Centering Rings

[PhilC]

I've tried many methods over the last couple of decades. I'm having good success and repeatability with a cheap CNC router I bought online. I use it for all sorts of jobs, for example engraving & making Christmas decorations, but it's very handy for making centering rings.
If you want to waste ten minutes of your life you can watch the video here

The workflow is quite simple in Fusion 360 as it allows me to design the object, set up the parameters of the cutter, define cutting path, then it generates the GCode. After that its a matter of sending the GCode to the router over a USB port using GRBL.

 

[jbr]

I use cnc also

 

[lakeroadster]

Autocorrect bit me again. 4" od. For 4" body tubes with 38mm or 54mm center holes for motor tubes.

How thick is the CR, and what material?

 

[bobbyg23]

How thick is the CR, and what material?

Typically 1/4" plywood

 

[lakeroadster]

Typically 1/4" plywood

Heavy Duty!

 

[BigMacDaddy]

I've tried many methods over the last couple of decades. I'm having good success and repeatability with a cheap CNC router I bought online. I use it for all sorts of jobs, for example engraving & making Christmas decorations, but it's very handy for making centering rings.
If you want to waste ten minutes of your life you can watch the video here

The workflow is quite simple in Fusion 360 as it allows me to design the object, set up the parameters of the cutter, define cutting path, then it generates the GCode. After that its a matter of sending the GCode to the router over a USB port using GRBL.

More people need to look at those cheap CNC routers -- great, small, not too messy, easy to use...

 

[bobbyg23]

Heavy Duty!

Big rockets need heavy duty parts.

 

[jqavins]

I use a nice forsner bit.

I like forstner bits, but I would see it as a challenge to center it, since it's hard to see under and get that little pilot point right in the nail hole. Maybe it'd work by feel.

I was thinking to drill two small holes in the base board where the nail goes, carefully positioned so one lets the band- or scroll-saw make the outer cut, and the other positioned for the inner cut. These serve as pilot/positioning holes for the nail. Make the outer cut. More the disk over to the other hole. Cut in from the edge of the disc to then make the inner cut. The kerf slot through the body of the ring doesn't matter once the ring is glued into place, but one can certainly fill it if one likes.

 

[lakeroadster]

Big rockets need heavy duty parts.

I believe in hell-for-stout construction, but 1/4" seems excessive? Can't be to big since your using a 24mm motor... or is it a cluster of 24 mm's? You've got my curiousity peaked... post up soem photo's of that bird.

I am usually making 4" of with 38mm or 54mm motor tube holes.

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Here's how I did my last set of centering rings... worked pretty good. Used home made plywood from (3) sheets of 1/32" basswood.

 

[DigBaddy]

I like forstner bits, but I would see it as a challenge to center it, since it's hard to see under and get that little pilot point right in the nail hole. Maybe it'd work by feel.

I was thinking to drill two small holes in the base board where the nail goes, carefully positioned so one lets the band- or scroll-saw make the outer cut, and the other positioned for the inner cut. These serve as pilot/positioning holes for the nail. Make the outer cut. More the disk over to the other hole. Cut in from the edge of the disc to then make the inner cut. The kerf slot through the body of the ring doesn't matter once the ring is glued into place, but one can certainly fill it if one likes.

My process is to drill a 1/4" hole in what will be the CR. The piece of wood then goes over a chunk of 1/4" rod in a block of MDF that then gets clamped to the bandsaw platform. Cut the outer circle. Then, hole saw/bit with 1/4" arbor centers where needed and drill out the hole for the MMT. If the right size isn't available, going a bit small then sand with flapper wheel; which is somewhat naturally centering as well.

I've made bulkhead-ish templates with some melamine for various sizes, then it's quick to drop the ply and template onto the 1/4" rod in the MDF, trace, then cut.

 

[bobbyg23]

I believe in hell-for-stout construction, but 1/4" seems excessive? Can't be to big since your using a 24mm motor... or is it a cluster of 24 mm's? You've got my curiousity peaked... post up soem photo's of that bird.



______________________________________________________________________

Here's how I did my last set of centering rings... worked pretty good. Used home made plywood from (3) sheets of 1/32" basswood.

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I'm confused. When I cut my own, they are typically for 4" diameter rockets with 38mm or 54mm motor mounts. 1/4" is pretty much the standard for high power rockets.

 

[rharshberger]

I'm confused. When I cut my own, they are typically for 4" diameter rockets with 38mm or 54mm motor mounts. 1/4" is pretty much the standard for high power rockets.

View attachment 500873

I typically do 1/4" in most HPR airframes if only using two rings or the motor is hard hitting/large diameter, if the airframe is 3" or less (not including LPR) then the CR's can be 1/8" birch ply but I may use 3 where if they were thicker I would only use two, its on a case by case design basis/preference so no personal rules for me to share.

 

[lakeroadster]

I'm confused. When I cut my own, they are typically for 4" diameter rockets with 38mm or 54mm motor mounts. 1/4" is pretty much the standard for high power rockets.

View attachment 500873

Thanks / Sorry. When I read "38mm or 54mm" my LPR mind registered "18mm or 24mm".

 

[bobbyg23]

Thanks / Sorry. When I read "38mm or 54mm" my LPR mind registered "18mm or 24mm".

Aha. That makes sense.