Center Ring Jig/Cutter

Note: This is a tool that I personally use to help me build rockets. Using power tools can and is dangerous. I cannot be held responsible for misuse or misunderstood instructions in these pages. Please take care and time in doing projects such as these. Serious personal injury can result in the misuse of these products. Please use common sense. All Liability Waived.

Here is how I made my ring cutting jig. I had used the circle cutter and fly cutter with some success but it’s a lot of work. Making this jig has helped me make in my opinion better quality rings and bulkheads than by my fly/circle cutter and its much faster when it's setup.

This jig makes perfect center rings and bulkheads every time. I have even used it to cut cluster motor centering rings. It requires a router with a routing table. Most routing tables have guide channels to help keep item from moving while they are being routed. Using the jig I made uses this channel to keep the jig from moving so once the size is dialed in, using C-clamp to hold it into place, you can knock out as many center rings and bulkheads you need.

I started with some 1/4 plywood that I had lying around. I cut the piece approximately one and a half feet by two feet. You can adjust this size to fit your router table. Next using some 4 ply 3/16ths plywood, I cut a foot long piece to fit the width of the channel. I then test fit the channel guide in the channel and it was a tight fit. You want it to be tight enough that you can not move up and down in the channel but you are able to move it back and forth through the channel. Then finding the center of the table piece, I drilled four holes into the table top piece and the channel piece including countersinking the table top piece so the center rings would not get caught on the screws (Picture 1). Using some wood screws I had laying around, I wicked the holes with CA and while it was still wet, I installed the screws. Some small portion of the screw was sticking out the bottom, so using my grinder (or a file) to ground down the screw to the wood. Then I test fit the table onto the router table and it fit great.

Next using my routing table with a 3/16ths inch bit, (DO NOT USE ANY SIZE BIGGER. If you use a bigger bit, it can catch the wood and rotate it real fast. It could possibly pull you finger into the bit) I routed the edges of both sides of the jig so they would not interfere with cutting the rings, etc. I then decided to use a sanding drum to cut out divots where I was going to place the pins. This would also give more clearance for the router bit. The next step is installing the pins. The pins are cut from some 3/16 steel rod I had from my old Estes launch pad. I cut them a little over a 1/2 an inch. I mostly use 3 inch BT and up so I placed several pins from 1/2 inch up to 4 1/2 inches (Picture 2). Note that I have found that it is better to put the pins 1/4 closer to the edge to compensate for the width of the bit. Once the pins where cut and the placement of the pins was determined, I drilled the holes with the next smaller drill bit than the 3/16 bit. I wicked the holes with CA and pressed the pins into place. This does not have to be perfect pin placement as you can adjust the ring size by moving the table top closer to the bit. In other words you start off by making the ring over size and slowly move the table top into the bit, testing the size each time you cut it. When you are close, make smaller and small adjustments till you get the prefect fit. Note that a C-clamp is holding the table top each time so as you are cutting the jig does not move. Once the size is found you can knock out several rings in just a few minutes.

I use a 1/8 router bit for cutting my rings. It is easier to get it started. I precut the ring/bulkheads so they somewhat close, but they have even been square. Drill a 3/16 hole in the middle of the wood you want to use. You may have to use a smaller drill bit hole to keep the wood tight on the pin. You don't want the wood that you are cutting to move around on the pin. I have several ready to cut so I can do one after the other. Make sure you are wearing safety glasses when using the routing table. With the jig in place and clamped down, start the router. Keeping in mind there is a sharp bit turning at a very high rate of speed, knowing where the bit IS before you start. This is very important. With the bit turning, I slowly put the piece of wood onto the pin. The bit acts like a drill as you apply slight pressure until it is down onto the jig all the way. MAKE SURE YOU KEEP HOLD OF YOUR WOOD. If you let go, it will chatter and could throw pieces of wood in all directions and possibly break router bit. Take your time cutting the circle. Slowly turn into the bit until the circle is cut all the way. This is how bulkheads are made.

If you want to make center rings, cut all the bulkheads and outer part of the center rings first. That way you have all the outside cuts done without having re-setup to cut more bulkheads or center rings (Picture 3). Once you have all the outer cut work done you can work on the inner cut for the center rings. This is a little different. With outer cuts you start big and work small to get that perfect fit (Picture 4). With inner cut for motor mounts you smaller and work bigger. In other words you start with the bit being inside the ring and move the table away from the bit so the hole gets bigger until it fits. The trick is to not cut the inner hole all the way around. I cut my inner holes a little over 3/4 of the way (Picture 5) shown in upper left hand corner. Do not finish the cut until you have test fit it to fit you motor tube (Picture 6). If you cut the inner circle all the way, you lose the ability to keep it centered and a nice round circle. Then using the motor tube, I test fit them as best I can. Once the size is right (just a snug fit), I will finish with the cut. There will be slight bur on the inner ring that you will need to sand down. This comes from the wood separating at the very last moment of cutting. Once you sanded down this bur, test fit to you motor tube. Slight sand may be necessary as you can adjust this with the next cut to a perfect fit. Finish cutting your other center rings and you’re done (Picture 7). I added 6 more pictures of the jig itself to help illustrate what it looks like better.