The tool to which we dedicate this article has its roots in the history of carpentry and, if it were not for the interest of a few passionate woodworkers, it would have been forgotten long ago. This type of plane is used for the initial flattening of boards after cutting and seasoning. It is called a roughing plane but is also known as a scrub plane and is for preparing the wood for actual finishing.
Measurements and technical characteristics
Generally, these planes have a length of around 220–250mm or slightly shorter, and are significantly narrower than a regular plane. The reason for this is because this plane is used for longer sessions, with massive and generally localised removal. The preference for this is an agile tool with a blade that is not too wide. Weight is also important and, although over time the major manufacturers have introduced metal models, many still prefer the wooden versions. However, these are personal preferences and there are numerous variations which see the use of longer and wider planes. But there is one feature that all these planes have in common, namely the shape of the cutting edge. It is always curved, and this characteristic allows these tools to be used in cross-grain cutting in an effective and clean manner.
1–3. The classic roughing plane (here in two versions in wood and metal) differs from a common plane mainly in terms of its overall width. Since it is a roughing tool, it is completely devoid of fine adjustments, both for what concerns the advancement of the blade and for the lateral position. The seating angle of the blade is 45°234 & 5. Generally the radius of the cutting edge is not very accentuated. The edges can be set back from the centre by 1.5-2mm. In the case of narrower blades you can go further to obtain a more aggressive profile, but this greatly limits the width of the pass. Generally, this is a personal choice. As you can see, the blades have no central slot. This is because the plane does not include the use of a chip breaker56. Thickness is another distinctive element of roughing blades. In this photo you can appreciate the difference with a standard blade (a Stanley from the mid-20th century). The extra mass serves to give the necessary rigidity during cross-grain work and deeper cuts, which can even reach 1.5mm7. The blade has a curved profile because it needs to cut without chipping. Here you can see the effects of three different blades: a gouge, a blank and a chisel. The first two cuts have clean edges because the edges of the blades remain outside the wood during the action 8. The sides of the cut made by the chisel are frayed because the straight blade enters the wood even with the edges which, instead of cutting the fibre, lifts it, causing splintering9 & 10. Once you have become familiar with the tool, you can set the plane based on the quantity of material to be removed and also the force necessary to proceed with the work. In all cases, as seen here, the edges of the blade remain well inside the sole1011. The same number of cuts were made on this test board with three cutting depths at increasing depths from left to right. With the first cut, the wood shows little or no splintering; in the second and third deeper cuts, more splintering is seen and it looks shaped rather than flattened 12. It is worth focusing on the effects of the rough cut when planing along the grain, which does not mean with the grain. This rarely occurs when working on long and wide pieces. Instead, you are more likely to encounter areas in which the grain changes direction. The splintering is evident in the centre of this workpiece13 & 14. There are a few reasons why the plane splinters along the grain. Firstly, the considerable cutting depth stresses the wood; secondly because of the absence of a chip breaker and lastly due to the large opening of the mouth, which does not prevent the splinters from extending after they are lifted. This last reason can be reduced by modifying the shape of the sole of the plane to create a shaped opening on the blade1415 & 16. The only modification to be made to an ordinary plane iron to transform it into a rough cut consists in rounding the edge. However, the backer iron must be reassembled so that the blade can be fixed on the frog1617 & 18. This example, whose proportions follow Stanley’s no 40 scrub plane, is made by pairing two 3mm brass sides with a 10mm iron plate sole. It is only 46mm wide but has a considerable weight, which provides a fair amount of inertia when you need to cut more decisively18
Before moving on to the first cuts it is good to make it clear that there is no standard setting for working with the roughing cutter. We are referring to the cutting depth and its variations during the progression of the work. It goes without saying that less material needs to be removed as we get closer to the final surface, but we also need to understand how the wood behaves. In some cases, if the grain is regular and compact, the roughing can be started and finished with an aggressive cut. In coarser grain it is good to pay more attention with the first cuts, because even by removing a little the wood splinters more easily. Once some experience has been acquired, the watchwords are attention and continuous observation.
The half slot
The hybrid plane to which this paragraph is dedicated can be understood in different ways: as a cross between the rough cutter and the first grinding of a plane, or as emergency blade for those who don’t have one, and finally as a way to recycle one of those irons in a cheap plane that you had the misfortune of buying, attracted by the very low price.
Homemade scrub plane
There is the possibility of doing it yourself and creating a tool perfectly calibrated to your needs. The methods are different, from the reshaping of a monolithic body to the mixed wood- metal or laminate wood construction.
Blade processing and sharpening
Since the blade, after all, is the main feature of the plane, we certainly couldn’t avoid briefly discussing the shaping and sharpening of the cutting edges. The two operations are similar, with the only difference being that the first is best carried out with the aid of a grinding wheel and the second on stones by hand. The sharpening angle can vary between 25° and 30°. The former is better reserved for the wider blades, more suitable for flattening or pre-finishing, and the latter for the narrow ones, which are entrusted with more demanding tasks.
“Once some experience has been acquired, the watchwords are attention and continuous observation“
19 & 20. In the case of self-building in wood it is always a good idea to equip the blank with an extra hard wooden sole capable of resisting prolonged rubbing on the surface of rough boards2021 & 22. To determine the curvature of the blade, place tape on the blade to highlight the protrusion of the central part. Then rotate the blade sitting on the grinding wheel rest and try to maintain the symmetry between the two sides2223. The grinding work should be carried out in the cleanest and most consistent way possible, to facilitate subsequent sharpening 24 In this phase you can correct the shape by removing more material where needed. For example, in the centre to reduce the curvature as in this case24. In this phase you can correct the shape by removing more material where needed. For example, in the centre to reduce the curvature as in this case25 & 26. Sharpening occurs by dragging the blade across the sharpening stone in a lateral motion. It’s not very easy because you need to maintain the same pressure and the same angle when moving from one edge to the opposite one. Although it is a roughing tool, the back must also be adequately worked; first with a medium lapping stone, and then carefully eliminating the sharpening burrs with the finest stone 2627 & 28. For those who do not feel like sharpening by hand, there is the possibility of using special guides such as the Veritas MKII, on which a roller can be mounted which allows the finishing of blades with convex edges2829. The Stanley No.40 was first produced in 1896, an era when a lot of land was still being developed and most people had no electricity30 & 31. Although today the market for these planes is an almost symbolic demand compared to the the 19th century, scrub planes still appear, almost unchanged from their forerunners, in the catalogues of the major manufacturers3132. These violin-making planes (the largest measures 45mm in length) are used to create the cases of stringed instruments but can also be used for decorative purposes33 & 34. Tools like this Veritas Pullshave are used by chair makers34
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