Chris Schwarz's Blog

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.

24 thoughts on “Sharpening with Diamond Lapping Film

  1. milesthom

    Seems like a foolish question, but gotta ask it:

    Whether chisel or plane iron – do you:

    a) push the edge forward, away from your body and into the film,
    or
    b) draw the edge back, towards your body with a pulling motion, as if smoothing the film.

    If anyone is still watching this thread it would be great to know.

    Thanks – Miles Thompson

  2. neptunoPW

    Chris

    About the bubbles.

    I would try a trick that truckers use when they have to stick decals to the truck doors. They slightly wet the surface before the sticking, and by doing this not only the bubbles go away, but they are able to slide the media around and reposition the decal.

    Pedro, Sao Paulo, Brazil

  3. bluegrod

    Christopher,

    I don’t know if you are still monitoring this thread but I to use films to sharpen and like you I use glass and if you spritz the sheet and glass with water that has just a tech of dish soap it will allow you to remove the bubbles with a credit card. You do however have to let it dry overnight so plan ahead. Also, I do not use diamond film I use aluminum oxide film I get from precision surfaces international and the alumox film does just a good of job as the diamond at a much much lower cost. Check it out you won’t be disappointed. The alumox film is used by a lot of guys that sharpen straight razors if that gives you any idea how well it works. Let me know how you make out.

  4. muthrie

    “As far as getting it stuck down without bubbles, there is a trick that might help. Spray the glass with a soapy water solution, place the adhesive side of the film on top of the water, and cover that with a piece of waxed paper. Use a plastic squeegee, working from the center, to squeeze all of the water out. You will be able to squeegee out any bubbles. They use the same procedure to put vinyl stripes/graphics on cars.” by Joe – http://mcglynnonmaking.wordpress.com/

  5. Bear

    I’ve tried the film and had the same experience with “bubbles”.

    By the way, Ron Hock’s book is excellent! In my opinion, it should be required reading for mechanical engineering students. For the woodworker trying to understand the advantages of the different types of steel, Chapter 2 in particular, explains the history and nature of steel in a plain easy to understand language that yields that “aa-ha” moment…

  6. Mitch Wilson

    Woodpeckers carries a similar system. It has much longer sheets of 15, 5 and .3 microns, and they have aluminum honing plates that these are applied to. Very easy to use freehand or with the Veritas Mark 2 honing guide. I built a small, portable, work piece from scraps that the 3 honing plates sit in securely, but with enough wiggle room for them to be removable. The strips can be placed using the adhesive backing, or just placed on the flat surface using water so that the paper covering the adhesive adheres to the honing plate, rather well I might add. And Tico Vogt also has come up with a similar sharpening system.

    1. denovich

      I have both, specifically, the 8″ dia-sharp stones, in Extra Coarse, Coarse and Extra Fine. For durability the DMTs win. Can’t accidentally ruin them in one pass… But for sharpening speed and quality of finish, the film wins hands down. I’ve found that the 15micron film hogs off steel much faster than the Coarse (45 micron) DMT. One thing to note: I’m comparing new film vs. used (but not really abused) DMTs. If you consider that the DMTs cost about 10x as much as film, they better have a lot of life left in them.

      I’m a convert to film. As much as I like how well loose diamond works (and how cheap it can be) it’s a mess, and contamination is a BIG not-so-obvious problem to contend with. Have a few 100 micron diamonds escape and find their way onto some other stone or work surface (or gasp, in some bearing) and embed there and you’ve got a tricky problem to solve.

  7. denovich

    I’ve been experimenting with loose diamonds as well as diamond plates. I knew to expect a quick cutting action and I was hoping that the film would avoid dealing with some of the problems associated with those to methods.

    The film is amazing. It cuts remarkably quickly. I think their greatest advantage is in dealing with steels that are difficult to sharpen (HSS and the powdered metal “super steels”) The diamonds can actually cut/sharpen the carbide grains embedded in the steel resulting in a keener edge. Where a less hard abrasive can do little more than expose those grains (the resulting edge then being a function of the size of the carbide grains.) I’ve also had significantly greater success free-hand sharpening with the diamond film than I have with other methods. I think it’s easier to maintain consistent angles and technique since it requires so few swipes.

    The downside is the durability of the film and its related cost. I haven’t worn out the cutting action of the film yet, but I have snagged the edge on two films, irreparably wrinkling those films. I will try to be more careful in the future. This seems to be the only significant downside… and in light of the results, one that I guess I will learn to live with.

    As far as the bubbles: A mist of water will allow you to apply the film and work out the bubbles. (This technique is recommended practice with other abrasive films I have used.) Just be patient enough to allow it to fully dry and achieve maximum adhesion. Once you have an edge lifting up (especially using oil as a cutting fluid) the film is living on borrowed time as I haven’t found a way to glue it down again.

    I did save my ruined film to use for other things… Like polishing a .25″ dia, 6″ long ground tungsten rod that I’m using for a scraper burnisher. Nothing other than diamonds had any noticeable effect. Chucking it in a drill press and giving a spin with the diamond film resulting in a mirror finish and an absolutely dynamite burnisher. (got mine on Amazon. I can’t recommend it highly enough.)

  8. Carl Stammerjohn

    Is the backing material stiff enough to resist compression? A similar method with sandpaper always ends up rounding over the edges a bit. I’m thinking the plastic backing on the diamond film is much stiffer than the paper in the sandpaper. Correct?

    1. denovich

      Yes, it is both very thin and very resistant to compression. I have had the same complaint with paper backed abrasives… this is not an issue with films.

  9. tsangelltsangell

    Applying window film without bubbles is a process unto itself. I think you use soapy water and a squeegee or roller to iron out bubbles. Perhaps Lee Valley can develop this process as a recommendation.

    I’m interested in seeing how these pan out.

  10. meikou

    I bought the set a month or so ago but I haven’t used it yet as I’m a bit concerned with wearing it out too fast.

    I have a couple of planes I picked up and the blades have seen better days. The 5 1/2 blade needs the edge straightened.
    Any thoughts as to whether the film would work for that or alternatives as I don’t have a grinder?

    1. denovich

      You could try using a belt sander if you have one available, see Derrick Cohen’s site for more details: http://www.inthewoodshop.com/WoodworkTechniques/index.html

      The only non-powered grinding method I’ve found than the diamond film is using coarser diamonds (I have some 100 micron loose diamonds that I use to flatten planes and boy do they cut.) You could use coarse sandpaper mounted on a flat hard surface to do the initial rough shaping (so as to avoid undue wear and tear on the film) before switching to the diamond film. But if you are careful, going straight onto the 15 micron film will work very well.

      1. meikou

        I’m well familiar with Derek’s site but I must admit I didn’t recall using a belt sander. I did wonder about using a file to straighten it.

        I need to set the film up and have at it I suppose. It’s not like it cost a fortune.

  11. CessnapilotBarry

    This stuff might be useful as part of an “about town” sharpening kit.

    Attach the material to a granite floor tile and it would be easier to carry and cleaner than stones when away from the shop.

    1. GordonC

      Chris,
      As a thrifty (parsimonious?) yankee, I have been using paper on glass for the last 5 years and have been either purchasing 15u, 5u and .5u paper from Woodcraft or LV. Having seen the results of the new films, I’m ready to try these. To avoid bubbles, roll the strip on with finger pressure behind the strip as it lays down. Seems to work 99% of the time for me. Thanks for the post.
      R/ Gordon

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