PERFECT RAZOR EDGE ON HAND PLANES (#3 of 5)

RichardMc · November 24, 2004, 5:47pm

BACK SIDE FIRST:

Contrary to what may be expected, even a good quality plane is not manufactured to be sharp and ready to use out of the box. Planes and edge tools leave the factory with rough ground blades that may appear sharp, but are not ready for decent work. Note the rough factory finish on the blade in my photo. Attention to the back side of a blade is mandatory and is equally important as the front bezel cutting edge side. No matter how polished and perfect you get the bezel side of the blade, it won’t get sharp until the corresponding back side meets the edge in the same polished state. This is called “lapping” the backside.

First notice the condition and texture of the back side of the blade. Now place the plane blade’s back side flat on the first coarse grit paper with angled bezel cutting edge facing up and away from you in front. Only the front 1 ½” or so of the blade behind the cutting edge needs to be lapped (flattened) on the paper. The entire back side does not have to be polished. It’s absolutely necessary to keep the blade dead flat on the paper without the slightest rocking up that will ruin the front cutting edge. Read the previous sentence again! Place one set of fingers over the blade to keep it firmly flat on the paper while holding the blade with the other set of fingers.

WE’RE ON IT:

Standing and facing the glass on the bench, with hands and fingers positioned on the blade, begin the procedure by carefully sliding the blade straight across, side to side, left to right across the length of the first 80 grit paper, being sure to keep moderate (not killer) pressure down on the blade to keep it dead flat to the surface of the paper. Avoid going side to side across one exact spot on the paper so you can allow more of the sandpaper surface to work the blade. Avoid pushing the iron’s cutting edge forward into the abrasive paper which would ruin the edge. No circle or figure 8 motions, just straight across back and forth from side to side. You’ll develop your own style for this after a few minutes (style does count here).

After 10 or 15 seconds, take a look at the surface. Though slightly rough starting out on the coarser grit, the surface should become uniform in texture with no flat spots or tiny pits. A flat spot or place where no scratches show would indicate a hollow area in the steel. You can color the front surface of the blade at this juncture with a colored magic marker, then proceed for a bit. Then look to see if there is any remaining color which would indicate a hollow where the sandpaper did not contact and remove the color. If you have a slight hollow continue on that same initial coarse grit, stopping every so often to look, until it’s gone and the surface has uniform looking scratches. Once the entire surface is uniform go to the next grit. Each time you stop, take a few seconds to brush off the papers to keep the dust steel filings from becoming imbedded in the papers. Also wipe the “fuzz” from the blade on a dry soft rag (ok, your t-shirt).

HOWZIT LOOKIN?

You’ll notice the “scratches” from the next higher grit sandpaper are a little finer than those left by the previous grit. The important thing is to keep the blade flat, proceed in a deliberate side to side stroke, and continue only as long as it takes to get a uniform and even looking set of new finer “scratches” from the paper of each consecutive grit. I can’t give you an exact time or number of strokes because it depends on the condition of the blade and your technique, but you’ll be surprised how quickly this goes. But don’t get in a hurry! You’ll likely spend a couple of minutes or so on the initial coarse grit to get things flat unless the blade is in bad shape and needs more work. It might even be useful to drop to 50 or 60 grit for the initial start if the iron is in fairly bad shape. From then on it takes less than a minute on each grit once you get the hang. Maybe around ten minutes is what you should expect from start to finish (I don’t ever time it) to have the back side of your plane blade looking like a mirror. Remember to keep the blade dead flat. If you rock it up or tip the leading cutting edge on the paper you’ll just add more work. This is meant to go quickly, but be methodical and careful. Flat with moderate pressure on the surface of the iron…repeat….flat, flat.

The goal for each grit is not to concentrate on getting the steel more shiny or smooth, but to get a uniform even set of new finer scratches from each grit. The shiny smooth thing is a by-product. Once you get beyond 220 grit, you’ll begin to see a dull shine and the “scratches” will become less noticeable. Remember again to keep it flat on the paper (I say that often). Now is not the time to “oops” the cutting edge off. If you have a small magnifier glass, it’s handy to have for this process. By the time you’ve finished with the 600 grit you’ll see a polish.

DUDE!!

In only a matter of a few more minutes you will finish on the 2,000 grit paper and it will have an actual mirror or chromium look surface. Check out your smile in the reflection. I’m serious! The back side is done. Congrats! See you next class for the front side.