Whiteside 9500 Router Inlay Kits User Manual

Whiteside 9500 Router Inlay Kits User Manual

Inlay of contrasting woods has been an integral part of Öne woodworking for centuries.
With the invention of the hand held routers and guide bushings, the inlay routing with templates has become more common. Figure 1 presents a cartoon of a thin inlay on a thick base. A variant of this inlay example is making a plug to Öll a through hole.

Figure 1: Cartoon of inlay example.

Router inlay kits (Whiteside #9500, Rockler #27593, and others) are available to facilitate the inlay process. The Whiteside and Rockler inlay kits consist of a 1/8î router bit, a 5/16îdiameter guide bushing, and a 9/16îdiameter collar that creates a second (larger) guide bushing. The collar is held in place by an O-ring. The Rockler version is shown in Figure 2.
Other kits are also available. For example, Lee Valley (#04j2807) makes a kit with a 1/4″ bit and would be more suitable for through holes and/or thicker inlay stock.

Figure 2: Photo of Rockler inlay kit.

Table 1: Examples of bit/guide bushing combinations that satisfy constraint Eq (2). router inlay kits can be used without understanding why the bit and the two guide bushings work together.

The objective of using a router inlay kit is to create a hole that perfectly matches the inlay material. Creating the templates for producing this hole is a two step process.

1. 1. The inlay material is used as a male template to create a female template.
   2. The female template is used to create the opening (female mold) to receive inlay material and it radius must precisely match the radius of the inlay material.

Table 1 summarizes the bit/guide bushing combinations of some commercially available kits and some solutions using commonly available router bit/guide bushing combinations. In this table, the following nomenclature is used:

B = bit diameter
G = guide bushing diameter

Where the subscripts 1 and 2 refer to Step 1 and Step 2 of the template construction process. It will be demonstarted in the Appendix that only three of the four parameters (G1; B1; G2; B2) can be independently speciÖed and the fourth must satisfy the constraint equation.

All entries in Table 1 satisfy this constraint equation. Both the Whiteside and Lee Valley solutions are in the form of a kit that contains bit, guide bushing, collar for guide bushing, and centering pin. The Imagine Woodworking is also in kit form as the larger guide bushing diameter is 2″, a size that would be di¢ cult to Önd otherwise.
If you want to create your own router inlay kit, it is helpful to have a set of guide bushings. I have the Wood River (Woodcraft #144625) set of eight guide bushings; Lee Valley (#46j9120) and others o§er similar sets. The BFB (me) solution was simply to start with B1 = 3=16î bit, select a guide bushing diameter G1 from my guide bushings set that will give adequate bit clearance, and then calculate the 2nd guide bushing diameter G2 for B1 = B2. Fortunately, this yielded a guide bushing that was in my set of guide bushings.
If the necessary guide bushing is not in your set, then you must go searching for one. If it not be possible to Önd a commercially available guide bushing, it may be necessary to select another guide bushing G1 as the starting point.
Small Öne work would likely be done with a small bit. If a lot of material is to be removed, then a bigger diameter bit would likely be used. The Stumpy Nubs solution in Table 1 starts with a 1=4îáush trim bit, hence B1 = B2 = G1.
While all the sketches have been for circular geometry, the results can be used for any arbitrary curved geometry. All curves have a local radius that varies along the path. The circle is just a special case of a constant radius of curvature. There are two very important practical considerations in template routing:

1. The bit needs to be centered in the guide bushing. It is next to impossible to keep the point of contact between the outside of the guide bushing and the template Öxed. As the handles of the router rotate during its path, a less than perfect Öt will be produced unless the bit is perfectly centered. Some router tables will accept guide bushings but unless the initial setup was performed with bit centering in mind, unsatisfactory results may be obtained. If you drop a brass guide bushing, check to see if it was knocked out of round.
2. Step 1 is the most di¢ cult part of the process. If the guide bushing momentarily loses contact with the template, the resulting female template will be destroyed, and you have to start over.

Appendix

As an engineer/woodworker, I prefer having a deeper understanding of the ìwhy it worksî as opposed to just being happy with the fact that it works. Sometimes my fellow woodworkers get frustrated with me and my attention to this level of detail. As a retired woodworking hobbyist, I am free to follow whatever path that interests me. What follows is my quest for ìwhy it worksîas applied to router inlay and through hole work.
Before delving into the intricacies of why a typical inlay router kit works, one must have an understanding of how guide bushings work. Figure 3 is an artistís conception of a hand held router with a guide bushing.
The Örst step of using the inlay (plug) as a template is shown schematically in the left portion of Figure 4. The plug (male template) radius R is a speciÖed quantity, and the goal is to route a female mold of the identical radius. This Örst step produces a hole of radius R1.

Figure 3: Schematic of hand-held router with a guide bushing. Taken from Wood Magazine with modiÖcations by author.

Figure 4: Step 1 and Step 2 of the template construction process.

and becomes the female template. In terms of an inlay kit (such as Whitesideís, Rocklerís, …), the smaller diameter guide bushing is used in Step

1. Step 2 will use the collar to create a larger diameter guide bushing.
   From geometry in Figure 4, the radius R1 can be computed from

R1 = R + 1 2 (G1 + B1)

Similarly, the radius R2 can be computed from.

R2 = R1 1 2 (G2 B

Adding Eqs (3) and (4) giv

R2 R = 1 2 (G1 + B1) 1 2 (G2

In order for the two pieces to precisely mate, R2 = R: This yields a constraint between the four parameters (G1; B1; G2

B2) 1 2 (G2 B2) = 1 2 (G1

G2 = G1 + B1 + B2 constraint equatio

Some inlay kits have B1 = B2 = B and G2 is created by a collar on guide bushing 1: In this case, the constraint Eq (7) has a simple geometric interpret

1 2 (G2 G1) = W = B when B1 =

B (8) where W is the width of the c

Please email constructive criticism to the author at bblackwell13@comcast.net

guide bushing/router-inlay.tex 5/5 November 2

References

• Imagine Woodworking™ | Woodworking Design Tools, Courses, & Supplies

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