Hacker News Reader

Don't forget that an electric drill is insulated. So if you hit mains electricity (like I did last week) you just get a loud bang and a scare.

I know few guys who have gotten through 400v main with an excavator and just loud bang and scare. Those excavators are not insulated in any way, but the cockpit does make Faraday cage. I think they usually continue working after booting every on board computer and getting a new bucket.

The amount of insulation you need is minimal as the excavator blade/drill bit will work as conductor and most of the current then just follows the path it normally would. The flash and bang come from the short period of time when there is small air gap between the electric line and the tool being used and then that gap gets welded shut really fast.

The amount of insulation you need might well be reached with just wooden handles on the drill. Or wearing rubber sole shoes.

I would not take that chance. 400 V to 600 V is the real danger zone in electricity, high enough to do serious damage in a short time, low enough not to arc until it is much too late. Added to that that you're going to be sweaty and that soil conditions might give you good conductance that's an easy way to die.

The slowness has one more advantage: it's very hard to burn the sides of the hole with a hand powered tool. This can be important for instance when re-boring the hole for a pin in a piano pin block. If the wood burns during the boring the pin won't hold so going extremely slow and giving the wood time to cool is crucial to a good repair.

A very important advantage is that it's nearly impossible to get serious injury from manual drill. I played a lot with it as a child, doing some constructions and having a lot of fun. I don't think that it's safe to allow children to play with electric drill.

As a child and later manchild who has played with electric drills, I find it would be very difficult to injure yourself. You'd need to apply a lot of pressure to drill into yourself. You can somewhat safely touch the sides of a drill bit as it's spinning and it won't do anything.

Sore wrists though ... yeah I can see that. Those things vibrate a lot.

I guess you could cause the drill bit to fly out at high speed if you don't fasten it properly, but what kind of maniac drills with a wobbly drill bit?

True, but drill presses are actually quite dangerous. If they spin moderately fast (a few hundred rpm) and you drill into a steel object that is a few kilos and the drill grabs the piece it can throw the workpiece with lots of force if it isn't tied down well enough, and it takes a lot of tying down before it is 'well enough'.

Then there's the chance that the drill bit will shatter and bits come flying off at high speed. This can happen with a hand held power drill as well.

Ah yes I haven't played with drill presses yet. Well a little bit at shop class in middle school but that was soft wood.

Never had a drill bit shatter before. How do you achieve that? Does it require anything more than eye protection and long sleeves?

> How do you achieve that?

Hard metal, moderate vertical pressure, drill bit seizing deep in a hole. The remainder of the drill then has to absorb the energy in the gears and the motor, if the drill is hard enough it won't flex but it will break, and if you're unlucky it will break apart in many small pieces.

Eye protection is a minimum with any drill, long sleeves won't hurt. Setting things up so that if the bit shatters it is not going to have anything critical in the plane of rotation helps as well. I've had this happen only twice over 30 years but it's a pretty good surprise when it happens. Both times it was with large bits (20 mm and up), cutting oil and a deep hole in hard steel. That seems to be the perfect recipe. Even then the usual outcome of the bit seizing is the drill circuit protector kicking in before anything bad happens.

The large diameter means you'll be gearing down a lot in the drill so there will be a lot of torque available and as long as the bit is cutting you don't really notice that. I suspect that if you analyzed the problem in detail you'd find that some chip got wedged between the drill bit and the hole walls which would shorten the length of bit available to absorb the excess momentum.

Extracting the remainder of the drill from the hole can be quite an interesting challenge all by itself.

I've had burns from hot drill bits...

Surprisingly, you can generate enough heat with a hand drill to burn yourself on the bit.

The other standard drill injury is nigh impossible too. You know, the one that starts out by thinking "I don't need to clamp this". And ends with spinning the workpiece around and catching yourself or your hand.

As an added added bonus, you also probably won't find yourself tempted to chuck a wire wheel in a hand drill, which eliminates several other ways to damage stuff or yourself.

>Also, you can't crank in reverse. That usually just loosens the chuck

Get a drill or chuck that costs more than a couple of Big Macs

I'm not sure I understand your comment. The chucks on hand drills are pretty universally hand tightened. It isn't as though there's a chuck key to tighten it down until the bit screams for mercy :-)

I should probably clarify that you can usually get away with drilling in reverse for a little bit, but if the bit is truly stuck and you start twisting the drill around, you're pretty likely to end up loosening the chuck. Obviously, grabbing by the chuck and trying to twist the bit in reverse is a sure-fire way to loosen the chuck.

Because the crank is geared up, you don't get much torque cranking in reverse, so once you get a bit stuck, it quickly becomes a pain to get it free.

Who is this idiot who keeps getting drill bits stuck, you ask? It's actually pretty easy with some bits. I have a set of DeWalt bits that cuts far too aggressively in softwood. Especially as you're exiting a hole, the cutting edges will feed though without fully clearing the hole, and the remaining wood will engage the flutes and pull the bit in like a screw. This usually also compresses the wood into the flutes as well, and just makes for a real mess.

With an electric drill, you can (if you don't care about the back side of the board) pull backwards on the drill and gun it, and let the edges of the flutes clear (tear out) the bits of wood engaging them. Not really an option with a hand drill.

What I usually do with a hand drill is to pull back and crank normally; the bit comes out easily, pulling back keeps it from going deeper, and it also removes the swarf in the hole cleanly.

Come to think of it - I do this with electric drills, too (and you pretty much have to with a drill press). So now I wonder:

Why is everybody switching their drill in reverse to back out the bit - this shouldn't be necessary!

The only time I've used reverse in an electric drill was when I was using it to drive (remove) screws (variable speed drill of course). I think for certain materials you have to run a standard bit in reverse to drill them properly (for some reason, I'm thinking glass, or ceramic tiles?)...

Also, you can't crank in reverse. That usually just loosens the chuck.

This may seem like a dumb question, since I've not used one of these before, but isn't that what the other gear on the shaft near the top (on those which have it) is for, to provide a reverse gear?

The top gear is just a "follower", to balance the forces on the body of the drill and keep load off the bearing in the centre. It doesn't drive anything. To drill backwards you .. turn the handle the other way.

The problem is the screw in the chuck getting unscrewed, because all the parts are on the same shaft.