Removing broken screws from spoilboard

I did go down some rabbit holes looking for better solutions here. I did find these interesting paper punches and tried one of them. It’s a hardened steel tube punch, hollow all the way up, fairly thin walls. It’s exactly what I was imagining trying. They come in different diameters so it can even be matched to the size of the object needing removal.

It worked quite well for about the first 1/2" of depth. I pulled it out several times and found the tube had MDF packed inside it as hoped, poked it clear with a pin, and pushed in again. But then (mostly expected this) it had no room to push MDF out of the way and stopped. I got a little further tapping it with a hammer, but only a little, then I escalated the force and the tip of the punch broke (it’s hardened steel, so it’s going to break not bend). Comparing the depth it’s going to with the side of the spoilboard, it looks like it’s stopping about where the two sheets of MDF are glued together. The faces of MDF are notably harder than its bulk, so it may just be stopping there because of that, or it could be a coincidence.

Which was itself a new opportunity- the punch only has an inner chamfer edge, so twisting doesn’t really cut. But the rough break made a sort of a tooth. I tried twisting by hand, like it was a very long, very narrow hole saw. It’s just MDF, so I was hoping it would start grinding away under hand pressure. But no luck there. One thing that I thought of later is there’s no flutes to lift up debris, so I may just be rubbing the debris from the first push and it needs a puff of compressed air to clean it out and it might start cutting again. I could use a Dremel cutting wheel to grind more of a tooth shape in the end of the punch.

Any thoughts?

If you can’t dig them out from the top, I have a pneumatic nail punch. It’ll blow the screws through the bottom. You’re welcome to give it a try.

I’m picturing the strategy of punching them through the bottom as just causing major damage though. A nail could potentially be pushed through, but it seems like it would cause more damage. There was only one incident where a few steel nails- which should never be used under any circumstance- ended up in the table, and they’re above the frame rails so the few problem nails we got couldn’t be pushed through.

Screws are the main problem. Since they have threads that grip the MDF and usually only going partway through the board, driving them through by force seems like it would just rip a huge hole out out, widening at the bottom. Something that might require replacing the entire table, so I’m not ok with directly experimenting on the table itself.

But not everything works out the way I picture it, of course. It’s possible to experiment on a sample of MDF glued together like the table and see how it works on a bench.

@dannym have you thought about the tiny hole saws? they have an ejection port so they should not get too clogged with waste:

or a plug cutter? Milescraft - 3-Piece PlugCutter Straight Plug Cutting Set

I did see both options. The Milwaukee is a tile grinder, a 1/4" OD diamond grit bit that isn’t effective on MDF. The plug cutter (anything without a centering drill like a hole saw) is a possible option. It looks like a larger OD hole size than ideal, but depth looks like the real problem.

The depth of a busted screw would vary, but if the spoilboard is up to 2.5" thick, if the bit can’t cut all the way through the spoil, there would be a ring say 1" deep cut around a screw busted 3/4" into the spoil but that don’t necessarily free the screw, especially if the ring is much larger than the screw shaft.

We could have spare full-thickness precut MDF plugs the size of whatever hole size is cut to glue in to patch it. But if a hole is cut with a plug cutter- which makes a ring- is not all all the way through, then there’s still a column of MDF standing there and it’s not free to plug. You could cut a partial-thickness ring around a screw (could do that with a long 1/8" endmill in the spindle too), try to tear the MDF out by prying it and broken screw with a flatblade screwdriver. The flatness of the bottom of the hole might present an issue for plugging.

I was just looking for a simple one-step- a hole saw/plug cutter that makes skinny holes up to 2.5" deep (maybe even more). They don’t seem to come in that aspect ratio, it might need to be hardened steel in that aspect ratio, thus the “hey this punch looks really close”, and they come in different sizes.

These Woodcraft screw extractors linked at the bottom here are close too, a toothed tube, you just chuck them in a cordless drill, but they’re limited to something like 1" depth, so I’m not sure that will work. Or maybe get thin-walled tubing from the hobby shop and Dremel some teeth in it. Dremel’ing teeth into the thin-walled hardened steel paper punch might rock. Emery cutting wheel can do hardened steel.

Other solution of course would be to use an endmill to just bore down into the screw with a carbide endmill. Hard on the endmill, and it can chatter pretty bad. Was hoping for a hole saw concept.

I was just at Asmbly and looked at the screws (I found 3). At least one is directly over the metal support rail so punching through won’t work. The best way to remove them is to drill around the screw with a plug cutter deep enough to grab the top with a needle nose vise grip and twist it back out. Unless there’s an objection, I can bring the tools in tomorrow or Friday and remove the screws.

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Thanks but it’s no rush, until we need to resurface again. I’d actually like to leave them for now to keep trying this paper punch concept.

The vise grips, we’ve tried, mixed results, mostly not good. Seems to require quite a lot of clearance gouged out it to get a good enough grip with the vise grips. I don’t see a way to know how much grip you need and if you don’t dig out for enough grip it can just round off what you started grabbing and have to gouge even deeper that you initially would have needed to then get a grip on what’s left.

If the vise cannot get enough grip to overcome the friction of the threads, drill a small hole next to the screw. This weakens the mdf between the screw and the hole. Then lever the screw toward the hole and the screw should loosen and be easier to remove with VERY tight vise grips. Leaves a bit of a mess but it’s easy to glue in a mdf plug.

Another option is to clamp a vertical drill guide over the screw. Then center punch the screw shaft and drill out the center of the screw. This destroys the screw and the remaining metal bits can be sucked out with a vacuum.

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I find that vice grips are ok at grabbing some of the screws in the table. I have have better luck with Irwin channel locks. The teeth are smaller and grip much better than most vice grips.