Cosman Sharpening Method Thoughts

[Rob Luter]

As promised in this thread, I tried out my new sharpening system and wanted to share my thoughts.

Background: I started with sandpaper on glass about 15 years ago and it's served my well. About 12 years ago I mounted 2 1/2 x 11 glass blocks on MDF and used them as a base for 3M abrasive film. I would cycle through the 5 available grits from 40 micron to .3 micron and wind up with a pretty nice edge. The only complaints I had were the time it took and the durability of the film.

I watched the Rob Cosman video where he goes directly from a 1000 grit Trend Diamond plate to a 16K Grit Shapton and achieves a stupid sharp edge in under a minute. I thought, sure...how can that work? I was down in Indy earlier this year and stopped at Woodcraft to do a little window shopping and the resident sharpening guru was promoting the same system. He gave a demo where he dulled up a plane iron in a big way then put a new edge on it. Darned if it didn't work.

Last week I was at a point where I had to order some more film. Santa determined it was time to take the plunge so he ordered me the same setup Rob Cosman and Woodcraft were promoting, a 300/1000 Trend Diamond Plate and a 16K Shapton.

First off, they work great. Just as promised and just as demonstrated. It takes up far less space too. It is a whole different experience.

The Trend Diamond Plate was very flat right out of the box. I used the 300 grit side to dress a steel plate I have to free up any stray diamond particles that might gough the Shapton Stone during flattening (Cosman recommended). It didn't seem to be an issue. The 1000 grit side establishes a secondary bevel very quickly and with very little pressure

The 16K Shapton cuts amazingly fast for being as fine as it is. By comparison, the .3 micron 3M film doesn't cut at all, it just polishes. I was able to establish a mirror finish tertiary bevel with just a few strokes. I freehanded my chisels and all but one plane iron. My LN jig worked well for that one.

The edge quality I achieved is better than ever. Off the 16K Shapton it was even better than off the strops I've made. The process is very speedy too. Once the dust settles from Christmas I'll likely add an intermediate grit Shapton (4K or 6K) for day to day use and save the Trend Diamond Plate for heavier work and for flattening the Shaptons occasionally.

The whole kit was kind of spendy, but if I look at what I've spent on abrasive film and other supplies over the years I think I'll be money ahead eventually. I sure will save a bunch of time.

[Phil Mueller]

Thanks for the update, Rob. As I said in your other thread, I’ve been eyeing this system as well. A couple questions; did you adopt the lower position (about mid way up Cosman’s bench level), and are you doing the ruler trick at the end?

[Rob Luter]

The top of my sharpening station is actually 37” off the floor. I’d like it a little lower but it’s a salvaged metal table made of welded steel tubing. Cutting it down would be a nightmare. After 12 years I’m used to it. Maybe some day.

I always use the ruler trick. I use it to prep a new blade as well as to knock off the burr after sharpening. It works great, and especially well with the new Shapton.

[Ray Newman]

Just finished watching Cosman sharpen a plane blade using his method. results were impressive. What I wonder is just how long the Shapton 16000 stone will last will all the required flatening using the 300 grit diamond stone/plate.

[Tim Andrews]

Rob, thanks for posting your experiences. I’m just getting into my woodworking season now that golf season is over, and I spent several hours today getting my chisels and planes touched up and ready for work after their summer vacation.

I also use the 3M films on glass plates, and I agree that the very fine films only seem to polish, not much different than the strop I use for my final step. I’ve been considering purchasing the same setup that you got, and your review has me leaning more that way. It seems that it’s much more efficient.

Now, if I can only wean myself off my sharpening jig and train my body to keep a consistent angle with freehand sharpening, it will make the process much faster.

Did you also get the holders for the stones to keep them from moving around?

[Rob Luter]

Just finished watching Cosman sharpen a plane blade using his method. results were impressive. What I wonder is just how long the Shapton 16000 stone will last will all the required flattening using the 300 grit diamond stone/plate.

That was a concern of mine as well. I'm guessing since he sells these and likely gets a deep discount, it's not a concern of his. What I found was that after refreshing the edge on six chisels and four plane irons the stone was still flat as new. I still hit it with the diamond plate briefly but basically just to verify flatness. I have read (on the internet so you know it's true) that the Shaptons wear extremely slowly. The guy that did the demo for me at Woodcraft said he's had his for years and sharpened thousands of edges on it during clinics and such. HE trued it up with the Trend plate frequently. There was well over half of it left. I'm thinking that a hobbiest myself will likely never need to replace it. This will certainly be the case when I add an intermediate grit stone to help share the load.

Rob, thanks for posting your experiences. I’m just getting into my woodworking season now that golf season is over, and I spent several hours today getting my chisels and planes touched up and ready for work after their summer vacation.

I also use the 3M films on glass plates, and I agree that the very fine films only seem to polish, not much different than the strop I use for my final step. I’ve been considering purchasing the same setup that you got, and your review has me leaning more that way. It seems that it’s much more efficient.

Now, if I can only wean myself off my sharpening jig and train my body to keep a consistent angle with freehand sharpening, it will make the process much faster.

Did you also get the holders for the stones to keep them from moving around?

I use a hybrid mix of sharpening jig and freehand. If I need to create a new primary bevel or do any sort of heavy material removal I use a jig. Since I use that bevel as a reference during freehanding I want it accurate. Refreshing the cutting edge can be done freehand without too much trouble. Getting the angle locked in just takes a little practice. I didn't bother with a stone holder. I have a non-skid rubber mesh mat I sit the stones on. It's basically shelf liner.

[Ray Newman]

Rob Luter: thanks for the response about wear to the Shapton!

[Will Blick]

I use the same Shapton stones...
one or two plane blades my stone is never flat....or any stone...
when I scribble a pencil all over the stone, then flatten it,
its incredible how the pencil removal areas demonstrates how the stone is NOT flat...
takes 5-10 several strokes with the flattening stone to remove all pencil marks...
then the flattening stone every 10 uses, I put on a granite flat surface with sand paper, and that needs to be re flattened...
the diamond flatenning stones for the higher grit sharpening stones of course stay flat longer.
Its become so routine now, I dont even think about it...
I tried the jump from 1K to 16K, and never get an edge as good as stepping through the grits...
YMMV

[Warren Mickley]

I tried the jump from 1K to 16K, and never get an edge as good as stepping through the grits...
YMMV

Cosman says he raises the iron 1 or 2 degrees from the 1K to the 16K. It is more than that; he finishes up at or above 40 degrees. You might be getting a better edge.

[Will Blick]

When this is looked at under an electron microscope, its very time consuming to get a 16K stone to remove 1k scratch marks, which makes perfect sense.
Although I do understand what u are saying about raising the angle so u are shooting for a super micro fine beveled edge. A lot easier if you free hand, I use a jig, so not unlimited angles without repositioning....

[Rob Luter]

I tried the jump from 1K to 16K, and never get an edge as good as stepping through the grits... YMMV

Cosman says he raises the iron 1 or 2 degrees from the 1K to the 16K. It is more than that; he finishes up at or above 40 degrees. You might be getting a better edge.

Agreed on both counts. After a week or so of trials I'll say this method screams for an intermediate grit if there has been any significant material removal on the 1000 grit diamond plate. If all you're creating is a tiny tertiary bevel the 16K stone is OK. Much more than that and getting rid of the scratches is too big a job.

I refreshed the edge of my Shooting Plane Iron today. It's PM-V11 steel and had some small chips in the edge. I worked the secondary bevel back with the 1000 grit plate and ridding it of all the scratches with the 16K wasn't going to happen. I was able to create a mirror smooth tertiary bevel though. A few strokes on the strop and it was razor sharp.

I'm certain I'll be investing in a 4K or 6K stone after the holidays.

[Gary Focht]

I refreshed the edge of my Shooting Plane Iron today. It's PM-V11 steel and had some small chips in the edge. I worked the secondary bevel back with the 1000 grit plate and ridding it of all the scratches with the 16K wasn't going to happen. I was able to create a mirror smooth tertiary bevel though. A few strokes on the strop and it was razor sharp.

I'm certain I'll be investing in a 4K or 6K stone after the holidays.

I haven’t looked at the Cosman method recently, but I don’t think he tries to get rid of all the 1000 grit scratches. He is only concerned about the very small tertiary bevel - which you said the 16k stone did well. So it sounds like you can reproduce his method well.

Why do you need the intermediate stone?

[Rob Luter]

For maintaining the secondary bevel. The 1000 grit stone takes off more steel than I need and creates scratches that the 16k has to work hard to remove. A 4000 grit stone will be a better fit for regular touch ups. I’ll break out the 1000 to completely renew the secondary.

[Will Blick]

I would think Robs jump would be more sensible...
or even 8k/16k for touch ups...
seems there is no shortcuts with sharpening
if you short circuit the process, u end up with a less sharp blade vs. going through the grits...
but sometimes, that is all that is required!

[David Glauser]

Rob has a video showing what he does with a new blade. There, he does work up through more grits/ IIRC between the 1000 and the 16000 he hit 4, 8 and 10, or something like that. At any rate, he says it takes a while for a new blade, then the 1000 to 16K touch up is all he needs thereafter.