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  This is a lesson on how we use a Dremil to make any size centering rings for the rockets we build in the ARC shop.   Things you will need to do this are the following.

1. A ruler or a caliper( this is more accurate) Hardor Freight.
2. A construction calculator( I bought mine at Home Depot)
3. The material you want to cut ( make sure you use the right bit in the Drimel)
3. Dremil Multi tool With a Circle cutter attachment (you may have to go online to get one)
     We modified ours to cut larger rings, we also use this to produce rings for nosecones ( The big O )
     This was a 16in dia X 3ft nosecone.   We made from 1 inch Blue DuPont foam insulation
4. Eye, and ear protection. The Dremil makes a very loud pitchy noise when cutting.
  To start I measure the inside diameter of the tube that I'm going to use. Then I write down the I.D.(Inside diameter)  information. Them comes the math part.
Division,  divide the ID by two, that will give you your center. then make a mark on a scrap piece of paper , or something laying around.  

ex, 2.6 inch  2.6/2=1.3    Simple , I add 1/16th to the outside for a tight fit.
                                        For you metric peps that = 4.064 mm


  I use a 1/8 inch bit in my drill and make a hole at the center mark, Then I make another mark on the outside mark I made earlier.  This will be the Circle
  With the Dremil attached to the hole cutter, and the correct bit in, place Take the center point of the Dremil  place it in the center hole  you made earlier, now loosen the nut on the adjuster, place the bit in the outer hole. Tighten the adjuster nut.  Now look underneath to make sure the bit is slightly below the material you are using. REMEMBER YOUR  EYES You can always sand too fit,  you can't add material.

  Short cut , I make a template out of cardboard and wright the diameter on it
This way all I have to do is go into my file, grab the right one and adjust to what I need

   Always cut the outer circle first then the inner Motor Mount Tube,(MMT)  Again I have a template for the MM Ts
When cutting try to do it in one continuous motion, also keep the tool straight up. move slowly, this will keep the bit from getting too hot.I have smoked a few bits moving too fast.

Fit the completed piece it should be a little big, I'm sure some of you will get the exact fit the first time.

I like to use 1/8 plywood for the smaller rockets. I also use thick cardboard, I get some from the local school. They work great for centering rings or fins.
I have cut up to 1/2 plywood this way. Any thicker than that I will use my router table.

  Again please be careful with this tools have a mind of their own,  never take a power tool for granted.

Thanks and happy building

Rick "scratch " Mckee
Nar 87253 L3
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