Router guide bushings are an extremely useful method of routing blockouts in wood but creating a frame to guide these bushing is time consuming and often a waste of wood. Adjustable frames have been on the market for a while but the cost has been prohibitive. The most prominent model was $360 and that didn't include clamps. A more recent model has brought the cost down considerably but still comes in at around $145 by the time you add the system specific clamps needed to hold it in place. The cost of these systems has necessitated ingenuity on the part of makers to create decent alternatives at more reasonable costs. My design is an evolution of the DIY Adjustable Router Template created by Toolify. His design, while groundbreaking had some limitations which I was seeking to resolve and generally improve upon. It should be noted that the comments made below about his system were not meant with any disrespect but were merely noted as items that I sought to improve upon.
The basic goalsof the project were as follows:
Create a tool-less system - There is absolutely no reason tools should be required for making minor adjustments to woodworking jigs and this jig is no different. Every version out there I found required either a screwdriver or wrenches to make even the slightest adjustments, some including the $360 version even required specialty screwdrivers and there is no excuse for this.
Create a durable and economical system - While Toolify clearly has me beat on the economy of his system it is really not a durable system. Every time the screws are tightened the nuts are chewing into the nut slot channel and over time this will limit the life span. Also the wood had to be cut thin enough in places that the potential for fracture is ever present. My system is made of commonly available aluminum extrusion which will be more durable and as a number of manufacturers make a similar sized product, there is the potential for price shopping to achieve the best value.
Create a self centering design - This was just a minor issue with Toolify's design but it was necessary put the jig on a flat surface each time the joints were tightened or the surface would not be flush which would affect the routing. (Truly his design could have been resolved however by simply rabbeting the ends of the members to remain within the slot.)
Make it easily expandable without significant cost increases - The commercially available models offer longer lengths that can be swapped into their systems but the cost is prohibitive and pieces had to be removed for the longer pieces to be installed which made the changes somewhat of a hassle. My intent was to achieve a means of lengthening members in place.
Require no specialty clamps - All of the systems reviewed required specialty clamps to fit within slots in the extrusion and these clamps generally added $40 to $50 to the price of the system. My goal was to create a clamping system at minimal expense that could then be anchored to the benchtop with common shop clamps which should already be on hand.
Make the jig multi purpose - Let's face it, this type of jig is a one trick pony but with a few simple accessories it can readily be turned into a router based circle cutter or oval cutter.
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Step 1: The Materials
The main material used for this project was a 1500mm length of 20mm x 60mm V-Slot linear rail from Openbuilds. Why, mainly because I already had it on hand but it is also a good material to work with. Beyond that the project is comprised of a fair amount of assorted hardware and some small bits of plastic from a Dollar Tree Chopping Mat which was used for glides.
Low Profile Screws M5 8mm and 20mm lengths
3/4" aluminum angle
3/4" x 1/8" aluminum bar stock
Step 2: Cutting the Main Parts
The 1500mm length was divided into 4 pieces, 2 @ 500mm and 2 @ 250mm. There is no specific magic to the sizes selected and anyone considering building your own should review your own personal needs prior to acquiring and cutting stock.
As my chop saw doesn't do a very good job at cutting square, the lengths were next aligned and shaved with a router to a clean and square condition. Note: It is extremely important for the ends to be square else the jig won't align and tighten properly.
Next, all burrs were removed from the ends and one end of each piece was drilled with a 3/16" bit to receive the M5x8 alignment screws. Be careful not to wallow out the holes. Note, this is not an application where tapped holes are appropriate as the screws will not be driven all the way in to where they tighten against the threads. The screws will be effectively self tapping in this case and will stay put wherever you stop turning.
Finally, small clip angles were cut from 3/4" x 3/4" x 1/8" angle. The clips were cut at 3/4" apiece and a 13/64" hole was drilled in the center of one leg.
Step 3: Making the Glides
I started by cutting a strip from the cutting board 80mm wide and then sliced it into strips. The first 4 were at 3/4" wide to keep it narrower than the 20mm extrusion so it wouldn't protrude above the surface. The next 4 were approximately 10.5mm wide. These need to be cut to fit the width of the channels in the extrusion so it may take a few tries to get the width to the exact size.
Next the holes were drilled into the strips. This was simplified by cutting a couple lengths of 3/4" x 1/8" flat aluminum bar to use as a template. The lengths were 105mm long with 13/64" holes 10mm from each end. Between the two end holes (which were specifically placed to center the 80mm strips) holes were drilled at 12.5mm, 20mm, 20mm, and 23mm with a remaining 9.5mm to the next end hole. After the wider strips were complete, the narrow strips were centered on the template and drilled in the same manner.
Step 4: Installing and Drilling the Locking Clips
Install a clip at one end of each piece of extrusion. Installation is accomplished by inserting a T-nut in the extrusion channel and running an M5x8 screw into it. The clips should be centered on the extrusion and set flush with the base.
Next install one of the drill guides from the plastic glides using the M5x8 screws. The screws thread easily into the extrusion with a little pressure. Do not over-tighten. Drill the base of the angle as shown. The drill guide can then be removed.
Step 5: Major Assembly
Okay, time for the first design change. :/ It became clear that the narrower width of the glides shouldn't extend all the way to the fixing screw as it would interfere with the T-nut that locks the slides in place. So the narrower glides were cut back to 60mm with the end with the 23mm hole spacing being the one cut off.
Now assembly begins. The plastic glides were attached to the ends of the extrusion as shown above in the second picture. An M5x20mm screw was inserted into a thumb nut and tightened and then passed through the outstanding leg of the clip angle to receive a T-nut.
Once the glides are installed it is time to start fitting the assembly together. The assembly was slid together with the narrow section of glide being inserted into the channel of the receiving piece of V-slot while the wider piece of glide remains between the two pieces of aluminum to keep the members from scraping each other. The M5x8mm screws protruding from the ends of the extrusion merely need to be tightened enough that they fit comfortably in the slot. Initially I tried tightening them down to try and hold the two pieces squarely together but quickly realized this created difficulty when adjusting the jig. If one end got even slightly ahead of the other the motion locked up.
Note it is best to create two L shaped pieces and then merge them together as shown in the 5th photo with the edges and ends set flush and the longer pieces up against each other. This is probably the most difficult part of the assembly process. Once it is all fit up it should look like the last photo.
Step 6: Creating the Extensions
Spliced expandability became realistic when Openbuilds introduced its Makerlink line of connectors a couple months ago. Prior to the introduction of the Quad Tee Nuts shown above there were only double tee nuts on the market which didn't inspire a lot of confidence in a project like this.
This portion of the project requires 2 additional lengths of 20x60 V-Slot with the ends squared and a bundle of Makerlink Quad Tee nuts. The set screws require a 2.5mm hex key/wrench.
Assembly is as simple as it looks in the photos. And once installed, the transverse extrusions slide across the joint as if it wasn't even there. Note care should be taken to align the inside faces of the extrusions prior to tightening the set screws.
Step 7: Creating the Clamps
The clamping system takes a different approach than the typical system. In most systems the clamp slides into a channel in the extrusion and then is hooked down under the work bench and tightened. This creates issues with uneven clamping forces due to the ability to reach only so many bench edges with clamps. The clamping forces also had the potential to cause the aluminum to bow upward at the center which would affect routing. My approach was to use side boards to trap the work piece and then clamp those boards to the table with common shop clamps (if needed). The wood side boards are also easily adjustable and considered expendable. If you need to adjust them to a different angle, pull a screw and drill a new hole at the angle needed. If you're doing dadoes across the full width of a board and don't want edge tear out clamp the side boards tight to the edge and run the router right on in.
The width of the side clamps was relatively arbitrary with just a few limitations. The boards were cut to 4" wide based on the length of the adjustable clamp handles and the desire for the end of the levers to remain within the width of the boards no matter which way it was turned. (In retrospect this was probably unnecessary.) Beyond that the only other set dimension was the width of the attachment blocks which was set by the length of the stud extending from the adjustable clamps. I had a 30mm extension so I needed blocks in the 24-25mm width range to be able to connect to a T-nut inside the channel but not bottom out in the slot.
For the clamping blocks I cut five 4" lengths from a 3/4" thick x 25mm wide strip of poplar. I bundled the blocks together with the sides edges up to simplify marking and drilling and marked a center line and additional lines 20mm both sides of center. Cross marks were then added centered on each block. The holes were 7/32" in diameter.
After separating the blocks from the tape, the blocks were set flat and holes were marked and drilled half the width of the block from each end, in this case 12.5mm from the end. The holes were initially drilled with a cheap boring bit designed for installing screws because it also included a countersink and then the holes were followed up with a straight bit to create a clean hole all the way through that the screw wouldn't catch on.
The blocks were installed on 4" x 12" side boards about 1 1/2" from the end. Again, there is nothing magic about the size of the side boards and the size selected just seemed appropriate to what I might be using it for. Once the blocks had been installed in their initial position, one screw was removed and the block rotated perpendicular to its original position and another screw hole drilled. The block was then rotated back to the original position, the screw reinstalled and then the lower screw was removed and the block rotated upward 90 degrees for a new screw hole to be drilled. This creates the 3 basic attachment points for the blocks which provides multiple options when attaching the clamps to the V-slot.
Step 8: Installing the Clamps
Installing the clamps is as simple as running the bolt of the adjustable clamp handle through the center hole of the block and installing a T-nut on the end and sliding the clamp onto the extrusion and setting it where you need it. Once adjusted properly the clamps move with just a simple flip of the lever to create enough slack for the clamp assembly to move effortlessly. Photos 2 and 3 above show the basic system installed and then fastened to the bench top.
The latter 3 photos show usage when needing to clamp to an edge for routing. Place clamp handles in the two holes 40mm apart, add the T-nuts and then slide them up the face channels of the V-slot. Add an opposing clamp to hold the jig in place.
Step 9: Creating the Circle Cutter Attachments
The circle cutter attachments are a fairly simple addition to the system. The materials are comprised of two blocks of wood, one at 2" x 2" and one at 2 7/8" x 4", a 1/8" x 3/4" x 5 1/2" aluminum bar, two thumb screws with T-nuts, two #8 x 1 1/4" wood screws, and a finishing nail.
Start with the small block and drill a hole at the center for the finishing nail. Hole should be snug but the nail should rotate freely within it.
Third photo shows the larger block is slightly thinner than the extrusion. It is important that both be the same thickness to provide a level surface for the router. I used another piece cut from the cutting boards matching the size of the block and fastened it to the block with double sided tape. This solved the problem nicely.
The fifth photo shows the holes required in the aluminum bar. 7/32" holes were drilled at 5/16" from each end and then countersunk holes for the wood screws were drilled 1 1/4" from each end. Screws were inserted to attach the aluminum bar to the block.
Finally, the hole for the router guide was drilled into the larger block. The hole was centered along the length (i.e. 2" down from the top) and 1" from the exposed face of the aluminum bar. The hole was drilled at 1" diameter to match the 1" router guide bushing.
The final photos show the installation of the circle cutter parts into the overall system. The smaller block is trapped at the center of the system and the router block is located as required. The nail is tacked into the cutting material to provide a center pivot. The extension pieces shown in a previous step can be used if the circle needs to be larger than the basic lengths allow.
Step 10: Creating the Oval Cutting Attachments
The oval cutting attachment uses materials similar to the circle cutter with a few additional pieces for the base. The wood blocks in the first photo should be 4" x 7 1/2", 2" x 3", and 2" x 2 7/8" and the 1/8" x 3/4" aluminum bar should be about 3 1/2" long.
The second photo shows a couple pieces of 3/8" thick Delrin with rabbeted edges to fit into a T-slot. As shown they are 1/2" wide at the top and 3/4" at the base but due to limitations of how much my keyhole bit would undercut I later wound up shaving the sides of the lower portion down to 5/8" wide. At the center of each block is an 11/64" hole to receive the pivot screw.
The center base of the oval cutter was made from a piece of 12" x 12" x 3/4" thick MDF. The base needs T-slots cut diagonally both directions for the Delrin sliders. The 4th and 5th pictures show the jig being used to cut the initial 1/2" wide x 3/8" deep slots in the cutter base. The 6th and 7th photos show the finished T-slot and the Delrin blocks in the slot. Blocks should fit snugly but glide without binding.
The 8th photo shows the pivot blocks. The 13/64" hole in the left one is 2 1/8" from the end and centered on the length. The hole in the block on the right is shown incorrectly, something that was identified during assembly. The hole should be 7/8" from the other end.
The 9th photo shows the bottom side of the center pivot block with a washer on the M5x30 screw and the hole the slider block that the screw is to be tightened into. Screw should be tightened to remove slack but should still allow the block to pivot freely.
The 10th photo is the router attachment block. The 1" diameter hole sized to receive a 1" diameter guide bushing is 2" off the right edge and the line for the edge of the 20mm x 60mm V-slot frame is 4 1/8" off the right edge. This allows sufficient space for the 4" diameter base to turn freely. The connection block is similar to the ones used for the clamp blocks. (It is actually the 5th one from the photos.)
The next two photos show the assembled jig with the oval cutter attachments in place. The center pivot is trapped in the center opening of the jig and the end pivot is tightened in place with the thumb screws. Below these two blocks are the Delrin sliders which are set into intersecting T-slots. As shown by the latter photo, the router opening and the pivot bolts should all be in alignment.
The last two photos show proof of concept. The center base was nailed to the plywood being cut with a couple of small finish nails to prevent movement.
Note: to determine the size of the oval, the narrow width is two times the distance from the router to the center pivot and the length if two times the distance from the router to the end pivot.
Step 11: Final Thoughts
Overall I'm happy with the way it turned out but there are a few items I would change if I were to do it again. The thumb screws turned out to be hard to get fingers on especially with the jig flat against the material. A revised version would have the adjustable lever handles all around instead. I would also eliminate the narrower plastic glide set inside the V-slot to center it. It was just too fiddly and thin nylon washers would likely serve the same purpose with less effort.
The other item I would change would be the oval cutter. The amount of framework around the center pivot noticeably limited the range of adjustability of the system. In future versions, I would build the center pivot similar to the end pivot, setting the pivot hole 2 1/8" out from the rail on both and line up both of them along with the router support block along one side of the two extension pieces connected into a single length of rail.
Total cost of the basic frame portion of the jig including clamps was in the $80-$85 range and the extensions with connectors added roughly another $25 to the project. The cost of the circle and oval cutters was minimal as most of the hardware was left over from the packaged quantities purchased for the main portion of the jig. The prices shown do not include any of the lumber used as it was all basically shop scrap.
Thank you for giving my project a view. I hope it has given you some ideas that you can carry though into projects of your own.