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  1. #1
    Join Date
    20th January 2009
    Location
    British Columbia, Canada
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    797

    How to open a centering ring wider without a router

    I have a stupid situation. I need to open a couple of plywood centering rings by about 2 mm.
    I'd like to do it evenly. I would prefer to do it with a jig or some kind of tool but I don't have a router. I would prefer not to hand sand them.
    The rings are 7.5 inch with 98mm MMT openings. I am putting two rings together and putting an aluminum retainer through the rings.
    That's why I want to open them up.

    Does anyone have an idea? I have a drill press and sanding drum but how to jig?

    Someone here has done this and is more creative than I am. Help.

    Thanks in advance!

    Len Bryan
    CAR-ACF S620 L3, NAR 98782 L2, Tripoli 10220 L2

  2. #2
    Join Date
    21st January 2009
    Location
    Glendale, Arizona
    Posts
    1,804
    Centering rings are cheap, order new ones the right size.
    If you value your time at all you will be ahead.

    M


  3. #3
    Join Date
    20th January 2009
    Location
    British Columbia, Canada
    Posts
    797
    Yeah. That thought occurred to me. There's no rush on completing the rocket. That's for sure.
    Even making them from scratch would likely be faster. There's no way to take off a couple of mm with a fly cutter. That's for sure.

    Thanks. (Still curious about other input though)
    Len Bryan
    CAR-ACF S620 L3, NAR 98782 L2, Tripoli 10220 L2

  4. #4
    Join Date
    13th October 2014
    Location
    SouthEastern, WA
    Posts
    5,707
    I use a drill press with a sanding drum. First I print out a CR template using OpenRocket with the correct inner and outer diameters and paste it onto the CR to be modded, then sand the interior to match the new ID. Test fit as the ID gets close for a perfect fit. Takes less time than waiting on new CRs, and really doesnt take long at all. A oscillating spindle sander will work as well depending on ID size.
    Rich

    NAR# 99154

    L3-4x upscale Estes Cherokee-D- AT M1297W 5/28/2016 http://www.rocketryforum.com/showthr...r-rharshberger

    TriCities Rocketeers NAR section# 736 http://www.tricitiesrocketeers.org/

  5. #5
    Join Date
    1st July 2011
    Location
    Pittsburgh, PA
    Posts
    2,927
    Might be able to use a scroll saw or dremel with sanding drum. Darken the amount you want to remove with a pencil, then cut sand until the dark is gone.
    Kevin Wuchevich
    Tripoli Pittsburgh
    TRA 12238

  6. #6
    Join Date
    18th January 2009
    Location
    Maryland
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    11,663
    Quote Originally Posted by cavecentral View Post
    Might be able to use a scroll saw or dremel with sanding drum. Darken the amount you want to remove with a pencil, then cut sand until the dark is gone.
    I mark and use a dremel. A few mm isn't much.
    Dick Stafford
    The member formerly known as the Pointy-Haired Moderator.
    The Original Rocket Dungeon
    Volunteer compiler of product news for ROCKETS Magazine

  7. #7
    Join Date
    26th January 2010
    Location
    Northern California
    Posts
    13,154
    I use a cordless Dremel with a coarse sanding drum to final size the center hole of all my centering rings. As long as you keep the Dremel moving in a circle and don't stop it so it "digs in" in one spot, they turn out fine. Like Dick said, 2mm isn't much. I've taken much more material out of the center hole than 2mm before. I've never had a crooked centering ring. I don't measure or mark, I just sand until they fit.
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    NAR 91107, Level 2

    I really, really hate bugs.

  8. #8
    Join Date
    15th February 2009
    Location
    North Texas
    Posts
    567
    Quote Originally Posted by rharshberger View Post
    I use a drill press with a sanding drum. First I print out a CR template using OpenRocket with the correct inner and outer diameters and paste it onto the CR to be modded, then sand the interior to match the new ID. Test fit as the ID gets close for a perfect fit. Takes less time than waiting on new CRs, and really doesnt take long at all. A oscillating spindle sander will work as well depending on ID size.
    I’ve done the same thing with very good results. (Although I use Illustrator to create the template.) I use spray cement to tack down the guide.


    Tony
    Last edited by manixFan; 2nd November 2017 at 08:08 AM.
    why do people put so much stuff in their sigs?

  9. #9
    Join Date
    20th January 2009
    Location
    British Columbia, Canada
    Posts
    797
    I'm going to take a shot at it. Good advice here. Thank you all for the ideas. If I bollocks it up, I'll order new ones. These ones are here, now and should be workable.
    Len Bryan
    CAR-ACF S620 L3, NAR 98782 L2, Tripoli 10220 L2

  10. #10
    Join Date
    21st March 2011
    Location
    central America
    Posts
    1,966
    I see you're up in B.C. so you may have to find another source. I had a similar problem, and this crops up from time-to-time. My solution is to use a paper mache cone sold as a "Christmas Tree" at Hobby Lobby. I roll a sheet of coarse sandpaper around the cone. I put the CR over the cone and, while pressing down, spin the CR on the cone. Go slow so as to not over enlarge the hole; flip the CR over to keep the hole equal on both sides. Works for paper, wood, and other centering rings.

  11. #11
    Join Date
    20th January 2009
    Location
    British Columbia, Canada
    Posts
    797
    Very good idea! We have Michael's here. That's what I am looking for, some way to make sure it's even. I was hoping to do it on the weekend but I had little time.
    Len Bryan
    CAR-ACF S620 L3, NAR 98782 L2, Tripoli 10220 L2

  12. #12
    Join Date
    19th April 2016
    Location
    Michigan
    Posts
    13
    Set a block with the correct distance from outside of the ring at 6 o'clock, to the outside of the drum sander at 12 o'clock. Pull the centering ring towards you and the block at 6 o'clock, as you rotate the centering ring. In my mind this will increase the inner ring diameter the exact amount that you set the block to and be uniform around the entire ring.

  13. #13
    Join Date
    21st March 2011
    Location
    central America
    Posts
    1,966
    Quote Originally Posted by Len B View Post
    Very good idea! We have Michael's here. That's what I am looking for, some way to make sure it's even. I was hoping to do it on the weekend but I had little time.
    Make a template from heavy cardstock. Use that to mark undersized ring. Sand out to mark (coarse sandpaper to get close, fine sandpaper to hit line exactly).

  14. #14
    Join Date
    20th January 2009
    Location
    British Columbia, Canada
    Posts
    797
    Quote Originally Posted by SteadyMobbin View Post
    Set a block with the correct distance from outside of the ring at 6 o'clock, to the outside of the drum sander at 12 o'clock. Pull the centering ring towards you and the block at 6 o'clock, as you rotate the centering ring. In my mind this will increase the inner ring diameter the exact amount that you set the block to and be uniform around the entire ring.
    This is the kind of jig idea I originally had in mind. I just couldn't quite visualize it. I'm more of a fixer than an engineer.
    The main thing idea is to have a stop of some kind and no easy way for the thing to tear it out of my hands when turning it.

    Len Bryan
    CAR-ACF S620 L3, NAR 98782 L2, Tripoli 10220 L2

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