Does a 2" (5 cm) cutting depth 1/16" (1.6 mm) drill bit even exist? If not, is there any way for me to make this hole? I'm drilling a fiberglass/foam sandwich if it matters, and I want to make a hundred holes. My cheap standard drill bits cut the fiberglass just fine, but are half the length I need. And yes, I'm aware that the reason they're kept short is so they don't break all the time.

This probably sounds weird – it's for installing a starlight ceiling effect in a fiberglass float tank.

  • Your drill bits are only 1" long?
    – mbeckish
    Feb 1, 2016 at 13:43
  • 2
    @mbeckish Most bits as small as 1/16" diameter are pretty short. Standard ones are probably no more than 1-1/2". Feb 1, 2016 at 17:05

4 Answers 4


A quick visit to a metalworking supplier website finds 3" long (overall length) ones with 1.7" cutting depth (presumably the flute depth, so for light-duty drilling if you "peck" (pull out to clear chips) when you get deep you could probably get it done. "Extended-Reach Drill Bits" A more extensive search might find a longer one. Buy them by the dozen, you probably will break some and they are usually cheaper that way.

A different metalworking supplier website has 6" and 12" OAL listed (under "aircraft drills" which the other site calls "Short-Flute Extended-Reach Drill Bits") but only 7/8" flutes, which would be a lot more pecking to get the chips out.

  • 2
    Friend of mine was an A&P (aircraft) mechanic, and he always had a ton of these thin, long drill bits. They were also very good quality and would last much longer than anything at a home store.
    – JPhi1618
    Feb 1, 2016 at 15:32

This is more of a shopping question. I just looked before I answered the question and I have two 1/16" bits at around 3-4 inches (sorry too lazy to get the tape out). Put them in your drill with 2 inches sticking out and drill. Will they break? Maybe. You will only break them because you are trying to do it too quick. You are drilling really nothing, so it is you jerking the drill weirdly that will break the bit.


Presuming you can find long enough bits (you can), and presuming you don't want the pointy ends of your drill chuck scraping and boring your fiberglass, you want to use a drill depth stop. You'll slide this onto the bit to the exact depth you want, tighten the set screw, then drill.

If you're extremely concerned about drilling perfectly perpendicular holes, then use a plunge base on a router with a drilling bit. The plunge base will let you set the exact depth.

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This is an old post, but the correct way to do this is to drill larger holes (1/4 inch would be enough if there is enough space between holes) from the back side of the part, then drill the 1/16th holes in the same positions from the font side.

  • This is not answering the question asked - 1/4" was never mentioned. Jun 29, 2018 at 14:55
  • It may not answer the direct question of how to drill a 2inch deep x 1/16th inch diameter hole, but it solves the actual problem. Engineering often requires creative manufacturing solutions to achieve an equivalent result. Telling someone how to properly achieve an end result can be far more valuable than explaining how to do it the hard way.
    – Jimbo
    Feb 15, 2019 at 22:37

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