Sharpening with Diamond Lapping Film
Almost every system for sharpening tools works just fine, so the differences between the systems come down to speed, expense, portability and mess.
In December, Lee Valley Tools started carrying diamond lapping film for sharpening edge tools. I kind of ignored it as I was busting my hump building a Campaign Secretary under a tight deadline. But that project (and story) are now done. And after talking to some Lee Valley engineers about the stuff, I bought some lapping film during the Lee Valley free shipping promotion.
The Lee Valley engineers were blown away by the sheer speed of the abrasive. I was intrigued by the portability and low mess factor. The real question in my mind right now is the expense, but more on that later.
The diamond film is a monocrystalline abrasive embedded in a plastic-like film with a PSA backing – it’s peel-and-stick stuff. There are four grits in the set – 15 micron, 3 micron, .5 micron and .1 micron. Yes, point-one micron. The set is $22.50.
The 15 micron is for the primary bevel. The 3 micron is for the secondary bevel. The other two grits polish the secondary bevel.
I stuck the 3” x 6” sheets to small scraps of glass I bought from the hardware store ($2 total — always ask for scraps). The glass worked fine, but I really don’t want to travel with sheets of glass. If I travel with this stuff in the future, I’m going to stick it to Lexan, milled aluminum or scraps of solid surface material, such as Corian.
The difficult part of sticking down a film like this is that you sometimes get bubbles. And those bubbles could be weak spots where the material could tear. So be careful.
Lee Valley recommends using a light oil as a lubricant to carry away swarf. I used camellia oil, the same stuff I wipe my tools down with.
So how does it work? It does cut crazy, crazy fast. I can honestly say that it is the fastest-cutting system I have ever used, hands-down. When renewing the edge on a chisel or a block plane iron, I had to take only about six good swipes on each grit to remove the scratches from the previous grit. Impressive.
The polish from the diamond film is equally impressive. It gives you a wicked sharp edge with a high polish – and the polish will give you more durability.
The oil was a good recommendation, indeed. It made cleaning the film easy. And it coated the edge with oil when I was done sharpening – a good thing.
So what’s the trade-off? As with all sheet abrasives, it’s probably going to be the expense. I’ve sharpened 10 tools on the film and it’s holding up just fine. But who knows how many edges I’ll get out of this film before I have to buy a replacement sheet for $6.20.
And the bubbles trouble me. I got a bubble in the .1 micron film and tore it a tad. The stuff still works fine with the tear, but it does concern me.
The bottom line is that the stuff is amazing when new, but I do want to see how it will hold up in the long run for the way I sharpen. If it holds up, I think it could be an excellent portable sharpening system. So stay tuned. If you are interested in trying the stuff for yourself, you can get it here at Lee Valley.
— Christopher Schwarz
Want to learn to sharpen? Get Ron Hock’s excellent book “The Perfect Edge.” It’s written in plain English for woodworkers and includes a lot of straight talk on steel and abrasives. It’s an excellent part of a foundation library for anyone who uses hand tools.