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how to make perfect round holes

Old 03-16-2015, 08:24 AM
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Default how to make perfect round holes

when building I have need for holes to lighten the model as well as other requirements. for this I use forstner bits. They cut typically without tear out. I use a drill press and place a block of wood under the wood I'm drilling.

for smaller then 3/8"s I use brad point these type of bits will eliminate most tear outs a typical drill bit causes if your using neodymium magnets for hatch covers these type of bit work great they typically have one the size of the magnet you may have.
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Last edited by JMCHASE; 03-16-2015 at 04:20 PM.
Old 03-16-2015, 08:43 AM
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+1 always use a back block to prevent tearout.
Old 03-16-2015, 04:11 PM
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Drill one side till the center spike shows though the back,
the drill the rest from the other side.

Jenny
Old 03-16-2015, 05:42 PM
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An assortment of different size rotary files and sanding cones/discs (not sure of the correct name) works for me. The trick with the rotary files is they MUST be spun backwards in a reversible drill. If you run them in their normal direction they will bite into the wood and tear and crack it. Running backwards it still cuts thru balsa or plywood with ease and won't tear or crack even balsa as the tool exits the backside of the hole. Sanding cones like you might use with your Dremel tool don't care what direction you run them. We are talking small diameter holes here, 1/8" to maybe 3/4". For larger holes, 1" and up, a hole saw assortment works using a backup wood block as previously advised.

Last edited by 52larry52; 03-16-2015 at 06:02 PM.
Old 03-17-2015, 05:01 PM
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"Sanding drums" is the term I couldn't think of last night. I thought of it today as I was working on the cowl of my used T.F. Cessna 182 ARF project. I was neatening up some existing holes in the cowl trying to make them round and look better, and using a sanding drum to do it.
Old 03-25-2015, 05:33 PM
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A step bit or vari bit will drill a nice round hole too.
Old 03-25-2015, 06:22 PM
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What about making perfect round big holes (for lightening solid stock control surfaces like rudders, for example)?
Old 03-25-2015, 06:56 PM
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Solid stock parts like rudders or vert./horz. stabs can be cut with normal hole saws IF the part to be lightened is clamped top and bottom with a piece of harder wood such as pine. The finer the teeth on the saw the better. You can also drill a hole through a set of wing ribs in your drill press with a regular drill bit if you clamp the set (or part of the set at a time) between two pieces of harder wood. 1/8th thick scrap pine works well on the top and a 2x4, 2x6, or 2x8 on the bottom. The idea is to not have the drill or saw "break out" until it is completely through the balsa section of the "wood sandwich". Or you could buy one of those lazer cutting machines.
Old 03-25-2015, 06:59 PM
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Depends on the wood might try a hole saw i would experement
on a few pieces.Balsa tends to feather i prefer bass wood though for control surfaces
I use a drill press on slow it gives me a more accurste cut.

Last edited by JMCHASE; 03-25-2015 at 11:25 PM.
Old 03-25-2015, 07:08 PM
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I forgot to say that on drilling a set of ribs, I always drill a small pilot hole first for the final size drill to follow. Drilling ribs might be needed when building a wing that was intended to be a 3 channel, no ailerons wing, and making it into a 4 channel set up with two servos mounted outboard in the wing. You need a hole for the servo wires to go through.
Old 03-25-2015, 11:31 PM
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Brad point are inexpensive and come in smaller sizes thats what i would use and
place a block of hardwood under the wood your drilling. I also use a bench top drill press
but a. Steady hand and cordless drill should be ok on occasion i have used brass tubing by finding the diameter i want sharpening the edge with a file and then using it like a leather punch

Last edited by JMCHASE; 03-26-2015 at 05:19 AM.
Old 03-27-2015, 05:33 AM
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Thanks for the tip on larger holes, I bought an interchangeable hole saw set at Lowe's. I'm thinking for single pieces (like the aforementioned rudder) or small sets of two or three layers I might be able to use them as hand saws, turning them backwards so the teeth cut more like knives rather than digging as a saw. If that doesn't work Then the sandwich method should, I have used that before, albeit on much harder woods.

For smaller holes (3/8" or under) in balsa I have found the best trick is to MAKE your own hole saws out of thin wall brass or steel tubing. Use a Dremel with a thin grinding wheel to cut small teeth, use a needle file to sharpen them. You can also epoxy a hardwood dowel sanded to size into the unsharpened end if you think your "hole drill" will need reinforcement for chucking in the drill.

Last edited by FlyWheel; 03-27-2015 at 05:35 AM.
Old 03-27-2015, 07:13 AM
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Further to the brad point tip, you can cut beautiful round holes in covering without tearing by spinning the bit counter-clockwise (backwards) by hand.




I imagine this would also work with Forstner bits though I've never tried it.
Old 03-28-2015, 04:04 AM
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Originally Posted by grosbeak
Further to the brad point tip, you can cut beautiful round holes in covering without tearing by spinning the bit counter-clockwise (backwards) by hand.




I imagine this would also work with Forstner bits though I've never tried it.
Probably not, the center blade wouldn't cut when turning backwards and would stop any progress.
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