Am I seeing things - a sharpening question.

[Clinton Findlay]

I don't know if there is a more contentious subject than sharpening and the associated "why's" arising from technique.

I have a question though.... hope I don't start any arguments!

A friend sharpened a plane blade (O1 tool steel - thanks St James Bay Tool Co :) ) on his 4000 and 6000 waterstones.
The edge has lasted a lot longer than I would normally expect.
Normally I use scary sharp to 2000.
He didn't do anything that I don't ordinarily do, except for the finer grit.

Has anyone else noticed this?

I think it might be because he polished the back of the blade to a higher degree. :confused:

Does anyone have some thoughts, I'd like to hear a few theories before I bother with a test.
Thanks

[Dave Anderson NH]

There are so many possibilites here it's almost impossible to offer any suggestions. A few possibilites come to mind immediately though.

1. Was the bevel set at a higher angle than normal?

2. Was the wood used for the test a softwood, a hardwood, or a gnarly piece?

3. Is the sharpener particularly adept and practiced at using his particular technique? Has he used it for a long time?

4. Does the sharpener always get this type of result or was this a single serendipitous result?

5. Does the sharpener polish his back significantly better than you do?

All of these questions seem simple, but they might allow you to analyze your own technique and draw some conclusions. The use of high grits alone does not guarantee good results. Technique is developed over time by constant practice and minor adjustments until the desired result is attained.

[Clinton Findlay]

1. No, the bevel was the same, same jig used as well.

2. I'm preparing a large amount of the same timber species. I took the plane to his place, used it, it was sharpened, then used it a lot on a few different species, then back home and on with the original species. The blade is 'lasting' longer on the species I am preparing - much longer than I'd expect from previous experience.

3. He has used his technique for a long time, but basically the only difference is the use of waterstones, where I have stuck with scary sharp for a long time. The use of a jig means the repeatability 'should' be the same?

4. I don't know, although he is very experienced and turns out excellent work.

5. This is what I think might be the major difference, i.e. a polish with 2000 grit is not as fine with 6000.

Basically there is a diffence between the polish achieved on the back of the blade and the 'polish' on the bevel - due to using a finer grit.

I assumed a finer grit would mean the blade ends up sharper.... now that I am seeing the edge hold longer, I'm stumped.
I had thought that a finer grit would produce a sharper edge, but not one that was so significant that I'd bother with buying waterstones.
If using a finer grit means that my edges will stay sharp longer, I'm sold.
I'd like to know why though.

[Steven Wilson]

I find that the edge of my bench chisels last longer and cut easier since I switched from scary sharp to using Shapton stones.

[Doug Ketellapper]

I use Norton water stones for sharpening my planes and chisels. If I need to re-grind a bevel or if I have a chip I need to take out I use my Tormek. Recently I experimented with the sandpaper method, but finishing up on the Norton 4000 then 8000 stones. I've found it more difficult to get all the scratches out from the previous grit when using sandpaper. Also, practically speaking, I find it easier to remove the burr from sharpening on the waterstones. These are just a qualitative observation which has no basis in science, so take it as such. That's the only thing I can think of that has been different for me. Maybe it's because sandpaper dulls, but the waterstones are always exposing new abrasive, and you end up with a mix on a particular stone. Just thinking out loud here. The whole grit thing is confusing for me, sandpaper grits different from stone grits etc. If his 6000 grit stone is indeed finer than your 2000 grit paper, then his edge is going to be sharper and last longer.

[Mark Stutz]

Clinton,
I've never used Scary Sahrp, only waterstones, so I can't comment on any difference. You don't say in your original post, but infer this is a NEW blade. I'm not sure how I see that being sharper to begin with tranlates to edge retention, but "steel" does. Could it be the blade itself?

Mark

[Cliff Polubinsky]

Mark,

I am not an expert, nor do I play one on TV, but if I correctly remember an explanation I read once, a sharper blade can retain an edge longer. The reason is that an edge is never actually smooth. It consists of small ridges and the 'sharper' the edge the smaller the ridges. With use these ridges break off. If they are small enough, what remains is still to some extent small enough to be 'sharp' and will still cut ok. With more use, that is more ridges breaking off, you at some time come to the point where what is left doesn't cut. If you start with a blade not as 'sharp', as in larger ridges, when they break off you come to the point where the blade doesn't cut sooner.

Of course the steel has a great effect on how long the ridges hold out. And maybe the above explanation is just hot air, but it made sense to me at the time.

And off topic, I had a chance to use that scrub a couple of times and it works wonderfully.

Cliff

[Mark Stutz]

Cliff,
That makes sense to me. I've reread Lee's book on sharpening a couple of times, and still learn something new each time! I looked at my other post again...I was in a hurry:o , and wasn't very articulate. My thought was that the longer edge retention of this blade may be all in the blade rather than how it was sharpened. I wasn't sure if it had been sharpened with both methods or not.

[Doug Shepard]

I'm sure it's nothing more than the fact that it's Monday and all the planets are in the correct alignment and your friend was surely wearing his lucky underwear while sharpening (or maybe Tyler's thong?).:D
Just FYI - LV sells some really fine grit stuff that's good for the last few passes of scary sharpening.
http://www.leevalley.com/wood/page.aspx?c=2&p=33004&cat=1,43072

Course if you're not wearing your lucky underwear, nothing's going to help.

[Clinton Findlay]

Hmmm, 5 replies and I'm thinking that there is a bit of a consensus as to "the finer the edge finish the longer it lasts. ??

Mark - The blade has been sharpened quite a few times, about 8 times I think.... its only new in the sense that I waited a long time to find one for the Sargent Auto-set it fits, so I'm still enjoying using the plane. Took me a little more than 12 months to find and get the replacement blade, not wanting to pay big $ for an original.
I had thought that perhaps I had just exposed a harder section of the metal, but it would seem odd/unlikely that from one sharpening I hit a uniform band of a higher hardness ??

Thanks for all the replies, I guess that unless someone comes up with a concrete answer, I'll put it down to a 'maybe' until I decide if I'm bothered doing a test.
Thanks to all.

Just saw the last post(s) - Mark, I knew what you were saying, you weren't that "inarticulate" :p

Cliff - sounds plausible to me.

Doug - lucky underwear...... nah, but it might have been the way he was holding his tongue.

[Maurice Metzger]

I don't think you can do a straight comparison of grit size between 2000 grit sandpaper and a 4000 grit waterstone - the waterstone follows the Japanese (JIS) grit sizing standard, which is different from the CAMI standard used for sandpaper.

I've seen different comparisons between the two. The Lee Valley web site:

http://www.leevalley.com/wood/page.aspx?c=2&p=46224&cat=1,43072

states that a 4000 grit waterstone has a 2 micron particle size, but this web site:

http://users.ameritech.net/knives/grits.htm

puts a 4000 grit waterstone at 3 microns, and shows a 1 micron particle size for 2000 grit under the CAMI standard.

Maurice

[Don Naples]

Most SiC paper in fine grits is usually not CAMI standard abrasive but rather FEPA. A P2000 grit paper is 10.4 micron. At the below link, there is a chart of the grits and on page two shows one of the problems using Scary Sharp to remove any significant amount of metal. You may get the metal to shine, but it may not be as sharp as what you will get using a waterstone that may even show more scratches in the metal surface. See the data on this link. http://www.woodartistry.com/06%20update%20files/Sharpening%20TipsV2.pdf
Sharp tools are more fun to use.
Don

[Mark Singer]

The finer edge has less resistance and heat and partical abrasion...it basically repels better and lasts longer...I go to about 8000 Shapton stone on the fine stuff...

[Dave Anderson NH]

Clinton, While not a certainty, it is possible that you did hit a better section of steel. Often a factory sharpening and shaping of the bevel will overheat the blade or the blade will have been overheated in the last steps of manufacturing and thus draw the hardness out of the tip. After a couple or a few sharpenings you have ground away the softened steel and have reached the fully hardened section. Like I said though, this is not a certainty, but just another possiblility to confuse the issue.

[Clinton Findlay]

Thanks Dave, you really added another variable with your last post. :D I won't discount it as I try to work out "why is it so?"

Mark and Don, thanks - a good theory and the weblink will be handy.

Maurice - I find it confusing when 3 or 4 standards are used, I get an understanding of one standard, and then someone starts talking about things using another.... :rolleyes:

I think I need to:
work out what a "test of sharpness/bluntness" should be,
do a test of 'scary sharp to 2000' versus 'waterstones to 6 or 8 thou',
and find out an answer for myself.

I'm not sure if I really could be bothered doing the test, and for me to spend @ $250 (US$190) on two or three stones requires a lot of justification (to myself).
Not sure if I can overcome my natural miser's instinct, however it is playing on my mind. I really dislike not knowing something, and the extra life of edge is starting to look attractive.

Again, Thanks for all the replies, I appreciate it.

[Pam Niedermayer]

Clinton, one of the things you need to watch out for in using sandpaper for sharpening is inadvertant rounding over of the edge. This happens when the paper moves a bit.

Pam

[Cliff Rohrabacher]

Grit in a stone isn't the same thing as the same grit on a paper. They produce different results. The difference is the depth of cut of the abrasive particles. Paper will produce deeper cuts.

It's my belief that the abrasive paper system will produce an edge that is more like very fine micro-serrations as the grit particles on the paper are very proud of the paper and will make fairly aggressive cuts in the steel being honed.

The serrated edge is plenty sharp and cuts fast and easy however because it's lots of small points doing the work they can round over more quickly than a smother edge. Once that happens it will feel dull.

The edge obtained from a stone will be composed of more finely cut marks from the stone. The grit is only one factor. the stone's grit particles don't sit proud and can't bite as deeply as the grit on paper. The result using stones is a smother more polished surface. This is likely going to be tad less aggressive than the micro serrations form a paper abrasive system but will likely last longer because more of the steel is in contact with the work sharing the load.

Which is better is, I think, a question of pure preference.