Sunday, May 10, 2015

How to Sharpen a Veneer Tape Trimmer

I don’t use veneer tape very often. When I build frameless cabinets, I usually face the exposed edges with solid edgebanding cut from leftover wood, so my edges will match the drawers and doors. Once in a while, though, it makes sense to take advantage of
the convenience of iron-on veneer tape, so I do. It makes sense for my built-in-desk, because I’m building the drawers and drawer faces from plywood for speed and for the sake of showing it can be done, as part of a larger project I’m involved in. Without solid wood leftovers to use as edgebanding, iron-on tape is the way to go.

For years, I’ve trimmed it flush with a handy-dandy $19.95 tape trimmer I picked up at Highland Woodworking or Jones Metal Molding or some such place. (Sorry, I can't find a link to the exact same trimmer, just a near equivalent.) In theory, you can squeeze the two halves together, flush with both plywood faces, and trim both edges at once. In practice I trim one face at a time, in case the grain in the tape runs strongly one way or another - - usually it doesn’t, but it seems that whenever I try to trim both faces at once, it does, and one of the edges chips like crazy. There’s also plastic tape to match melamine casework, but I’ve never used that. Some depths of depravity are too deep for even me to plumb.

After 15 years of occasional use and constant neglect, this thing no longer cut well. When you pick up a tool and start using it, but it’s not sharp, you can tell. If you’re in a hurry you might try to just push harder, keep working, and hope for the best, but I am now using this trimmer in one of my classes at Highland, and I want my students to have a good experience, so I decided to get the thing sharp.

This is an "after" picture, but I want to show you the guts. The main cutting blades are fixed, held in the trimmer body with a screw. The cutting edge is the inside end of a “U”-shaped cutout in the blade body. There’s also a secondary blade with a straight edge, mounted at a 45-degree angle to provide a bit of beveling or chamfering after the tape is cut flush. On my trimmer, those seem to have been set out of play, but can be adjusted to engage.

Meanwhile, I needed to sharpen those little U-shaped cutouts. First I made sure the backs were flat on my 700 grit waterstone.

When they were flat I worked up through the grits to 4000. At that point, the backs of the blades were nice and shiny.

I remembered a drill press trick I had heard about, and decided to give it a try. I used a bamboo skewer that fit the “U” perfectly. Without a skewer small enough, I would have tried a toothpick. Smaller still? I guess I’d chuck the toothpick or skewer in the drill press and use sandpaper to “turn” it smaller.

I dipped a short length of skewer into a tube of Tormek stropping paste, which I assume is really fine aluminum oxide. 

That’s all I had on hand; my instinct is to use jeweller’s rouge or some other hard polishing compound, but any fine abrasive paste or polish would probably work.

Chuck the skewer into the drill press, bring the blade to the spinning skewer, and there you have it!

Not shown in these photos: I marked the bevel with a Sharpy before using the drill press, to be sure I was hitting all of the bevel right up to the cutting edge.

How did it work? Just great! At the top of this entry, in the first picture, you can see some of the scraps of tape I cut off testing it. I even tried advancing the bevel blades so they do a little chamfering. This cutter is now certainly sharper than it's ever been, and it cuts quite cleanly as a result.

Next up in this project is to have some fun with a sheet of quartered white oak plywood I bought for the drawer fronts. The next couple of blog entries, though, are going to be about Country Workshops.

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