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What technique do I need to use for drilling out a steel screw? Might be stainless, not sure.

I'm using a Milwaukee M18Fuel hand drill and Milwaukee cobalt bits. It's a powerful drill.

I've made a mark with a center punch and am using a moderate amount of pressure. I drill for ~10 seconds and let the drill rest for 20. I put a drop of thread cutting oil on the screw every other time. I'm using the slower "1" setting on the drill. Problem is, it seems to be taking FOREVER and I'm not sure if I'm doing something wrong. Don't want to damage the drill or destroy all my bits.

BTW, I've tried everything before deciding to drill the screw but everything failed: impact driver, impact screwdriver, vice grips, all the stuff that gets repeated on the web. Nothing worked. The screw is stuck. I think this is a self-drilling screw. This is to gain access to a junction box that the previous homeowner screwed shut for some unknown reason. Don't care about damaging the junction box cover.

Thanks

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    What is the diameter of the screw and the drill bit you're using?
    – TooTea
    Commented Sep 7, 2021 at 19:42
  • Do you want to remove screw head to remove something or need to remove body of screw from hole? If just the screw head, would suggest an angle grinder. Grind head off and pop cover/something off.
    – crip659
    Commented Sep 7, 2021 at 22:58
  • The diameter of the screw head is 5/16". I started out with a small 1/16" bit and have worked my way up to 3/16". It just seems like they're cutting extremely slowly so I wanted to know if there was some technique that I was doing wrong. I've only really drilled wood before.
    – Dan
    Commented Sep 8, 2021 at 0:08
  • @crip659, I just need to get the door to be able to open (the screws are holding the door shut). If removing the head alone is sufficient then that's all I need to do. I don't have an angle grinder and my dremel recently broke. I'll look into buying one.
    – Dan
    Commented Sep 8, 2021 at 0:13
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    "It just seems like they're cutting extremely slowly" - then you're doing it correctly. Keep going as long as it's making chips. Use a corded drill with a handle, set as slow as possible but fast enough to not instantly stall. Push hard until it stalls, then back off a little. It could be work-hardened at this point and you will need a fresh bit, after you sacrifice another fresh bit to get past the hardening. "It's a powerful drill." - Too powerful and too fast. $40 variable speed corded drill with a handle = perfect.
    – Mazura
    Commented Sep 8, 2021 at 13:43

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A few techniques I've used successfully and depending on the materials and geometry of the situation.

-For the hardest materials, grinding is better than drilling (stainless steel is pretty hard to drill)

-Use a Dremel tool to cut a slot in the broken fastener shank and then use a screwdriver to back out the broken off fastener

-Use a Dremel tool with an appropriate burr or grinding type bit and grind out the broken off fastener; you will likely have to re-tap the hole before reusing

-Remove enough of the broken off fastener and then perhaps the retained cover, and then use vice grips to back out the broken off fastener

-(For softer metals and relatively larger diameters) Use a left-handed drill bit and sometimes the fastener will back itself out while drilling. If not, after drilling to a depth of about 3x-5x the bit diameter, use an appropriately sized screw extractor - be VERY careful so as to not break off the extractor since its hardness is very hard and almost impossible to drill

-I haven't tried this myself since I don't have welding equipment, tack a donor bolt to the broken fastener and back it out

Be prepared to buy multiples of the grinding items as they will be consumed.

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  • Screw extractor already failed. I doubt I'd be able to back it out with a slot. Even before one of the screw heads was damaged, it didn't budge with my M18 impact wrench at the highest setting. So you suggest grinding the head off basically?
    – Dan
    Commented Sep 8, 2021 at 2:23
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    @Dan K So it seems you must abandon re-use of this broken fastener's hole and use a grinding or cut-off technique to remove the head so you can remove the cover. A Dremel tool will do the job with the right bit (and minimize incidental damage with a steady hand).
    – coderjohn
    Commented Sep 8, 2021 at 2:31

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