Forgive me if this is repetition but I coud not find it in a search and it is a technique that can save a lot of frustration. In some cases when you are asked to slide that centering ring over a smaller tube just getting the ring on can be a pain. If this is a relatively small tube to begin with, it can also risk crushing the lip.

When the rings are manufactured there is always a burr on the inside edge from the cutting process. This effectively reduces the inside diameter of the ring. To return to the spec diameter simply insert an Xacto handle (usually a #2 handle) and roll the ring with the handle. The handle will compress the burr and voila! If it is a really tight fit you can angle the handle and simply run it back and forth across the rolling surface - this creates a slightly wider opening to simplify the installation of the ring.

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I always Just used a hammer.

All kidding aside , I usually sand a tiny bevel on the reciving tube as well . In desperation I have peeled out a layer of a ring

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I use a motor casing for that purpose, or a pen for smaller holes. I actually prefer centering rings to be too tight than too loose. Enlarging the hole or reducing the outside diameter is easy; building it up not so much.


Bill

I deburr the tube and ring both. And still have to sand out the ring sometimes. What I occasionally run into is that the ring will delaminate and fall apart on me. I end up having to glue the ring back together, and then sand it out.

It's not a big deal - it's part of the cost of getting to play

Doug

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Some kits' instructions have you "stretch" a ring like that by forcing the nose cone into it. This, of course, works better (for the nose cone) with plastic ones. I've seen that in Quest and modelrockets.us instructions.

I've been known to do the bevel sanding thing with the corner of an aluminum sanding block.

But I like the idea of using a #2 knife handle or a motor casing to do that as well.

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Bernard Cawley
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Good suggestion. For wrapped centering rings, I have had some so tight that I've had to carefully peel some of the paper wrap away, but it is really easy to get carried away and take off way too much.

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Lee Reep
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The most positive thing about rolling the ring as opposed to sanding is that you lose no material. Since the burr was created in the cutting process with a considerable amount of deforming pressure, once the ring is placed on the tube it will attempt to relax to the previous diameter. This propensity is also aided by the application of a water based adhesive such as PVA.

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Gravity is a harsh mistress
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NAR 91005
"The complexity of living is eminently favored to the simplicity of not."

I usually just remove any burr that might be present on the lip of the tube. I can almost always get rings on after that. It's getting them onto the tube in the first place that is often an effort. I always thought that was because they were cut so precisely (especially laser-cut rings), that that the ring had to be perfectly perpendicular to the tube to fit. Once they are past the end of the tube they often seem to slide easier. But you're most likely quite right about the existence of a slight burr on the inner hole of die-cut rings and rings that have been cut from spiral-wound tubular stock. And enlarging the ring by using compression against the edge of the inner hole is a great idea for the reason that you stated. But I have sanded the inner diameter on occasion, very gingerly to avoid taking too much off.

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