Lapping film: Diamone, Aluminum oxide, Silicon carbide, Silicon Dioxide ????

how long they last will depend on how they are used. often time people use too much pressure with these and they dont last very long if you do.

i use the 3M PSA lapping films from toolsforworkingwood which come in Silicon Carbide for the higher grits and aluminum oxide for the lower grits. very light pressure is all you need and they can last a while. here's a writeup they did with more info...

The 3M corporation manufactures a wide variety of abrasive sheets with different types of backing, bonding, and abrasive for all kinds of specialist uses. Woodworkers have embraced the use of these sheets for the "scary sharp" sharpening system, in which you attach sheets of sandpaper to a flat substrate (usually 1/4" or thicker glass) and sharpen away. The main advantage of the "scary sharp" system is its flexibility. It's also a great way for novice woodworkers to be able to sharpen anything without making a large initial investment in sharpening stones.
We've carefully chosen particular films for maximum efficiency of use. For more information about our selection of films, please click here. Based on the recommendations of engineers at 3M and some of our own testing, we put together a selection of abrasive sheets that, while not the most inexpensive available, are easy to use, cut the fastest, and last the longest. We offer 3M Imperial Microfinishing Film and 3M Imperial Lapping film. Both of these products were designed for industrial applications and are not readily available. These films use a high strength polyester film as a backing material. The abrasives are carefully graded and electrostatically oriented for greater cutting efficiently. Even grading is very important for even cutting. You get fewer scratches, and more particles of abrasive at the same grit mean that more of the sheet cuts at the same time - faster and more evenly. Unlike more common Wet-or-Dry papers, these papers are designed for cutting metal and have the grit anchored in a layer of resin. The resin holds the grit to the paper in a very strong bond. You'll notice how much longer they last than regular grade papers. Where possible, we stock the film Type P, which has the hardest resin bond for the longest lasting paper. The abrasive is actually embedded in the resin, so while the film feels sort of smooth to the touch, as the resin wears away more, sharp, abrasive is exposed to the steel. All our films are 3mils thick (.003") to make the film less prone to tearing.

One of the most important things to bear in mind with "scary sharp" is that the paper must be fastened flat to a surface. Taping the edges down doesn't work - the paper bunches up in front of the cutting edge, making the paper prone to grabbing and ripping, and also potentially rounding the cutting edge - so most users either use pressure sensitive adhesive (PSA) backed abrasive paper or spray a can of pressurized rubber cement on the substrate and then you pop a plain sheet of abrasive. We sell both PSA and non-PSA film; the descriptions of each product below can help you decide which one is right for you. For either type of film we use alcohol and a razor to clean up any glue residue.

The silicon carbide films we offer cut faster than their aluminum oxide equivalents, although on the very finest grits both the 1 micron and the very fine .3 micron aluminum oxide sheets will leave a better edge. In general, a good sequence of sharpening is 15 micron (similar to a 1200 grit waterstone), followed by 5 (similar to a 5000 grit waterstone), followed by either the 1 and/or the .3 Micron Aluminum Oxide (similar to an 6000 or 12000 grit waterstone respectively). We use the 40 micron size (similar to a 400 grit waterstone) for really rough blade shaping and doing the backs of old blades when we first get them. Typically, shaping and forming the wire edge of the blade is done on the courser grits, so by the time you switch to a finer grit, the blade really just needs a few strokes. Therefore, the coarser grit sheets get used up faster than the fine grit sheets.
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i didnt know anyone made Diamond lapping filims, ill have to check those out.
 
Diamond film far and away outlast the others by several times (hence the price that is several times more expensive). AlumOx comes next and SiC is last though not by a huge margin. I don't know anything about silicon dioxide abrasive film...

In my experience using them with a thin silicone oil or mineral oil keeps them going for a long time.

As with wet/dry sandpaper - keep it clean and use light pressure with a mostly trailing pass and they will last a good amount of time - lean on them and or allow them to plug and they stop working very quickly.

They all polish about the same per whatever finish they are rated at, exception is the diamond films work very well on high vanadium steels and the others not so much at higher levels of finish.
 
'Silicon dioxide' (SiO2) is what's otherwise known as 'silica', the stuff from which glass is made. It's basically quartz; not very hard, barely harder than hardened steel. I wouldn't bother with that one for knives, except perhaps for steels with essentially no hard carbides; stuff you might sharpen using Arkansas stones, for example, like 1095, CV, etc. The novaculite natural abrasive in Arkansas stones is based in silica, as are the 'garnet' sandpapers intended for use on wood, but not generally meant for hardened metals.

Aluminum oxide and diamond would likely be my preferences, for overall usefulness. Use the AlOx for less wear-resistant steels, up through something like D2 or ZDP-189 (heavy in chromium carbide), and the diamond for steels containing much harder vanadium carbides, like S30V and beyond.


David
 
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Mark Stefaniw said:
where is the cheapest/best place to buy diamond and AlOx lapping films?
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the cheapest is to make your own lapping films, google the PTS method ;)

try it just to get the hang of it, or to get started. you'll learn how often you need to replace the "film" (paper tape), and whether you want to keep using guided strops at all, in future. i, for my part, really transitioned to freehanding and other new hobbies like daytrading, so it was good not to have started an expensive collection
of commercial lapping films. so many bucks saved, which i prefer to invest and potentially lose in my trades. seriously. i use all money, which i earn, to invest, and not to spend or waste on consumption. my new hobby taught me that.
i have 100$ to spend, then i doht spend it but use it to generate another 100$ like all the Robinhood fomos.
i enjoyed being a spending consumer by burning capital for 10years, but my preference has changed ymmv.

the pts method is free since we have paper tape and solid compound already lying around in the household.
 
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