Flattening planes

Lutherie

Makers reveal their special techniques

BY YANN POULAIN Luthier based in Montpellier, France

Left to right (a) hollowed sole (b&c) twisted sole (d) hollowed-tail sole (e) half-flatt ened sole (f) flat plane

Planes are must-have tools in the violin maker’s arsenal, but I have never encountered one that’s ready to be used as soon as it’s been bought. Violin making is a series of tasks that require fine, precise craftsmanship, and planes, whether new or old, are never flat enough for our purposes. The sole of an old plane becomes ‘twisted’ over the years, meaning that the left corner of the tip and the right corner of the tail will be in contact with the piece (or vice versa). So it is almost impossible to make a perfect joint with such a plane.

New planes, even those made with the finest craftsmanship, are generally ‘hollowed’, i.e. only the tip and tail area of the sole touch the wood. To compensate, more pressure on the blade or more blade has to be used, which leaves no chance for ultra thin shavings

I decided to re-flatten my planes after my last jointing session had driven me crazy. It was nearly impossible for me to cut off wood exactly where I wanted. I then realized I hadn’t flattened my planes for 20 years, since my time at the Newark Violin Making School. It was a fastidious job but a necessary one to make them work properly. Afterwards I found making joints so much quicker and easier — I promise it’s worth the time and effort.

ALL PHOTOS YANN POULAIN

1 For my method of flattening planes I require the following:

• bench vice

• cast-iron engineering marble

• a coarse metal file (cut 00)

• a paint scraper with a carbide triangular blade (I use ‘Bahco’), or a blunt flat file with its end smoothed and sharpened (it might need to be re-sharpened during the process)

• blue marking paste (‘Micrometer’) and a sponge

• two small metal T-squares

• a small clamp

• a G-clamp

• a non-slip mat for a car boot

• WD-40 lubricant

• cleaning tissue or cotton rag

• latex gloves and ear defenders for safety

Planes with retracted cap iron and adjustable mouth

2 On each plane that needs flattening, I lock the blade and cap iron in place for the whole of the process. I set the blade to be pre-tensioned but retracted, so that it does not cut. If the plane has an adjustable mouth opening, I unscrew it and clean out any wood dust.

Sole marking

3 I use the thick blue marking paste to give a thin, even smear, so when two parts are fitted together the area of contact is marked by the transference of the blue colour. Combined with the surface plate, this paste can reveal gaps as small as 0.05mm.

Using a sponge and wearing gloves, I gently apply the blue marking paste evenly on to the entire surface of the marble, making sure not to leave any thicker spots. I wear latex gloves for this part of the process. In order to avoid getting water on the iron, potentially leading to rust, I first squeeze the sponge completely dry and put it in a microwave for a few seconds. The paste can be thinned with lubricant.

Then I put the plane on the marble and move it several times in a figure-of-eight motion. I am careful not to press down at all, as the weight of the plane is enough.

I clamp the plane in the bench vice, sole side up. The blue spots from the paste reveal where the sole has touched it. (Once this process is finished and the plane is completely flat, blue spots will be visible along the whole surface.)

Scraping lengthways

4 I start to remove the excess metal, marked by the blue spots. I wear ear defenders for the scraping. If the sole is nowhere near flat I use the coarse metal file; otherwise I use the paint scraper (or sharpened file). I start lengthways, being careful not to round the edges, and always scrape in the same direction until the blue spots have all disappeared.

Then I clean off the metal dust and repeat step 2, reapplying marking paste to the marble if needed. The marking and scraping stages must be repeated several times, depending on the state of the sole. Only a very small amount of metal will come off each time.

Scraping sideways

5 I clamp the plane back into the vice and continue taking off excess metal, this time scraping sideways so I can keep track of which areas I’ve already worked on.

Scraping crossways

6 When I’m working near the cutting hole I go crossways so as not to round the edges. I move forward slowly, repeatedly scraping and marking, as many times as necessary until the sole is properly flat. When it is covered with blue, I consider it to be flat enough for the job.

From top to bottom: twisted plane; half-flattened plane; flat plane

7 There’s no need to worry about scratching the surface because it will never be as clean as a new plane – but it will be flat, and the scraping marks will act like a corrugated sole.

Side marking

8 I put the plane on to the plate, on its side, and check the squareness. If the surface is too wobbly I clamp a T-square to the sole with a repair clamp, at the tail end. The T-square must be smaller than the width of the sole. I put a little pressure on the square and check the squareness with a second T-square at the tip, to be sure. Then I move the plane several times, still with just a little pressure on the T-square, in order to mark the side surface with blue.

Side-scraping

9 I turn the plane on its other side and I do the flattening, either with the plane clamped on the bench with a G-clamp, or on a non-slip mat (depending on how much metal needs to be removed). The square can be left clamped until the surface is stable enough for marking. When the side is flat and square, I take off the blade and clean the entire plane so it is dry and free of paste. I lubricate it with the spray and clean it again with tissue. Finally I sharpen the blade and do several shavings as a test run. Now it’s time for fun: a ten-minute jointing session!