The first stage is flattening the sole of the plane. As I mentioned earlier it is sensible nowadays to expect planes to have tensions within them that need releasing over a period of time. We usually find that a plane needs to be flattened once every six months for the first year or two of ownership. Each time it is flattened the work required seems to be less and less which suggests that the cast iron is becoming more and more accustomed to staying in one position. Flattening a plane is a boring and disagreeable task but it is necessary if you are to have a plane that works properly. We have one poor chap in the workshop at the moment who has flattened a plane by a well known manufacturer four times inside one week. It has taken him over twenty hours and each time he got it flat he came back the next day to find it twisted again. I rang the quality control manager of the company concerned and explained our problem. He was saddened to hear of my difficulties and immediately offered to replace the plane. He couldn't pay for the postage involved in returning the plane because "it would be difficult to get money out of the system" but he did offer to send the gentleman concerned a set of chisels. Although he sent the plane as promised tht chisels had yet to arrive. I did have a lengthy conversation with this gentleman about the nature of flattness. As far as I am concerned if he can get a plane to a mean average of plus or minus 1.5 thou then he is doing a damn good job. The shavings that I require are a good deal more than that at 0.10 mm. The trouble is that once he has done his job the thing moves making the plane useless. This is borne out by the plane supplied by our nameless manufacturer. It was absolutely perfect when it arrived but after a few days in our warm workshop it was decidedly in need of flattening having cupped by more than 5 thou. To get our planes flat or tolerably flat we use a machine table as a register surface. The large table of the spindle moulder is a particular favourite at the moment. On this a roll of fairly coarse abrasive is attached firmly at one end and taped at the other. I think we use something like 30 grit aluminum oxide abrasive for this job (check this with Neil). Fix the iron and the back iron in the plane but sit it well back from the cutting position. If you leave the iron out entirely it changes the stresses in the body of the plane and can give you a different result. Also make sure that any machine bearings are well protected with a cloth as abrasive dust and bearings don't mix very well. Then all you have to do is stand there and push as if you are planing wood and you do it until the sole of your plane is bright and shiny all over. Once this has been achieved you can go to a less coarse grit, such as 70 grit or 100 grit, but basically the job will have already been done and all you are doing is making the plane prettier. This flattening process will not make the plane cut any better but it will make it have the potential of cutting straighter.

Whilst you are working on the body of the plane have a look at the mouth. This should be square across the plane and should allow a smooth passage for the shaving. On no account should you open up the mouth, just make sure the piece of metal that holds the shaving down immediately in front of the cut is clean and smooth.

Next we are going to adjust and set up the shaving aperture. This is the distance between the cutting iron and the front of the mouth. It is a critical opening for this is the aperture through which the shaving must pass. A large shaving aperture and an easy passage for the shaving. This is alright for mild working woods such as Pine or Oak. If you have a difficult wild timber to control then it is necessary to make the passage of that shaving much more controlled. Generally, planes in my workshop are set with a shaving aperture of around about 1.5 mm. To do this you have to adjust what is called the frog.

The frog is the piece of metal screwed to the body of the plane upon which sits the cutting iron assembly. The frog can be moved fore and aft to close or open the shaving aperture. Whilst you are setting this in position, and the only way to do this is by trial and error, check that the frog is properly seating in the plane body. A little engineers blue will tell you if it is touching down on all four contact points. If not there is a danger that the cutting iron will chatter or vibrate and give you less efficient tool.

The next thing to check is how the cutting iron assembly seats upon the top of the frog. The cutting iron is clamped to the frog. If it is only touching in one or two points then there is, once again, a potential for vibration and lost efficiency at the cutting edge. Check this with a smear of engineers blue and if possible adjust it with a few judicious strokes of the mill file. Don't go for perfection here but aim for a good contact as close to the cutting edge as possible and a few points of contact further back near the clamping mechanism. All of these fettling adjustments will have made the plane potentially a more efficient instrument though a job that really counts is the work you do on the cutting iron assembly.

There are two parts to this. The first is concerned with sharpening the iron and I shall be talking next month about sharpening in much greater detail. The second part concerns the "back iron" and how it fits onto the cutting iron. In bold capital letters I should be saying: "How these two pieces of metal relate to one another is critical to the efficiency of your plane". If you are working mild mannered Pine or Oak, the back iron can be fitted well back from the cutting edge, say 1.5 — 2 mm. In that position it does not play a very important role. If however, you are working wild timber such as Cherrywood or Yew then the back iron should be placed as close to the cutting edge as possible. In this position its function is to modify the passage of the shaving through the cutting aperture. It bends the shaving back upon itself cracking it as it comes through the mouth of the plane and not allowing tears to develop.

In order to make this back iron fit to the cutting iron it is essential that the rear surface of the cutting iron is very flat. Before you begin work on flattening a cutting iron check it from side to side with a straight edge or a ruler. If it is convex, that is touching in the middle but not the outsides, you have a problem. If it is concave, that is touching on the outsides but not in the middle, it is possible to get that flat. We generally flatten plane irons on a metal block with 150 grit carborundum grit lubricated with a little water. This is a laborious and grizzly task but it is important that it is done if the plane is to function correctly. Concave plane irons have given my students and apprentices endless hours of arm ache for it is very difficult to get them flat. Once the back of the cutting iron is generally flat it is a matter of careful filing and fitting of the back iron to set the back iron onto that surface without any gap. Check this very carefully with a feeler gauge. If a feeler gauge can get between the cutting iron and the back iron then so can a shaving. It is also important that the back iron is well polished and the point at which it meets the cutting iron is clear. A burr at this point could prevent the smooth passage of a shaving through the body of the plane. Next month I shall talk about the difference between a tool which is generally sharp and one which is keen.

first published in The Woodworker Magazine by David Savage in the series CRAFT OF CABINETMAKING 12