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View Full Version : Which is finer for use on a strop Flexcut gold or green aluminum oxide powder



allen long
03-23-2011, 11:19 PM
I was wondering which compound is finer for stropping tools - the Flexcut Gold compound or the green (aluminum oxide?) powder?

Jim Koepke
03-24-2011, 2:56 AM
Dr. Google is your friend.

A quick search indicates this from flexcut.com:


As with all polishing compound, that is a hard question to give a definitive answer. Some of the particle sizes go as small as .6 microns, some are much larger. If they were all .6 micron, it would cut much too slowly. Polishing is a very different process than grinding or sanding.

The green compounds that I could find say they have about .5 micron particle size.

Flexcut says there are health issues with using green compounds since they use chrome. The chrome makes the compound a more aggressive compound.

jtk

David Weaver
03-24-2011, 8:33 AM
I think they're chromium oxide. Not all greens are the same. I think the sears green compound is similar to a lot of gold compounds in terms of fineness (at any rate, it can definitely be used and is sometimes on sale for $2 for a stick that would last a while)

The green stuff that LV, woodcraft and rockler sells is finer than the gold flexcut stuff for sure, but it does remove metal a little slower than the flexcut stuff because of it.

I think chromium oxide has health considerations if you're going to have it as airborne dust or eat it. It can also be a skin irritant according to the MSDS. Otherwise in the waxy stuff that it's suspended in, I don't think most people here are ever going to notice any irritation using it - I haven't.

Chromium (III) oxide, which I'm assuming is the material in the green LV stuff, is not a known carcinogen, so I wouldn't get too wound up with what flexcut has said. The health considerations are probably a lot more relevant in a lab or industrial setting where you could be working with the dust and doing all kinds of things to it.

Probably the nicest thing about the green stuff the woodworking stores sell vs. the green buffing compounds you find in a hardware store in general is that the binder is soft enough that you can get it off. On leather or MDF, it does create an exceptionally fine edge in everything I've used it on.

Michael Redmond
03-24-2011, 1:01 PM
Hi, How much green stuff do you put on a strop?
Regards Michael

Tony Zaffuto
03-24-2011, 1:47 PM
If you are using an old barber's strop, you're supposed to use bay rum for the best edge.

george wilson
03-24-2011, 1:51 PM
I never use an excessive amount of compound,and the older and more worn it gets,the sharper it will strop. At least,that's the way I use it.

Jon van der Linden
03-24-2011, 2:02 PM
There is a large range of polishing compounds that are available commercially that are finer than those mentioned here. Some of these are intended for polishing plastics to a high gloss. Randall Rosenthal uses those and a soft cotton wheel to produce a super sharp edge as described in the carving forum here. You can see an example of his results:
http://www.sawmillcreek.org/showthread.php?156860-hush-money-number-eight&
Keep in mind that most compounds are intended for high speed polishing, they just melt onto the wheel. It's considerably more difficult to get them onto a flat strop.

You also don't necessarily need a compound for stropping. As described on several threads here by George Wilson, you can use paper, your hand, all sorts of things. Stropping is a delicate operation and just requires a few touches. In that sense it's quite different from using a stone. With a strop you can dub the edge quite easily which is the opposite of what you're trying to accomplish.

Joe O'Leary
03-24-2011, 2:11 PM
How do you know when to recharge the strop?
Also, I use mineral oil to do this. Is that the best thing?

David Weaver
03-24-2011, 2:20 PM
Hi, How much green stuff do you put on a strop?
Regards Michael

Not that much. It's probably not critical, but first, the strop cuts very well with not much of it at all, and second, I think it's nice to get the edge in contact with leather instead of a thick layer of abrasive.

I didn't strop until I started sharpening razor, so my preference is colored by that. You can move the edge with plain leather, so if you already have a pretty good polish, maybe green stuff isn't even required. If you do want to go with green stuff, draw a pattern of Xs on whatever you're going to strop.

Off a fine stone for regular O1 and A2, i like plain leather. For sharpening tougher steels, i like it with a little green stuff, and even better if it's on something hooked to an electric motor to do the work.

Stropping creates a lot of arguments because a lot of different things work well, and you really can't see what's going on at the edge when you do it, you can only observe the results of using what you sharpened, which could just as easily be affected by a lot of other things.

Tim Put
03-25-2011, 11:17 AM
Most of the green stuff (including the LV, Rockler, etc.) is only part Cr^2O^3. They're largely alumina, and substantially coarser than the advertised 0.5microns.

Jim Koepke
03-25-2011, 12:33 PM
Most of the green stuff (including the LV, Rockler, etc.) is only part Cr^2O^3. They're largely alumina, and substantially coarser than the advertised 0.5microns.

You are most likely correct. That issue is addressed in my quote from Flexcut:


As with all polishing compound, that is a hard question to give a definitive answer. Some of the particle sizes go as small as .6 microns, some are much larger. If they were all .6 micron, it would cut much too slowly. Polishing is a very different process than grinding or sanding.

My question would be how is the grit of a compound determined. Is it by the size of the scratches left in the metal when using a particular compound?

As soon as the compound is being used it will start to break down into smaller particles.

My easy test is to find what compound works best for you and your tools. With all the different metals we have in our shops and the developments in metallurgy we will see in coming years, it wouldn't be surprising to find some compounds work better on some metals and some work better on others.

The original question was:


I was wondering which compound is finer for stropping tools - the Flexcut Gold compound or the green (aluminum oxide?) powder?

A definitive answer may not be possible without a lot of qualifications. What kind of steel is it being used to polish?

What kind of stropping media will it be used with, leather, MDF, steel plate or some other material?

Actually, the best answer might be for Allen to try both and see if one actually fits his needs better than the other.

I can not answer Allen's question since I have not used the Flexcut Gold.
My satisfaction with a green stropping compound could be a matter of not knowing any better. It was a stick of polishing compound that was bought while visiting a lapidary store with my wife. I have no idea of who made the "green stick" or what they claim about its properties.

It puts a nice finish on my blades. It may be a case of blissful ignorance, but until something comes along that works better, the "green stick" works for me.

jtk

Terry Beadle
03-25-2011, 12:42 PM
On page 219 of Ron Hock's The Perfect Edge, he shows a 2000 magnified picture of the two abrasives on a test edge. The green has a less ragged edge than the gold. However, the difference takes every bit of the 2000 magnification to identify and it's debatable as to weather a little more ragged edge cuts better than a smoother one. The pictures show that a 0.1micron honing film puts them both to same.

As far as wood working edge use goes, either one will greatly improve a smoother's edge and edge retention IMO. I'd say, "Which one's cheaper !" as either will do the job that a human can't detect the difference on.

Thanks again to Ron Hock for a great book. His hints really helped in the kitchen knives department too.

Jim Koepke
03-25-2011, 12:50 PM
Thanks again to Ron Hock for a great book. His hints really helped in the kitchen knives department too.

Darn, sounds like I am going to have to spend $40 to get better at sharpening.

jtk

Bob Strawn
03-25-2011, 5:17 PM
Shooting from the hip and quoting memory, I think flexcut is mostly cerium oxide. Cerium Oxide, if my memory is again working, has a nice fracture point at about .3 microns. Nice stuff that. As far as toxicity goes, here is the MSDS for Cerium Oxide. (http://www.sciencelab.com/msds.php?msdsId=9923351) If you read the MSDS 's, Chromium Oxide (http://www.sciencelab.com/xMSDS-Chromium_oxide-9923471) is not especially more scary than Cerium Oxide. Neither one should be bathed in or used to season greens, but a lot of us work with much more dangerous stuff. I would rate cocobolo dust and osage splinters as more dangerous in general. That said, be careful out there, good ventilation, washing hands, and decent lab technique can go a long way towards making things safer.


Bob

allen long
03-27-2011, 10:47 PM
Many thanks to all who have responded. The reason I asked was because I have both compounds. I was going to charge a leather strop with the rougher of the two, and MDF with the finer stuff. Probably overkill. But hey, it's not about using the tools, its about collecting and optimizing them correct? ;) I am going for a hand-sharpened edge that will draw blood when you simply look at a picture of it.

Steve Branam
12-20-2011, 11:39 AM
I tried the Flexcut Gold yesterday while following Chris Pye's carving tool sharpening instructions, having used a green stick for a while. It was one of those holy crap! moments. The gold put a finer edge on, with nearly an instant mirror-polish finish. I pulled out a few chisels I had recently stropped and tried them, and got the same improvement, testing on a scrap of mahogany before and after. The strop looked like it had been drawn on with a metal crayon.

Maybe I just happen to have one of the poorer green sticks, with poor grain size or poor proportion of abrasive to binder, but I'm sold on the gold for a while.

David Weaver
12-20-2011, 12:20 PM
I think the gold cuts more aggressively, and you're likely to spend less time on a strop or a stone surface that's been smeared with it.

If a green stuff is based on what is essentially chromium oxide pigment powder (the stuff that is powder by itself and 0.5 microns) then the green stuff should be multiples finer, but a pure chromium oxide powder will cut slowly enough that you're likely to get a less good result than the gold abrasive waiting for it to get the job done.

The green stuff is magic on razors. And by that, I mean not the "microfine" stick that LV sells, as that has stuff in it that I'm convinced is added to make it go acceptably fast.

Star shaving sells Hand American green chromium oxide powder (pure, as opposed to the sticks that have green and other stuff) and it is clearly finer than the sticks are.

For general use, I would use the flexcut gold or white al-ox sticks instead of green - they cut more aggressively and though the edge won't be quite as fine as it would be if you did perfect work with the green, they are sharp enough for anything woodworking and the fast cut makes it easier to get the edge you want out of them....

.... but they aren't fine enough that I'd change my straight razor strop from hand american green to them.

Shaving with a straight razor is a good way to get much more closely acquainted to the quality and smoothness of an edge than woodworking tools, where a good 3 micron finished edge feels the same on a plane as a 1/2 micron finished edge. Your face will tell you in a hurry if you use a 3 micron finish on a razor with minimal stropping to follow it.

Jim Belair
12-20-2011, 1:14 PM
Shaving with a straight razor is a good way to get much more closely acquainted to the quality and smoothness of an edge

I'll just take your word for it.

Jim B

David Weaver
12-20-2011, 2:00 PM
It's just like hand tools. I thought it would be a novel way to shave once in a while on the weekends, etc.

Now I don't shave any other way. And like hand planes, when you use a straight razor a lot, the initial notion that it's a 10-20 minute process with hot towels and all of this other stuff....nah, it's a couple of minutes for a very good shave - no burn, no clogged razor heads, no "I think this one might be dull, but i'm going to stretch it a little to get my money's worth".

Helps understand sharpening, too, though the sharpening and stropping are to a different level and not necessary for woodworking.