Hands down ... my favorite things to make in the workshop are jigs. Sure making drums, boxes, and borderline art is fun, but making things for the sole purpose of making other things really gets my gears turning. Not only do I enjoy the design process, but troubleshooting any issues that arise, exercises the ole cranial gray matter.
This time, I'm descending further into the rabbit hole ... to make a jig, which will aid in the fabrication of other jigs. Specifically, a jig for my shop made router table, which will have multiple add-ons/attachments for different operations. This first stage will focus on two functions.
1. Cutting discs, rabbeting edges around discs, and cutting circumferential slots.
2. Cutting straight slots, cutting dadoes, cutting box/finger joints.
I'm striving for repeatability, accuracy, and ease of use.
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Step 1: The Deck
The backbone of the beast , which I'm calling the deck, is the foundation for all future moving pieces.
I wanted the deck to be wide enough to provide stability, but not so large that it's unwieldy and difficult to store. I settled on 3/4" plywood - 12" wide x 33" long.
The first step was to cut a key way or two-tiered slot down the center of this board. The first tier is cut with a 1" straight bit. The height was determined by dividing overall plies, as opposed to a specific measurement like 3/8". There are/were 11 plies, so I cut through 5 of them on this first pass. The fence position was set and a stop block was clamped to the edge of the table at a distance of 12 1/2" from the center of the bit [Fig. 1]. The second tier was cut with a 3/4" straight bit - through the remaining 6 plies.
Note: Don't move the fence or stop block, just change the bit and make the cut [Fig. 2].
For the bottom layer, I wanted something thin, but dense. The available 1/4" plywood in my area is low quality, so my go to material is usually 3/16" hardboard. I cut a piece a tad larger than necessary, spread glue on the bottom face of the plywood (the side with the 1" slot), centered it on the hardboard, added another 3/4 board to help disperse pressure, and applied 104lbs of weight - shout out to Bowflex.
Note: Be mindful with the glue near the center slot. You want to avoid squeeze out, as that will create catching points in your key way.
I left the glue to cure overnight and then flush cut the hardboard to the plywood using a flush trim router bit.
Step 2: The Front Stop and Retaining Peg
Auto-alignment is an important concern every time I make a jig to custom fit one of my machines. Not only does it reduce setup time, but it also improves accuracy. For this jig, I'm using a front stop and a retaining peg.
The stop is a strip of 3/4" plywood - 12" long x 1 11/16".
Note: 1 1/16" matches the final thickness of the back clamp in the next step.
For the peg and holes, I'm using a Festool domino. I started with the hole in the edge of my router table top because I wanted it vertically centered for strength. It's just a matter of setting the fence height, holding the tool firmly against the table edge, and making the plunge cut. Without making any adjustments to the machine, I made the same cut in the center of the 3/4" strip. The domino was then glued into the 3/4" strip.
You could do the same thing with a dowel peg. In that case, I would drill the hole through the 3/4" strip using the drill press. I would then clamp it to the edge of the table (flush with the tabletop) and use it as a guide to drill the matching hole in the table. Last step would be to glue a dowel into the 3/4 strip - a dual purpose plug/peg.
The stop and deck were joined using 6 screws. I used the drill press for the countersunk holes, clamped the two pieces together, dialed in alignment with a speed square, drilled pilot holes so as not to split out the plywood, then drove the screws.
Step 3: The Clamp Slot
The back clamp needs the ability to slide, so that there is enough clearance for the jig to be dropped down onto the table. Instead of eyeballing it, I used the top layer of the soon to be clamping block to mark accurate locations.
The top clamp layer is 1/2" plywood cut to 2" x 12". A center hole was marked and drilled at 5/16" diameter. Two side holes are drilled at 1/2" diameter - 1" in from each end [Fig. 1]. With the jig affixed to the router table using the front stop and retaining peg, this board was butted up to the back table edge, securely clamped, and used as a template to transfer hole locations [Fig. 2]. I drilled just deep enough to mark the center point, using a 5/16" brad tip bit for the center hole and a 1/2" forstner bit for the two side holes.
The actual holes were drilled using the drill press and forstner bits:
3/8" for the center hole so that the bolt wouldn't bind - drilled full depth (all the way through).
3/4" for the side holes, so the pegs wouldn't bind and get stuck - drilled around 1/2" deep.
To elongate the 3/8" hole into a slot, I used a 3/8" straight bit on the router table - same fence settings that were used to cut the key way. I made a poor choice in cut direction, which resulted in one end of my slot being torn up. Instead of remaking the entire deck, I drilled out my mistake with a 1" forstner bit and plugged the hole with a section of 1" dowel [Fig. 4]. Once the glue was dry, I cut and sanded the plug flush ... then recut the 2" long slot - this time with a board clamped to the table to hold the deck tight against the fence [Fig .5].
Tip: I had to remove the fence to test fit the jig and locate the deck holes, but didn't want to lose the established location. My solution was to but a block up against the fence on each end and clamp it to the tabletop [Fig. 7].
Step 4: The Back Clamp
The back clamp is a three piece lamination. The 1/2" + 3/4" (2" wide) upper layers match the thickness of the router table top, while the bottom 1/2" layer (3" wide) hooks under the table top and does the actual clamping.
The layers were joined with wood glue and brad nails, 1/2" dowel pegs inserted into the previously drilled holes, and clamps applied. Once the glue was dry, I trimmed the dowel pegs down to a 3/8" exposed height, using the table saw.
The center 5/16" hole needs to extend through all layers, but I made a conscious effort to stop just as the brad point exited the bottom. I could then flip the block over and use this small hole as a centering guide for a forstner bit. 7/8" is the perfect diameter for 5/16" T-nuts. The hole was drilled deep enough to recess the T-nut - roughly one ply.
A bit of epoxy and a few hits from a hammer locks the T-Nut in place.
Step 5: The Clamp Knob
The clamp knob is made from a 2" length of 2" diameter dowel. The center hole was started with a 3/4" forstner bit - to a depth around 5/8", which accounts for the carriage bolt head. The remaining depth was drilled with a 5/16" bit.
The squared shoulder of the bolt will bite into the 5/16" hole, but I added some epoxy for good measure. I then decided to plug the hole with a section of 3/4" dowel stock. Once the glue was dry, I trimmed off the excess at the bandsaw and sanded it flush using the oscillating belt sander.
Step 6: The Router Bit Hole
I took a minute to admire my assembled jig ... then started drilling holes into it.
The first hole is for the router bit. To locate that hole, I used a small V bit. With the jig clamped to the table, I raised the router lift until I heard the bit make contact with the hardboard. The second and third holes are for the lift and lock controls, which I just located by measuring in from the front and side edges of the table top.
All three holes were drilled using a 3/4" forstner bit at the drill press.
Step 7: The Pivot Pin Sliding Key
For the operation of cutting discs, I want an adjustable pivot point, so that I can cut a variety of diameters. We already cut the key way into the deck ... it's time to make the key stock.
The bottom width of the key way is 1", so I ripped several plywood strips to that dimension - some will be for test cuts. The top width is a centered 3/4". I made the cuts on the router table - sneaking up on the cuts both in terms of fence adjustment and bit height, until I had a good fit [Fig. 2]. I did encounter a bit of binding, but it was easily resolved by removing some material from the bottom of the keys with the drum sander [Fig. 3].
Note: I made extra key stock while I had the settings dialed in. I'd rather have it at the ready and never need it than have to make it again.
I made short and long keys, so I could try them both and decide what works best for me. The short keys are 4" in length, while the long keys are around 16".
A center point is marked on each key - 2" in form the front edge - top and bottom. The bottom mark is used to drill a 7/8" recess for a T-nut. The top mark is used to drill a hole for the 5/16" countersunk bolts. I used a step bit for this hole, which worked magnificently.
At this point, I took the time to round the front end of the keys, so that they would slide all the way to tend of the rounded key way. I traced a socket and shaped the part using a 4" disc sander. The T-nuts were hammered into place and then the bolts were shortened for a perfect fit, using an angle grinder for stock removal and the disc sander to remove burrs, as well as flatten the bottom of the bolt.
The pivot pin location is 1" in from the front edge. A hole is then drilled for your pin material of choice. I made two versions since I'll be making discs for various projects and was indecisive.
Version 1: 1/8" steel rod. I cut the rod with bolt cutters and deburred the edges with the strip sander. It was glued in place with a bit of epoxy.
Version 2: 5/8" dowel. I cut the dowels to length using a small parts crosscut sled on the table saw. It was glued in place with wood glue.
How It Works
As you tighten the bolt, it bottoms out on the hardboard and presses the key upwards - lock in tightly and flush with the top of the deck.
The long keys actually work better since you can clamp them to the front edge of the table while tightening the bolt. The sort keys have a tendency to shift a bit.
Step 8: The Sled
For the operation of cutting slots, I want a small sled, which will slide on the main deck like a rail. The sled base is 1/2" plywood - 12 1/2" x 16". I wanted the "sled feet" to be the same thickness as the deck, so I laminated more 3/4" plywood and 3/16" hardboard. The "feet" are 2" x 12 1/2".
The feet were attached with wood glue and brad nails. I used the table saw fence to align the first one flush with the edge of the base [Fig. 3 & 4]. I used the actual jig when attaching the second, so I could get a perfect fit. My measurements ended up being bang on, but this method just ensured the fit wasn't too loose/tight.
Step 9: Disc Operations
Use the pivot pin key to set your desired radius [Fig. 1] and then lower the bit below the tabletop. Place your rough circle onto the pin, hold the work piece firmly (I used a clamp) as you power on the router, and raise the bit up through the material. The rotational direction of your work piece will be counter-clockwise, which is against the bit's rotation.
Safety Note: Do NOT rotate with the work piece clockwise (with the bit's rotation). It will start spinning like a possessed record player and not end well. For the same reason, do NOT let go/lose control of the work piece.
Note: Unfortunately, this router lift doesn't have a gearbox for adding a horizontal lift wheel extension, so I have to do it manually from underneath. Hopefully, I'll come up with some DIY workaround.
Disclaimer: For cutting discs, I'd recommend cutting close to your finish dimension line with a bandsaw and using the router jig for the finish cut [Fig. 1]. The closer you cut .. the more control and less risk. If you throw a square on here and go cutting, you'll be in for a surprise at the end of the cut. The outer "cutoff" won't be secure and the bit will grab it ... turning it into a single or multiple projectile(s).
Same process as cutting a disc, but only raising the bit partially into the material. I'll be using this to make fitted end caps for stave and segmented drum shells [Fig. 6-8].. This method could be used for cutting concentric grooves if so inclined.
Same process as cutting a disc. I could see this being used for making trunnions or specialized clamping slots on jigs.
Step 10: Slot Operations
Hindsight shows that cutting a slot for a stop block would've been a great idea. For now, I'm just clamping a board of desired width between the sled and clamping knob, which works great - just not streamlined. In time, I might just route a groove for some aluminum T-track and make my own stop.
Safety Note: Experience showed me clamping the work piece against the fence provides more accuracy and safety. The right side acts as a climb cut and wants to pull the material into the bit.
Open Ended Slots
Set the stop block for the desired slot length, raise the bit height above the work piece, power on the router, and advance the sled into the bit until you hit the stop block [Fig. 1]
Note: If you want a repeatable slot position in multiple boards, use a side stop block clamped to the tabletop [Fig. 2].
Captive Ended Slots
Set stop blocks for the start and stop points. Hold the work piece firmly as you power on the router and raise the bit up through the material. Advance the sled into the bit until you hit the stop block.
Equally Spaced Slots
My desired spacing was 2" on center, so I cut a test block with that spacing and used it to determine the location for a spacing peg. It was marked and partially drilled with a 1/2" Forstner bit [Fig 3 & 4]. The 1/2" dowel is a nice friction fit.
Once your first slot is cut, you just move it over to the peg and cut the next slot - perfectly spaced and parallel slots. I'm using this for an adjustable roller jig for cutting drum shells, but the possibilities are endless - open slots for clamp racks, captive slots for hold downs on jigs, captive slots for floor vent covers or old radiators, etc.
If you stand your stock on edge against the fence and add a spacer key, you can easily cut box joints. I'd just add a sacrificial backer board so as not to chew up the fence of the sled.
Step 11: Glamour Shots
In keeping with my shop organizational philosophy ... every tool needs a home, so I made a quick plywood hook. It's just two layers of 1/2" plywood with the outer layering wider, so that the jigs clamp hooks in perfectly. For the sled, I just drilled two 1/2" holes and added two screw/pegs to the OSB wall.
One future attachment will be a sled for cutting dovetail slots, for miter splines, in the corner of boxes, as seen in my Secret Valet Box.
I'm sure several more attachments will come to fruition ... I just haven't thought of them yet.
Dimensions [Thickness x Width x Length]
Deck: 3/4" x 12" x 33" (with a hardboard lamination)
Front Stop: 3/4" x 1 11/16" x 12"
Back Clamp Top Layer: 1/2" x 2" x 12" (with 1/2" dowel pegs)
Back Clamp Middle Layer: 3/4" 2" x 12"
Back Clamp Bottom Layer: 1/2" x 3" x 12"
Knob: 2" Dowel stock x 2" length (with 5/16" carriage bolt and 3/4" dowel plug)
Sled Base: 1/2" x 12 1/2" x 16"
Sled Side Runners: 3/4" x 2" x 12 1/2" (with a hardboard lamination)
Sled Fences: 3/4" x 1 3/4" x 16"
Second Prize in the
Build a Tool Contest