Duplicating drilled holes

Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
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Dave Taylor
I have a steel tubing; 12" long, 1" dia., t=1/16"
It has 4 holes drilled through it at various places.
I need to duplicate this tubing and holes.
The holes are the difficult part.
How can I transfer the hole location from the original part to the new part so that they can be drilled?
I have used ruler/tape and such to get these holes very close but I need more precision.
Your restrictions are that it has to be done with my ordinary garage hand tools, I don't have laser tools or CNC machines etc etc. Could scrounge up a drill press but *where* to drill is the problem.
 
Clamp the old one to some saw horses, snap a chalk line from end to end to use as a reference line. Wrap a sheet of copy paper around the tube and poke a hole through the paper into the tube's hole. Do the same reference line on the new tube and mark the spot at the same distance from the end using the paper for a template. Probably won't work 'cause it's past my bedtime.
 
Without more info I'd use a template, too. I don't think you need the chalk line, though. If you cut a piece of paper so it is a tiny bit shorter than the length of the tube, and wraps around about with a little overlap, you should be able to align it to one end, tape it, and use two sharp pencil marks across the overlap to show your alignment. You want to have a straight edge on the paper lined up just to the edge of the tube. That should get you aligned to maybe .02" ? Guessing. Then use a pencil to rub the edges of the four holes. Transfer the paper to the new tube, making sure to align the edge and the pencil marks line up, and tape it. Use a tiny drill by eye to center drill the holes. Or cut the paper where the holes are, and mark center with a sharpie, black or silver.

That's all assuming the holes are relatively small, say 3/8 or less. If they're bigger you probably need a separate step to locate the center of the hole on the paper.

It's a PITA to drill accurate holes in tubing without a drill press and a v-block or some sort of jig. Suggest a cheap drill guide at the least if you don't have one.

Oh, and if the holes are all on the same axis, drilled through, you can drill one in the new one, then pin and tape/clamp the tubes together and use the first tube to guide the second. But it's probaly not that simple a pattern.
 
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Let'sgoflying! said:
but I need more precision.
Click to expand...
For precision will need a drill press with preferably a vise. Using a V block is a full step down but doable if the tube is secured. As to layout/transfer of holes several options.

Apply masking tape on replacement tube and layout holes based on measurements from original using calipers or machinist scale;

Make a 1:1 paper template of original tube and transfer to new tube;

Use guide/transfer pins to transfer holes from original to new tube;

Build simple wooden jig using original for hole locations then place new tube in jig to drill. You can also use item the tube is installed on as a jig to locate the holes if applicable.

For all methods index both tubes to confirm proper locations and start with pilot holes at each new hole location.
 
Don't use paper for a template. Wrap it using a single sheet of drafting Mylar, which is much more dimensionally stable and transparent. Mark the Mylar with a very sharp pencil. Center punch through the mylar. You will have to use some means (facing pencil lines?) to make sure the mylar hole transfer system isn't twisted however. With care you should be able to repeat hole locations within about .020 inch, providing the tube diameters are the same.

A neat challenge.....:)
 
Definitely use a drill press. With a hole that small, the drill bit will tend to bend if you do not center the bit at the highest point. I also like to start the hole with a pilot hole bit. I used the ones sold by Harbor Freight but my project did not require precision.
 
If you don't have a drill press, one of those attachments you put on your power drill can be very helpful. I bought one about 20 years ago and it's so good I haven't taken it off. It allows you to drill exactly perpendicular to your work surface. It has notches on the platform, so you can drill exactly in the center of a cylindrical object.
 
I use one of these to get a good mark for the pilot bit before up drilling:

12-01874.jpg

https://www.aircraftspruce.com/catalog/topages/utilityPunch.php
 
The holes are done and it is perfect.
Marking the holes was a laborious time-consuming task that almost defeated me. I spent hours with measuring tools, stencils, various lamps, and such.
On 2 of the 8 holes, my pilot hole was way off (well, they were within the the radius of the final hole) but I am good at fixing my mistakes and corrected them to center!
All with a hand drill (I have a good center punch to start them).
Part of the problem was the original holes were not in alignment along the tube with each other, and the drill press must have been canted at an angle when they did them.
Producing a reference line along the 12" of pipe was also a huge issue. In the end, I found that the eye can pick off misalignments better than anything. The first test reference line looked ok til looked at closely - it was obviously a spiral around the length of the tube (a slight spiral but obviously not aligned with the tube's axis).
Re-measure, check other ways to reference it, redraw it. Check, test, visual confirmation, change the lighting, go out in the sun. 'That's the best we can do'...drill. (I had spare stock tubing but did not need it.)
Thanks for all the encouragement. I like metal work but I don't find any of it easy.
 
I am the definition of a DIY guy, but every now and again I'll part with a couple bucks and have a machine shop do the really high-precision stuff. Hard to compete with laser-measuring tools and such.
 
I would split the old tube, end to end, giving me two half-tubes. One would have the holes in it, 90° to the cuts. Spread that one a bit and fit it over the new tube and secure it there, with hose clamps, maybe, then do your marking or drilling. A milling machine with a 1/4" end mill or slot drill would work nicely. By hand with an electric drill would be harder, but with care you could do it.
 
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