How To Use Router Guide Bushings For Inlays
Curious about how to use a router guide bushing for an inlay? In this post, we’ll cover how to determine the size of guide bushings needed and how to use a router bushing for inlay work.
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Some beautiful furniture and woodworking pieces have these perfectly fitting inlays. But how are these perfect inlays achieved? It’s by using router guide bushings! When we went to teach ourselves how to make a wood inlay, we realized there isn’t a lot of good, comprehensive information out there about using bushings for inlays. As avid DIYers, we want to make sure others aren’t stuck and confused about the process, as a beautiful inlay is definitely achievable by anyone!
So maybe you’re new to using routers or an experienced DIYer who just hasn’t used bushings before to create inlays. Read on to see why guide bushings work great for inlays, how to determine the correct bushing sizes, and the full process of making an inlay.
What Is A Router Guide Bushing?
Firstly, router bushings, also called guide bushings, are removable collets that can be attached to a router’s baseplate with a bit coming through the center. It has a small tube that protrudes below the baseplate which the router bit extends through. The outer surface of this tube acts as a guide that rides the edge of a template keeping a consistent distance/offset. This makes it perfect for using with templates to create inlays. Guide bushings typically come in sets.
Why Router Bushings Vs. A Flush Trim Bit
If you’re familiar with all the different types of router bits, you might be asking yourself why would I want to use a bushing set instead of a flush trim bit with a bearing? Well, the best reason is for inlays.
These guide bushings get installed onto the base plate of a router, and they are designed to ride along a template or other feature to turn a standard cutting bit into a template bit. If you have a template for your inlay, you can use a small bit with a small bushing to cut out the perimeter of the positive piece for your inlay. Then you can use a larger bushing and the same bit to cut out the perimeter of the negative for your inlay. These have to match perfectly with the correct offset to achieve the perfect fit in your final piece.
Not all inlay templates come with the inside and the outside components, which means you wouldn’t be able to utilize a flush trim bit as there would be no template to match it to.
You can grab our Free 3D printer files with a Bowtie Template here!
How To Use A Guide Bushing For An Inlay
To use a router guide bushing to cut an inlay for your DIY project, you have to be able to cut two components to match exactly. You need to cut a “negative” (aka groove/recess) in your finished wood piece, and then cut a “positive” piece from a separate piece of wood to go into that negative inlay piece.
Sounds simple enough, but getting those two components to match exactly can be difficult if you don’t know how. So here’s how you calculate the inlays offsets using guide bushings and how to attach and use those router bushings.
Calculating Template Offset For Inlays
To figure out what size bushings you need to use requires a little bit of math. The distance to the cut line of the positive inlay piece is the Bushing A Radius plus the Bit Radius. The size of Bushing A can be whatever you want depending on how close you want the cut edge to be to the template size. I’d recommend sticking to a relatively small size as you likely only have bushings that go up to a certain larger size. After you do the math, you might have to downsize Bushing A if you end up not having a large enough bushing for the second one.
The distance to the cutline of the negative inlay piece is a second Bushing B Radius minus the Bit Radius. You need the cut line to be at the same position for both pieces, so you can solve for the size of Bushing B by using the two equations to derive a simple formula:
The derived formula for determining the size of Bushing B is Bushing B Diameter equals Bushing A Diameter plus two times the Bit Diameter.
Example of Determining Bushing B Size
So let’s walk through an example to determine what size bushing you need to cut out the negative inlay. If you know you want your Bushing A to be ½” and that you’ll be using a ¼” router bit, then you can figure out the size for Bushing B.
Bushing B’s diameter equals ½” plus 2 times ¼”, which would be 1”. So you’d grab a 1” diameter guide bushing from your set to cut that negative inlay and a ½” bushing for the positive inlay, both using the same template when routing. If you used these two sizes, then you would end up with a positive inlay that is a perfect fit for your negative recess. So simple when you have a little formula to use!
How To Install A Guide Bushing
With the bushing size math complete, you can begin installing your guide bushing into your router. First, double-check your router’s baseplate is centered over the collet. If it’s not, the offset created by the bushing won’t be even as it’s not centered on the router bit cutting.
Tip – You can check center a couple of ways, but the easiest way is probably just inserting a bushing the same inside diameter as the bit size you will be using ( ¼” bushing for ¼” bit). Check it’s centered, adjust the baseplate as needed, and secure the baseplate. Then just switch out the bushing for the size you need.
Now to attach the guide bushing, we’d recommend removing the base first as it’s easier to install the bushing when the router motor and bit are out of the way. Then simply insert the main bushing body, and screw the bushing locking ring on from the other side of the base. The threads can sometimes be a little annoying to align correctly, so make sure there’s no play in the bushing once inserted.
Reinstall the base on the router motor and you’re ready to start cutting.
Cutting A Positive & Negative Inlay
Now that you know how to calculate the bushing sizes and attach a router bushing, here’s the process of cutting both a positive and negative inlay piece.
First, you need to have an inlay template ready to go. Templates can be made out of almost any material. We tend to 3D print our templates to have the exact size we want and prefer them to be at least ¼” thick. You can also cut a template out of your material (like wood or hardboard) using a bandsaw or scrollsaw or simply purchase a template.
We’ll show you the process of cutting each inlay component for a bowtie inlay.
1. Do A Test Cut First
Because using a router guide bushing can be so confusing, always do a test cut first, if possible. This will help ensure you have done your math correctly and you will get everything exactly how you want it. It’s also just good to practice with new tools and components before diving into using them on a project to better understand how it feels, get the look you want, and not be disappointed that you ruined some expensive wood or a project you’ve put hours into.
2. Cut A Positive Inlay
For the positive inlay, you’ll want to select a material that’s the thickness of the recess/groove you’re going to cut in your final project piece. It’s a great way to use up scraps of wood, too! If you need to, you can plane it down to the correct thickness.
Next, start by attaching the template to the separate piece of wood for the inlay. You can do this using double-sided tape, hot glue, clamps, or the painter’s tape super glue method The template placement for this positive inlay can be however you want, lining up the template to show whatever wood grain pattern you desire.
Make sure the wood is secured to your workbench. Then using the smaller bushing (Bushing A from above) and the straight router bit, guide the router along the outer edge of the template. Assuming you’ve cut through the material, a perfectly cut inlay piece (a bowtie shape in our example) should pop right out. Set it aside and begin the next step.
3. Cut A Negative Inlay
With the positive inlay cut, now you can cut your negative inlay or recess into your main piece of the project. Similarly, you start by attaching the template using your preferred method. However, the placement on this should be carefully considered to be exactly centered on where you want the final inlay to be. Remember the template is oversized so the inlay will be smaller than the hole in your template.
Now install the larger bushing size (Bushing B from above) and the same size router bit you used for the positive inlay cut. Then begin routing out all the material inside the template. The goal is to remove all the material inside this area to create a recess that the positive inlay can fit into. Ensure you push the guide bushing all the way to the edge of the template to get the full shape cut out.
Remember to make multiple passes if your inlay needs to be deeper than the width of your router bit. Using a bushing on a plunge router makes this super easy to adjust your depths as you go.
After all the material is removed to the needed depth, pull off the template and you’re ready to assemble this inlay.
4. Glue the Inlay Piece
With both the positive and negative components done, all that’s left is to put it together. Start by slathering the negative recess with wood glue. Then slowly push the positive inlay piece into the recess. It should be a tight fit, so you’ll likely need to coerce it in using a rubber mallet. Wipe off any glue squeeze it out and let it dry.
If you set your depth perfectly, it will be flush with the surface of your piece. This can be tricky without a plunge router’s depth stop, so a good alternative is to set it slightly proud of your piece and then use your sander or plane to make it flush.
Repeat this process for any other inlays you plan to do. That’s it, you’ve accomplished a beautiful inlay like a pro for your project!
Are router bushings universal?
Most routers have a standard base plate hole size (1 3/16”), thus most guide bushings sets are based on this standard sizing so it can sit flush with the bottom of the router base. These universal bushings are also known as Porter-Cable (P-C) bushings.
However, there are some proprietary bushings (Bosch & Festool) that only fit on those router brands. These brands’ routers will also typically accept the P-C universal bushings, too. There are a bunch of adapters and sub-bases out there you can buy to make whatever bushing or router you have compatible with one another.
DIY Project Inspiration
Now that know how to use router guide bushings to create the perfect inlay, it’s time for a project! So check out more of our DIY projects articles for inspiration! Or check out some of our DIY plans both on our Site Shop and Etsy Shop!
- The Ultimate Guide to Router Bits: Exploring Types and Applications
- Hubby How To – Modern DIY Platform Bed Frame
- Hubby How To – DIY Modern Headboard With Floating Nightstands
- Hubby How To: DIY Hanging Daybed Swing Plans
- Hubby How To: DIY Tomato Trellis
Hope this guide on router bushings helps you see it’s easy to achieve a beautiful inlay in your next project! Let us know what questions you have on router bushings and inlays in the comments below!
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Disclaimer: This post includes affiliate links, and I will earn a commission if you purchase through these links. Please note that I’ve linked to these products purely because I recommend them and they are from companies I trust. There is no additional cost to you.
