Aligning Misaligned Holes
Sometimes, despite your best efforts, holes you drill for a project don’t quite align with those in the mating parts. It’s maddening, and sometimes you feel dumb because it’s messed up, but there are ways to fix misaligned holes.
This story and these images are illustrations of my own mess. Yeah, it’s a little embarrassing, but fiddly mistakes happen. Such is life in the shop, and so goes some DIY projects. But, enough lamenting. The fix is actually pretty easy.
The Silly Misaligned Holes
This project is a custom carrier for my truck using the standard 2″ receiver. With the parts fabricated, and the hole drilled for the pin (drawbar), it was just a matter of hooking it up. But, the pin for the drawbar would not go in the hole. Almost. It went in one side, but not all the way through as in the photo. Twisting the pin and the fixture still did not make it to fit. And, you can see in the photo, the misaligned holes are are just slightly off. Bummer.
Well, somehow I always feel a little stupid when something does not fit. I thought I measured carefully, and I thought it would go right together. Yet, on the other hand, I do like a close fit, so even a little off and … well, you can see, they don’t quite align.
We can have another discussion sometime about tolerance with less than super accurate machinery. In the meantime, let’s fix it.
Solving the Problem
So, here are three ways to solve the problem. All will work.
- Re-Drill the new hole slightly oversize with a larger drill bit. That’s pretty easy, but it makes for a looser-ish fit.
- Use a rat-tail file or a grinding tool to enlarge the hole only in the area needed. I could just mark the area with a Sharpie while it’s in the receiver, then pull it out and file some on that side. This method is also pretty easy and straightforward.
- Run the same drill bit through the assembly. That will assure the pin fits by forcing alignment of the misaligned holes. This method is dangerous because it will cut portions of both parts (not just the new part with the new hole). However, if the new material is reasonably thin, it will cut more from the thinner piece. This does not work well for thick parts.
In this case, since there is just a small misalignment, and since the new material is thin compared to the receiver, I chose option 3 — run a chase drill through the hole.
Method 3 works pretty fast, usually. However, the drill needs to be sharp, and the drill motor (for a hole this large) must be quite strong because the drill bit will catch the one edge and it will suddenly yank and stop the drill. Just be aware that this technique is a hack job.
For this job, I chose a stout pneumatic drill with a relatively slow spindle speed and tons of torque. Just gotta be careful with fingers, because if the drill bit jams, it will twist violently and potentially smash fingers. Remember, this method is fast and straightforward, but it’s still a hack.
In the end, it worked out well for this project. With the holes aligned, the pin goes right in and there is not much play in the attachment. Nice. Maybe next time I can do a better job marking and drilling to avoid misaligned holes. : )
For the record, we recommend this technique for aligning holes in parts such as the telescoping legs of our Gantry Crane. If they are not drilled perfect, sometimes the misaligned holes need just a little help getting there. Method 3 is pretty easy and does the job well.