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How to find the center of a gun barrel?


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I've long had a problem finding the exact center of cylindrical shapes, such as gun barrels or exhaust tips, when trying to drill them out. I know how to find the center of large-diameter cylinders, but can't seem to come up with a way to do it for small ones (less than 1/4 inch)--which means for pretty much all of my needs, I have to eyeball things. Sometimes I get lucky, but more often I fail and the hole I drill is off-center. I usually try to correct it with the tip of a #11 blade, but keep wondering if there is a better way to do this. Any ideas? I'd especially like to know how to do this in 1/72 scale!

Edited by Lucas C.
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If you are drilling out for a model that you aren't allowed to substitute parts. (for example, the OOB rules) then there is a machinist's "quick fix" to this problem.

Find a drillbit the same OD as your round part. Make a "reversed tape" tube, that is wrap it with the stickum outside, then after you have it wrapped, wrap it the "right way" That gives you a tape tube with no stickum on either side.

Put the tube back over your gun, insert the drillbit into the tube and give it a twist or two.

This should leave a depression in your plastic,,,,,you can use that the same way as a center punch is used, for your two smaller drillbits. One drill bit is your tiny pilot, and the second is your finished hole size.

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I NEED to use this! :thumbsup:

I'm actually a big fan of jigs, but I hadn't thought about this one. Hm, I can use a similar technique to drill holes for mounting studs in weapons pylons--just like a doweling jig...

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Can't take credit for that one, Bob,,,,,,an Old Guy taught me that trick in a machine shop wayyyyyy back when I was a Young Guy. Haha

[/quoteea

Any ideas on how to drill a hole in the exact center of a curved surface..such as the leading edge of a rudder... to pin it to the rest of the vertical stabilizer?

Thanks,

Bob

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Unless someone's got a jig for that, I still do it by the "hold your tongue on the side of your mouth justtttt right" method.

The only thing I know of that makes it easier is to always use a tiny drillbit to start with, and move to the correct size after I am sure I like the placement of the hole. I do that for every model drilling job. If you get a "drat!!" moment, that tiny hole is a lot easier to fill than a larger one.

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As of this thread, I would build a jig like a self-centering doweling jig.

Previously, I set up a jig that allowed me to score the center of the part to be drilled with a knife blade. This amounted to stacking sheets of plastic next to the part that I could run the blade along. I then used the score line to locate a pilot drill followed by the target drill. I've never had to use an "intermediate pilot" but I could see that it might be needed since you need to make sure the pilot drill's diameter is no smaller than the web of the next drill.

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[quote

Previously, I set up a jig that allowed me to score the center of the part to be drilled with a knife blade. This amounted to stacking sheets of plastic next to the part that I could run the blade along. I then used the score line to locate a pilot drill followed by the target drill. I've never had to use an "intermediate pilot" but I could see that it might be needed since you need to make sure the pilot drill's diameter is no smaller than the web of the next drill.

That's another good idea. thanks

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Hey Lucas G, As to your gun barrel quandary, I use Triarius' option first. Hypodermic needles are the way to go if you have the means to get them. For smaller stuff, I have a couple of relatives that have given me a lifetime supply of the tiny needles used by diabetic folks. Contact a local pharmacy (mom & pop variety is the best), and ask about purchasing non-sterile hypodermic tubing in 12" lengths. Tell them what you are using it for, and they will usually comply. I have also (rarely) used the tape trick, but in a different way. I put the reversed tape on the part itself. I go through the process, but only drill the hole until about the depth of a couple of sheets of paper. I then thin some black acrylic paint until it's just a little bit thicker than a wash. I start putting paint into the hole in very fine coats. I let each coat dry until the hole looks, well, like a gun barrel hole. By using acrylic paint, I can clean up the edges. I use acrylic paint because the barrel will be painted with enamel paint. If you use acrylic paint, you might want to use enamel or oil paint for you black hole. I have used this method on rare occasions. I almost always use hypodermic needles, because I have a good supple of different sizes. If I use the tape and drill method, I rarely use plastic. I almost always used solid metal tubing.

Edited by balls47
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I saw this tip elsewhere: Find a tube that fits snugly over your gun barrel, and one that fits into that tube- follow? The second hole is centered perfectly on your part. BTW, I always drill these holes by hand, turning the drill carefully. This method will also align the bit for you. Hope this helps-

chuk

Edited by chukw
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I saw this tip elsewhere: Find a tube that fits snugly over your gun barrel, and one that fits into that tube- follow? The second hole is centered perfectly on your part. BTW, I always drill these holes by hand, turning the drill carefully. This method will also align the bit for you. Hope this helps-

chuk

Good Point, chukw. The drilling needs to be done by hand. A lot of times when you give someone some info, we don't even think to put in that info, because we take it for granted that they know. Good job, buddy.

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  • 2 years later...

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