Very simple, but can save a lot of headaches Materials: a flat piece of bar stock, a hole saw arbor, a nut, a long 1/4 inch bit. drill a hole in the bar stock on a squared up drill press. Weld the nut to the bar stock and screw the arbor into the nut. Drill a pilot hole to one side of tubing Then hold or clamp tool to tubing. when you run the drill bit through you will get a corresponding hole on the other side, in perfect alignment. Works good in tight spots. Simple but effective. I also use it to square my drill press I guess you could machine a groove into the bar stock and use it for round tube
Good tech reruns are always welcomed. I've only had to do this one time when it really had to be in alignment. LOOKS EASY.......not!
Another alternative is to go to an industrial supply house and ask for "drill bushings", they are made from hardened steel, come in many drill sizes and lengths.
That won't help get the hole in the wall of the opposite side in alignment, actually I don't see what that accomplishes at all.
If we're talking drilling through both walls of square/rectangular tubing and making the holes dead looking at each other, no I wouldn't even try. That's only slightly thicker than a sheet of (heavy) paper, I dont see how that will keep the drill bit square with the world, not that I trust them but you might as well just use a drill motor with the bubble level in it.
I have an occasion to drill through a 2" frame rail at a slight angle. So I made this, using 3/4" DOM tube with a 1/4" hole.
Why not just use a drill press to drill a straight hole through a thicker piece of steel or a piece of tubing and use that as a guide? Why bother with welding on a nut?
This type of tool was used by tooling when I worked at Boeing. The bottom plate was referred to as a drill block and the switchable bushings were referred to as drill bushings. We also used what was called a "bomb sight". It was a clear plastic cylinder with crosshairs carved into one end. You placed it in the drill block and aligned it to the mark on your material. The block was then secured and the sight removed and the selected drill bushing installed in the block.
I think the point of the CD is to align the reflection of the drill bit with the real bit and call it "square". It's not for all situations, just those "close enough for government work" ones. I like the arbor/bushing idea maybe also as guides for starting thread taps by hand. I'm probably batting way under .500, which is great for baseball but for getting threads straight by hand, not so much.
Parallax is a term that means things appear differently when viewed from different positions. The machinists in the crowd will understand right away, even reading a micrometer can be skewed, right DDDenny? Forget that compact disc deal, you will have better luck with a hole drilled with a drill press through a 2x4. Hold that against the wall and it will keep your drill square enough to get the hole on the other side of the wall right where you need it. Need to drill and tap squarely? Same deal, but use a metal block of decent thickness. One hole for the tap drill and another for the tap. Pretty basic but some guys never bother.
You don't need to be a machinist to understand parallax error but you need to be ignorant to think it occurs on a 360* mirror. All I have provided is a little tip as per the thread title which has nothing to do with drilling through both sides of anything. Some of you full timers need to open your minds or lay off the fiberglass .
I brought this thread back to the top because I thought it had merit. Then it degraded into talking about drilling holes with CDs of all things. Reading the original posters first post it’s obvious that he was in fact talking about drilling precise holes through both sides of tubing. Quoted here: “Drill a pilot hole to one side of tubing Then hold or clamp tool to tubing. when you run the drill bit through you will get a corresponding hole on the other side, in perfect alignment. ” So since that’s what I need to do because I’ve decided to run my brake lines through the frame for the front brakes on my RPU I made my own version of the hole jig. A piece of 1” key stock because it’s nice and square, drilled and tapped for an old hole saw arbor along with a long 1/4” drill bit and I’m good to go to drill precision holes through my frame for the SSBC through the frame brake fittings.
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