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The objective of this How-To is to simplify the purchase of your first hand router as a luthier building up their base of tools. Whether you've never used a router before, never had to consider buying one or just want to go into your next purchase with a more informed choice, the next ten minutes will assist you to make an informed straight line choice. What is a hand router? A router is a compact universal motor that spins a rotary cutting tool at high speed, typically 5000RPM - 30'000RPM. In a hand router, the motor is fitted into a portable base to guide the cutter around the workpiece. Routers are available with a selection of bases with differing end uses, whilst some are permanently built into a more universal type of base. Routers are commonly classified by their horsepower rating from around 1/2HP (~375W) through to 4HP (~3000W) or more. The most common hand routers useful to a luthier are less than 2HP; larger motors become physically cumbersome to manoeuvre around small workpieces and routing operations are rarely as extensive as larger machines are intended to cope with. For further information on the uses of a router, we'll be publishing a Router 101 in the near future. The Router Motor The vast majority of router motors consist of a universal commutating brushed motor. These are inexpensive, compact, have high starting torque and are capable of high rotational speeds. The downside is that they are generally not built to run for extended periods of time and the brushes can physically wear out. If you're interested in how universal motors work, Wikipedia is a good place to start. In general however, it is not required knowledge for judging router A from router B but it does provide useful insight into the secret life of electric motors! Underneath the hood, routers are pretty simple machines The Collet Similar in purpose to a drill chuck, the collet is a locking mechanism for holding a rotating cutter. Unlike a drill chuck, collets are usually swappable between specific cutter shaft diameters. A router that not designed for alternative size collets can be somewhat limited. What size(s) does the router support (commonly 1/4", 3/8", 1/2", 6mm, 8mm, 12mm) and does it come with them, or are they an add-on purchase? Smaller tools such as palm routers are often only capable of handling smaller shaft diameter cutters (1/4", 6mm). Larger routers on the other hand should have a wider range of tool holding capacities. Compact palm routers are adequate for the majority of guitar work, however larger cutters are commonly available with larger shanks only. 99% of the cutters used around guitars are easily found in the smaller diameters so this is rarely an issue for your first purchase. The collet should always rank highly in the things to tick off a potential router purchase. Often, anything but the most basic aspects of the collet are overlooked despite it being something to get right off the bat. Is the collet awkward to access and does it require specific tools to lock/unlock? A collet tightened by a simple spanner can be less frustrating than one that requires a specifically-designed tool that only comes with the router. Can you buy spares or alternative sizes? Collets can wear through use and abuse; not being able to replace the collet can lead to the entire router becoming next to useless. Collet unscrewed from motor mounting. Red button locks the spindle, for tightening or loosening the collet with a wrench or spanner. Top view of collet showing hexagonal outer sleeve and inner split pressure collar Internal view showing inner bearing surface of the collar and sleeve thread Router Bases The two most common types of base that come with routers are fixed and plunge. A router motor mounted to a fixed base allows the rotary cutting tool to protrude through the baseplate by a specific amount and is locked in use. Altering the cutting depth requires that the tool be powered down (and preferably isolated from the mains) before the cutting depth can be adjusted. A plunge base allows the tool's cut depth to be unlocked, altered and re-locked during working operations; the cutter can also be "plunged" into the work. Depth of cut in plunge bases is usually assisted by an incremental depth stop. Better plunge bases also have fine tuners for more accurate settings. Routers with a unibody design are generally dedicated plunge routers. Fixed bases are far more compact and stable than their plunge counterparts. The handles to guide the machine are lower, providing better control through routing operations. Plunge bases have the ability to withdraw the cutter above the baseplate, making them safer when starting up the motor. A fixed base must either have a starting hole ("cutting air") or be advanced into the workpiece from an edge. Plunge base allows operations needing several passes to be carried out with relative ease of adjustment whilst a fixed base is able to carry out more precise, delicate work with the confidence from control. This large Ridgid router has a separate motor with both a fixed and plunge base. ...as does this smaller palm router by DeWalt. The fixed base is intended for single-handed use. Speed control and soft start At the bare minimum, speed control is a huge bonus. Some harder woods are easy to burn (Maple, Cherry, Oak, etc.) and benefit from lowering the cutter speed instead of trying to move the router around the workpiece faster. This reduces final sanding work and allows the routing operations to leave the workpiece closer to a semi-finished state. Larger diameter router cutters also benefit from lower speeds. Doubling the diameter of a cutter doubles the speed at which the outside edge of the cutter travels. Slow speeds are also a bonus should you need to use your router for cutting plastics for pickguards, templates, etc. Heat is also a huge problem for router bits; getting too hot changes the properties of the cutter material, causing premature dullness. Dull cutters also generate more heat.... More advanced speed controlled routers have the ability to electronically monitor spindle speed and compensate for slowdown when performing tougher tasks by applying more power to the motor. This helps safety and quality of work; ensuring that waste material is consistently removed and that there are no sudden speed changes during operations. The name for this feature varies by manufacturer, each one having their own pet name usually along the lines of "constant velocity" or "constant speed". Larger motors often feature "soft start". The nature of the universal commutated motors in routers is their ability to spin up to very high speeds in a fraction of a second. The downside is Newton's third law, "For every action, there is an equal and opposite reaction". A spinning motor suddenly accelerating will cause the body of the router to twist or jump in the opposite direction from the torque. Soft start electronically ramps up the motor speed over a longer period of time, vastly reducing kickback on first powering the motor up. Power Switch Location A consequence of motors having separate interchangeable bases is the location of the on/off switch. Typically, unibody routers have a trigger-type power switch mounted on a handle. Since the handles are separate to the motor itself on swappable bases, most have the power switch located elsewhere on the body itself. Some manufacturers such as Bosch and Porter Cable have worked around this. Generally smaller routers are switched only on the body; whilst not a dealbreaker it is consideration for safe use. Power button location on this Ryobi router's motor Porter Cable's simple workaround on this D-grip fixed router base Modification Potential The beauty of a router is that they can (and should!) be repurposed in all manner of inventive and powerful ways. One example of this is a floating binding jig; commonly ideas like these involve fabricating customised motor holding jigs. Examine the base(s) that come with your router. They usually comprise a metal body with a plastic/composite base which rides on the workpiece itself. Is the base removable by screws, etc. or is it permanently affixed? If so, this enables the router to be used in hundreds of additional applications without large amounts of modification work. The simplest of these is an "offset base". Instead of a round base, a teardrop-shaped plate replaces the existing one with a handle fitted to the narrow end to allow greater stability during edge shaping. Hand router re-purposed for use in a floating binding jig (image courtesy P. Naglitsch) A router that comes with bases enabling flexible modification are instantly a better choice over those that do not. A skilled luthier creates dozens of custom jigs for using their routers in new ways. Unibody routers are less flexible in this regard than routers whose motor is a separable unit. Materials and build quality Contrary to what one might think, plastic is not an automatic signifier of "cheap". Unfortunately, there is little indication of when cheap plastics are being used or high-temp performance plastics. Metal bodies are a good sign of solid build, however the incorporation of performance plastic significantly alters final weight. When used in combination, metal and plastics improve weight distribution and stability. Weight distribution affects how the tool feels in use. Edge-shaping around the horns on a body becomes dangerous with tall routers with a high centre of gravity. The same operation using a router with a lower centre of gravity (fixed base, for example) is an order of magnitude safer and more confident. In short; take the router out of the box at the store, lock the plunge to depth and balance it on an edge. Does it feel tippy and handle like clown shoes on Usain Bolt? With the router still locked, twist it around in both hands. Abuse it! Is there play in the plunge mechanism? Do the handles feel grippy? Are the adjusters cheap plastic that might break off after minor use? Find reasons why you wouldn't buy it and use those reasons to compare against other models on hand. Drives past/around/over corners like '71 Pinto IN BRIEF Your first router should to be nimble enough to handle smaller detail jobs common to all guitar projects. Bigger routers have their place however are usually too cumbersome for bread and butter work. Some tasks - such as copy shaping the outline of a solidbody - are performed better using these larger routers, but smaller motors can carry these out adequately given a patient planned approach. The ideal first router would be something around the 3/4HP - 1-1/2HP range. These tend to be small enough to rout a headstock outline, shape the outline of a body, sink pickup routs and cut electronics cavities; the big work around an instrument. Compact palm routers are affordable, and when bought as a kit have more than enough flexibility to produce accurate and clean results for less than a couple hundred bucks/euros. OUR RECOMMENDED BUYS As of writing, kits such as the Bosch Colt PR20EVSPK, DeWalt DWP611PK or Porter Cable 450PK offer fixed and plunge bases. All have soft start, constant speed control and are the workhorses of many small luthier's workshops; many luthiers end up with several small routers such as these, often dedicated to specific tasks such as in binding jigs or inlay routing pantographs. For a first purchase, routers in this class can manage virtually all jobs you would want them to and continue being useful even when you buy your second (or sixth) router. DeWalt DWP611 kit - no nonsense and easy to work with Bosch Colt/PR20 kit - cheap and eminently reliable Makita RT0700 kit - upmarket from a stable of thoroughbreds
Adhering to some form of best practice is not a necessary pre-requisite of a useful CAD plan. In a non-professional capacity a CAD plan only has to be fit for the purpose it is intended for, rather than following an established set of standards and work templates. That said, giving a passing nod to best practice helps improve the quality and reliability of your plans, personal working methods and raising your game. Google search results for "guitar CAD plan", "guitar dxf download", etc. reveal a hugely varying level of detailing and usefulness. Some "plans" exist as nothing more than a body outline whilst some illustrate every last part of every single component. The answer to "which of these is better?" is not always the expected answer; neither. You've probably already switched off by this point, wondering why you can't just draw what you need to draw and "git r done". That is exactly the point! Your CAD plan only needs to be useful for its intended purpose. The "basic body outline" example is usually because that is all the designer personally needed at the time. Overly-detailed plans ensure that every single bit of useful information for every type of end user is within that one drawing. Either that or it makes a great poster for your shop wall! Do we need some form of best practice? No, but your CAD work will always benefit from a consistent and methodical approach, whichever of the two extremes you fall into. A good plan generally demonstrates: use of guidelines and reference geometry grouping of parts by layer and/or colour straightforward representation without unnecessary detail or ambiguity fitness for the intended end use annotation, readability and easy derivation of measurements These might seem like too much to bear in mind, however they all have a direct bearing on how well your technical drawing work translates to organising work in the shop and the final finished item. Best practice makes your CAD plans productive and useful. Guideslines/Reference Geometry Guitars have a very common underlying structure around which the rest of the instrument is built. For example, a centreline is fundamental to 99,99% of instruments work from. Reference geometry is the structure around which the rest of the instrument is defined. Without it, measurements become unreliable or impossible to acquire. Grouping Individual primitives (lines, arcs, etc.) representing a composite shape (such as a pickup rout) should be separable or at least identifiable from others. Simple colour differentiation, discrete grouping or separation by layers organise your geometry. Without grouping, complex drawings become impossible to interpret usefully. Straightforward representation How much information do you need in your plan? Do you need to draw all of the knurls around the nut of your toggle switch, or would it better be represented as a 1/2" circle and a centre point? Superfluous detail clouds communication of useful information. Structure, relevant grouping and useful visual communication produce easily-navigable and understandable plans. Fitness for purpose What is the drawing for? Does it convey required information as comprehensively and accurately as required? Does it answer any questions you may ask at build time? Is it over or under detailed? CAD plans produced with best practice in mind are an accurate and defensible mathematical representation of the final instrument. Musical instruments are themselves based on mathematical models. Keeping that relationship from the initial design through to the shop work ensures accurate and controlled work throughout. Through subsequent articles in this series we'll mention certain useful examples of best practice which will have a direct impact on your design work. Work smart!
When one thinks of a guitar or a bass, it is easy to think that the number of angles on headstocks, non-flat shapes, radii and sticky-out bits plus various pieces on top of each other would favour 3D; modelling the instrument as a virtual item or set of items. A tangible real-world object often seems more appropriate as one possessing three dimensions. How is it that 2D is still the most appropriate design methodology for the vast majority of instrument design? In many respects, 3D is genuinely useful and definitely relevant for instrument manufacture. As soon as CNC milling becomes part of the equation (or 3D printing of course!) mere flat 2D is no longer sufficient. Whilst basic shape and contour milling ("2.5D" or "3-axis" as opposed to true 3D) have much in common with 2D, what we are in essence doing is directly modelling a real-world item as opposed to drawing a representation of it. The general objective for the 2D approach is to provide drawings which abstractly communicate the metrics, characteristics and specifics of the final product. Whilst a 3D representation has direct relation to the end product, 2D can be far more arbitrary in how it represents details, attributes and the processes required to reach that same thing. To reinforce this comparison, here are two images. One is a 3D representation of a '62 Stratocaster body from a publicly-available Solidworks model, the other is an excerpt from an original Fender blueprint of the same '62 Stratocaster. It should be abundantly apparent that on its own, a 3D model communicates little whilst a detailed blueprint is a goldmine of abstracted specifications and measurements; a virtual instruction manual. The comparison of extremes is perhaps a little unfair in that Solidworks models can have 2D drawings produced from a modelled item. Generally it is not necessary to go up to the level of 3D modelling only to bring it back down to 2D abstractions. Most hand-built guitar and bass designs can have their measurements, layout and specifications represented adequately in 2D and have that translate more or less directly to the final physical woodworking. Operations such as cutting the outline of a body, routing a pickup hole/control cavity, locating the bridge or even planning a neck take place in two dimensions. Whilst 3D definitely offers many powerful modelling and simulation capabilities, in the context of guitar building it is more of an addition than a replacement to "traditional" 2D.
CAD ("Computer Aided Design") in its most basic form is the electronic equivalent of traditional pen-and-paper technical drawing. CAD stores drawn shapes (such as primitive lines, points, curves) as precise mathematical representations or "vectors". Whilst this might seem an overly-simplistic description for anybody familiar with CAD, this description is as true now as it was in the late fifties when the idea was first germinated. That a technical drawing or "mathematical representation of real world metrics" could be electronically stored, transmitted, reproduced, manipulated, merged, transformed and have calculations carried out on it with absolute mathematical precision was a profound innovation. It soon revolutionised industries such as automotive, aerospace, architecture, civil engineering, cartography, military, travel, even graphic design and desktop publishing plus countless other disciplines. Consequently, this precision lent itself perfectly to engineered instrument designs, CNC manufacture, virtual product simulation/testing and even - as a distant cousin - the PLEK system. The tools for CAD work have become accessible to the point of ubiquity with many free CAD packages broadly compatible with high value industry standard software. Autodesk (makers of AutoCAD) even provide an online version of their software ("AutoCAD 360") offering basic sketching, modification and collaboration tools. It is no longer true to say that CAD requires the same financial, educational or time investments or that it is hindered by clunky user interfaces, is unreliable and buggy, or worst of all opaque, unhelpful with a steep learning curve. Whilst some software might seem to hang onto these negative '80s aspects of CAD, the general landscape is now completely the opposite; CAD is completely accessible and easy to pick up. tl;dr version CAD was a revolutionary design invention, initially for specialised industries but now a freely-available tool. For the purposes of planning and drawing a personal instrument, the most basic geometry tools available in virtually all CAD packages are more than sufficient. Even if you want to go down the completist route, this too is not too far removed from the most basic tools. For example, you might want to draw out every last screwhole, inlay, radius, fret, cutaway and cross-section to reliably communicate a final design to a third party. We won't be going into this level of detail, purely because our hypothetical CAD journey is to demonstrate taking a practical design from the computer through to the wood, only highlighting details where they are genuinely useful for this end purpose. Vectors Without going into the deep (and unnecessary) history of Euclidean geometry or mathematics, vector geometry is simply the representation of positions and shapes on a 2D plane. Not entirely unlike dot-to-dot on a sheet of graph paper. Unlike graph paper however, CAD coordinates/vectors are almost infinitely resolvable; numbers can be stored to staggering levels of precision. It is possible to zoom into a drawing pretty much to the limits of yours software's ability (more often, willingness) to do so without "losing resolution" as you would with a pixel-based drawing. In real terms for woodworkers, this might seem like splitting hairs. We couldn't care less about losing 0,01mm here or 1/2048" there. Those are impossible to reliably achieve in the wood anyway; these individual measurement tolerances are genuinely not that useful in the workshop. That said, the ability at the design stage to maintain precision, prevent compound tolerance errors and to ensure that the drawings and layouts we do transfer to timber are free of significant error margins, tolerances and inaccuracies is paramount. It is perfectly reasonable to take measurements in the order of 0,25mm or 1/64" to the workshop, however being this coarse at the design stage could leave you a few mm or a large fraction of an inch out later on in the game! To create an awfully mixed metaphor, "looking after the pennies at the design stage means that the pounds will look after themselves in the workshop" (groan) Putting this together, CAD software handles all of the vector mathematics for you at huge precisions without you having to worry about having to work with big numbers or nasty maths. It's happy to locate all of your fret slots to more decimal places than you could ever use behind the scenes but leave you with two or three in your working measurements - if that's what you want in the workshop. Model Space/Paper Space As touched on earlier, a basic 2D CAD drawing comprises a representation of a flat XY space and a corresponding measurement system (most commonly Imperial and Metric). This environment is often referred to as the "model space" where all of your individual drawing objects are created, manipulated and navigated around in a virtual space using a real-world scaling. A model space is normally able to be divided into separable layers grouping and arranging parts of the drawing, not entirely unlike having drawings separated amongst overlaid acetate transparencies for an overhead projector. A "paper space" is subtly different in that it contains a subsection (sometimes more than one) of your model space; a "window" or defined view into your drawing. A direct example of this may be a focus on a specific part of your model space such as the headstock. The term "paper view" originates from its major use; a printable section of the model space. A single model space can have many paper spaces, with each paper space showing different sections or selected layers from the model space plus annotations relevant to that sheet such as scaling, tolerances, filename, revision dates, etc. The model space is where fundamental design work is done whereas the paper space is how parts of the model space are brought out into the real world as useful drawings. The following images show an example of a finished drawing's model space with an example paper space showing a subsection of the model space and a specific selection of its layers, ready for printing. Drawing Entities A drawing in the model space is populated with a number of mathematically-positioned and dimensioned primitive shapes such as points, lines, polylines, rectangles, arcs, etc. In additional to individual primitives, there are compound, complex or specific entities. A hexagon for example, is a compound of six lines in a specific geometric arrangement. A closed semicircle is a compound of a arc plus a line; in fact, a circle is usually no more than a complete arc. More specialised entities like Bezier curves and splines, etc. provide a comprehensive set of objects from which any object can be formed. Individual CAD packages provide many different drawing tools to simplify the creation of complex shapes. Underneath this, the same primitives are at work. TurboCAD for example, can draw a rectangle with rounded corners of a specific radius. Definitely useful for drawing a soapbar pickup cavity! Underneath this convenient veneer is a set of four lines and attached 90° arcs. The following photo shows a selection of primitives and (slightly) more complex objects: Hopefully it now seems clearer that creating a complex instrument design requires little more than knowledge of a few basic shapes and tools. Coupled with a bit of basic geometry and maths (which you can make the software carry out...phew) plus an organised approach, CAD becomes an powerful, efficient and still a creative tool for designing your next instrument.