Hi guys. I was just doing something and i need to drill a hole that is over 500mm deep. The thing is, also need it to be thin (about 5mm in diameter). To my knowledge, there are drill bits that can be longer than usual at hardware stores, but they are usually too wide for my purposes.

With this being said, how do i drill this really long hole?

Also, if i drill a long hole, are there any problems i might encounter (such as the hole not being straight, etc). I dont have a drill press by the way, im just using a regular power drill.

You may be able to find a 500mm long drill bit with a 5 mm diameter.

Failing that, find a bit as long as you can and try drilling from both ends.

As for it being a wonky hole...That's a definite possibility using a hand drill. Line it up as well as you can and drill slowly and keep it as straight as possible.

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Failing being able to find one.

Get 5mm bit + 5mm rod and..err do you have a lathe? lol Thread inside drill bit, and thread end of rod. Just like the oil rigs.

Or possibly just weld rod to drill bit and then clean down the weld so it's nice and uniform with drill bit.

cant find a really long drill bit thats thin, and i dont think i can drill on both ends because they might not perfectly meet (a slight variation in angle might fuck the whole thing up. Besides, the longest 5mm drill bit i have still isnt long enough.

rather than welding the drillbit to a rod, i am thinking of epoxy resin, and using a low speed. The strength of the join shouldnt matter, as the adhesive/weld only needs to turn the drill bit. otherwise, the weight of the drill and the walls of the hole themselves should keep it in place.

ill try this tomorrow, but i fear that a rod isnt "twisted" like a drillbit. so it might not be able to remove debris and stuff properly, thereby making it unable to go deeper than where the twist ends

Shouldn't matter too much.

EDIT: I stand corrected.

I don't quite understand what you mean. Turning the bit is what takes the most force. How are you going to put them together when you epoxy them?
Also, what kind of wood are you drilling through?

Since the entire shaft won't have flutes you'll have to pull the whole thing out after drilling a couple inches to clean the debris out.

I really doubt that simply epoxy would work. Find someone to weld the rod and bit together, or failing that, drill a hole in both rods, and thread it, or epoxy a tinier longish rod in between the two. More surface area that way. Epoxy has a high tensile strength, but its also very brittle, so it can't absorb sudden impacts like a weld can.

In any case you won't be able to drill in one go as mentioned b/c of the threads, so drill a short distance, then pull the bit out of the piece you're working on to get rid of the chips. Otherwise the bit'll just jam and you'll be fucked.

If you saw the bit down at the top so the grooves empty out up top, and use a less than 5 mm rod you'd have space for the chips to exit, however a thinner rod would probably be harder to keep straight.

You're biggest problem though is getting it to go straight. Without a drill press I say clamp the piece down on a bench, and clamp something like a washer or nut down in front. Run the rod through the washer and use the washer to keep the bit aligned.

Don't listen to dumbasses telling you to drill a hole in another drill bit, that's just dumb.

Drill a hole with your 5mm drill bit till it will go no further. Then find a iron/steel rod about 5mm in diameter, sharpen the tip and cut it to about 600mm.

Use it like a drill bit. Should be ok if you are drilling woods. Once tiny hole starts to appear on the other side, switch back to drill bit and drill from the other end.

Would that really work though? Even a small bit without a place to eject chips gets jammed. Horribly.

Now, take, say a 4 mm bar, flatten the tip with a hammer so its wider than the rod, and sharpen that into a spade. I can see that working.

That would be smart if precision is not something you are looking for. But if you want it to be nice, use a 5mm rod and go slowly, very slowly so it will not overheat.

Oh, and sharpen the steel rod symmetrically just like a drill bit so in the end it'll look like a sharpened flathead with a diamond shaped tip.