as received (i.e. much better than their spec). This is helpful when transitioning from one grit/plate to another - if the plates aren't flat then it can take a lot of work to get the second grit to cut across the entire surface of the tool.

[steven c newman]

Here is a little something to chew over..

That plane I picked the other day. 1st quarter of 1937 iron. I ground a better bevel and flattened the back. About 5 minutes on a Medium India 600 grit oil stone, then into the plane....

Today I was using that same plane and iron, to plane a bit of Cherry...
good face.jpg
Made quite a few shavings..
shavings.jpg
With most of them like this one..
thin shaving.jpg
Iron does have a slight camber. Maybe when I get a little more time,I can get the edge sharp?

[Patrick Chase]

Iron does have a slight camber. Maybe when I get a little more time,I can get the edge sharp?

Your implied point is of course right on the money: The 80/20 rule (the first 80% of the benefit comes from the first 20% of the effort) applies to woodworking as it does to many other pursuits. Much of what we (and specifically I) have been diving into in this thread is obsessive overkill. What can I say, it's a compulsion.

If you think this is bad you should have seen my ski preparation regime back when I was racing a lot.

Glad to hear you're OK and back home - your first post in that other thread was concerning to say the least!

[David Ragan]

Steven-excellent shavings! I am jealous, sitting here w my bum knee, staring @ my tools some more.

Patrick-thanks so much for the treatise on cast iron plates, etc.

Now, even tho I have no $ on account of our 25th anniversary is the 12th.

McMaster Carr? When they say the tolerance on a bar's thickness is such and such, they dont mean flatness, do they?

If the urge ever overcame me to get some low-carbon steel lapping plates, seems like the economical thing to do is to get the stuff from MC, and let my friend machine it down.

I've gone and looked at the prices-you do save a lot by getting MC stuff and machining.

LV has them for not a huge amount, but about 2-3x as much as MC.

All things considered, I'd probably go for the less hassle factor, and get the LV ones.

[David Bassett]

... If the urge ever overcame me to get some low-carbon steel lapping plates, seems like the economical thing to do is to get the stuff from MC, and let my friend machine it down....

Before you make this your plan have a serious talk with your friend about his machining tolerances....

[Patrick Chase]

Before you make this your plan have a serious talk with your friend about his machining tolerances....

Indeed, though it depends on what grades of paste you want to use.

The largest commonly available grades are 45-60 microns (250# or so). The next grade after those is typically 15 um or so (1000#), so those 2 lapping plates can differ by, say, 1/4 mil (~6 um) across the 2" width of a plane iron without requiring undue work to get the finer abrasive to uniformly remove the scratches from the coarse one. The Veritas plates are spec'ed flat to 2 mils across the full 3x8 surface, with basically all of the error coming in the form of gradual, probably due to thermally-induced warp during machining. Most of them are also better than spec, so those plates are easily good to within 1/4 mil across any given ~2" wide section.

OTOH the finest grades that I routinely use are 3 microns followed by 0.5 microns. Those two plates have to be absolutely dead on, or else you'll end up working for ages to get the 0.5 um paste to cut uniformly across the tool. In my experience the Veritas plates have to be lapped (and lapped, and lapped some more) to work well for abrasives that fine. In contrast the McMaster 5x3 iron plates require very little work - just a bit of lapping to "knock down" the as-ground surface profile, and then scrubbing with brass brushes, scotch-brite, and finally TexWipes to get rid of residual abrasive contamination.

But really, Steven is right. All of this is obsessive overkill for routine honing of common tools (not carbide or terribly exotic alloys). Do as I say, not as I've done.

EDIT: If you find yourself idly pricing out Biax machines on EBay because you want to get metal surfaces (not just laps) very flat much faster than you can by lapping, then you've taken it waaaay too far. It happened to this friend of mine you see. Yeah, a friend, that's the ticket. Of course the blades on those things are carbide, so that further reinforces the requirement for diamond paste on laps. It's what you might call a "virtuous cycle".

[Arvind Srivaths]

From the science of sharp site you quoted:
https://scienceofsharp.com/2015/03/3...-strop-part-3/
This observation provides further evidence that the foil edge burrs produced by the latigo strop are a result of the geometry transition from triangular to micro-convex. Very fine, flexible burrs can be difficult to remove without sacrificing keenness, so avoiding burr formation is always preferable. One effective approach is to first micro-convex the apex with a more aggressive strop, with fabric and coarser abrasives for example.

In the interest of science, after your 10K bench stones, if you could try a denim strop with a 10 micron AlOx paste and then the diamond paste on leather, and see if that results in a better edge, it would be useful to know.

Also, in the same site, he shows that the micro-convex shape caused by leather only changes the angle by a very small value - it trades off better keenness at the edge for less sharpness 3 um from the tip. So the whole use of a hard backing surface is hard to justify.

Thanks,

Arvind