DIY Centering Rings for the Stubborn Fool

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Well-Known Member
Nov 16, 2015
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I realized after I'd made my most recent rocketry purchase that I'd forgotten to order centering rings. After going through various hare-brained solutions, I found a way to make my own. It requires a little patience but is quite doable; you can make as many as you need in around half an hour.

You'll need:
-A drill. Ideally a drill press, but I used a cordless one with no problems.
-A couple of 2x4, at least 3 feet long. (if the ID of the outer tube is bigger than 3", you may need a 2x6 and a bigger hole cutter)
-A circle cutter like this one:
-Some 1/4" high quality plywood for the rings.
-A sander. I used a bench belt sander, but you could do that part by hand (or using a Dremel) if you're patient and have a vise.
-A jigsaw, skilsaw, or some other saw that can cut curves well

Here's what I did:
1. Set circle cutter so that the INSIDE of the circle is about the ID of the larger tube (Ideally, a tiny bit on the big side, you'll see why in a second). Cut down until you've cut a circle about 1/2" deep in a 2x4. See if the larger tube fits snugly over the "plug" in the middle of the circle. If the circle is too big, adjust it smaller and try again. If it's too small, adjust it bigger, cut a new hole and try that (this is why you want to start big and go smaller - you don't have to cut a new hole).
2. When you're satisfied with the fit, put the plywood over the 2x4s and CAREFULLY cut several holes ALMOST all the way through. If you're using a hand-held drill, hold it as close to vertical as you can. When the cutting bit hits the wood, you'll know if you're straight; it should cut a circle immediately. If it starts by cutting a "C", tilt the drill slightly to make it straight). Ideally, you want to just barely break through a little bit. I'd do at least 2 circles more than you need - plywood is relatively cheap.
3. Go back to your 2x4. Adjust your circle cutter so that the OUTSIDE of the circle is about the OD of the smaller tube (here, aim for slightly smaller because you can "drill out" the same hole. Adjust as necessary until you have a snug fit.
4. Take a deep breath, have a drink of water. Tough part is coming up.
5. Carefully, using the hole in the middle of each of the circles as a guide, cut the inner circles out of your rings.
6. Using the trough in the wood that you cut in Step 2 as a guide, cut out the rings.
7. Carefully sand off the excess.

I'm sure there are much easier ways to do this, but it was late and I was frustrated and I didn't want to pay shipping and wait a few days because I'm impatient. The CRs I made were pretty strong and precise.