Despite very accurate measuring and drilling I've ended-up with slight hole misalignment wile building a wooden structure.

While the holes in question have been drilled a bit oversize, that isn't proving to be sufficient in all cases. Some of the holes are not aligning perfectly on both sides of this large 8 inch wide beam.

Holes shown in dashed lines below:


I am wondering if anyone knows of an easy technique one could use to enlarge these deep holes. I can't remove the beams, they weigh about 300 lbs and it's just too much work. The brackets are about 1/4 inch thick. Which means it would be a ton of work to drill out the holes in the metal. It would also destroy the powdercoating.

I'm hoping for some kind of a special boring tool I might not be familiar with that could be inserted into the hole to then enlarge it once past the metal bracket.

  • Although it might not seem it it is often less work to modify the metal versus the wood in situations like this, faster, simpler and more straightforward. The exposed steel is obviously a concern, but that can be treated by hand with a rust inhibitor and then painted with a quality coating of some kind to minimise the risk of rust. But that said there are various strategies for enlarging or moving a drilled hole in wood that might (might) work for you here, but 1) can the metal plate be moved, and 2) how many holes are off?
    – Graphus
    May 10, 2018 at 12:00
  • It's probably going to end-up being a combination. I can't move anything, too large and heavy. It requires a hoist 20 feet up in the air. Right now I'm thinking a Forstner bit that fits the hole in the metal (13/16) might be able to get me a few inches in from both ends. Probably enough to allow for a bolt to go through. Working up at that height adds a layer of complexity that doesn't exist at the workbench.
    – martin's
    May 10, 2018 at 14:21
  • 1
    I don't know if you can shift the beams one at a time to align the holes with the plate opening temporarily, but if so you could fill the holes using same diameter wooden dowels glued into the offset openings. You can then re-drill the hole in the required location using the plate hole as your template.
    – Ashlar
    May 10, 2018 at 16:55
  • Maybe try a metalworking reamer? You should be able to find one long enough to reach the center of your beam, and they have cutting edges on the outside to enlarge existing holes. Really, though, I don't see why you couldn't use a spade bit or auger bit and just put some sideways force on the drill to straighten out the hole May 10, 2018 at 18:32
  • If there were still wood in the centre of the holes I'd love to suggest using a swing brace and an auger, they remain a great way to drill big holes in structural-sizes timbers.
    – Graphus
    May 10, 2018 at 18:37

1 Answer 1


The holes are slightly misaligned, which I assume means that the holes in the wood overlap the the holes in the steel.

Your comment to drill from both sides is the solution that I would pursue. I would redrill the holes in the wood using the same diameter as you originally used. The idea is that the hole that you redrill will follow the course of least resistance which may create a hole that is not perfectly straight, but which will meet in the middle of the wood.

You may not be able to simply slip the bolts through the holes but may have to drive them through in order to follow the possible curved path.

If you are comfortable using a Forstner bit in a portable drill use that since it will minimize damage to the powder finish on the steel. I'm afraid, though, that you will damage the finish and will either have to live with (it's going to hidden and protected by washers or the head of the bolt) or apply some sort of protective paint to the bare metal that will almost certainly appear.

  • I'll mark yours as the answer. I ended-up using a modified version of this. I bought a 1 ft long 1/2 inch drill bit (holes are 3/4 inch. I was then able to drill from each side and "wobble" the bit to cut out material and expand the hole in the require direction, ending up with an eliptical-ish (being kind) hole at each end. After that it was an easy matter to pound the bolts in using a light hammer. Worked like a charm for every hole. Thanks everyone for the ideas.
    – martin's
    May 11, 2018 at 22:03

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