World's Smallest Drill Hole

That seems small for a survey point, and probably gave great joy on finding it in that messy area.

But if there's a prize for smallest I can do better than 0.01 ft ~1/8" ~3 mm.

@bill93?ÿ

Anything smaller would be a pin hole.

I've used 2.5mm. on concrete surfaces where heavy abrasion is likely and any normal marker would get dragged out.

2.5mm. drill hole, to about 20mm depth, shallow 4.5mm countersink, then drive a 3mm. stainless steel countersunk head screw into the hole. If you leave the drill dust around the hole and push it in as the screw gets hammered down it'll bind and stay forever. Just make certain the head is just below the surface. I've occasionally found some that I put in 30 years ago, still resisting the efforts of snowploughs!

I had a teacher in high school who was retired from the Navy.?ÿ After WWII he had been stationed in Japan.?ÿ He was a mechanical engineer and worked with Japanese industry during the reconstruction.?ÿ There was a "friendly" rivalry between a Japanese tool company and an American company over who made the best tools.?ÿ One of the competitions was for who could make the smallest drill bit.?ÿ He said the American company sent over a tiny drill bit - the Japanese firm sent it back with a hole drilled in it.

Mr. Rivers developed a great respect for the Japanese people during his years there after the war.?ÿ He was also a good math teacher and a strict disciplinarian.?ÿ He would be in big trouble in our schools today.

Andy

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Posted by: @andy-bruner

He said the American company sent over a tiny drill bit - the Japanese firm sent it back with a hole drilled in it.

nice.

@chris-mills?ÿ

Curious why you hammer in a screw rather than use a masonry screw (not many that short I've seen through) or a tap in masonry anchors like the Ramset Shuredrives?

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In NZ the tap in ones are the go to for control points in concrete. Personally, I try to counter sink them by running the drill bit around the top of the hole at 45?ø. Also if you use the ones with the stainless nail you can use a punch to make a fine dimple on it as the reference point.

@andy-bruner?ÿ

My father told me the same kind of story.?ÿ At Snopes they rate it as "legends"

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Here is the one dad repeated to me:

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"As it was being told just prior to World?ÿWar II,?ÿa German manufacturer had asked an American steel company to produce a?ÿ4-foot?ÿsample of the thinnest wire they could make. The Americans put their most experienced metallurgists and wire-drawers on the job, finally producing what they believed to be a work of technological art. A special courier was dispatched to Germany to deliver the sample and get the reactions of those it had been made for.

The courier was welcomed at the plant and given a glass of schnapps while the wire was taken to another room to be examined by German experts. Before the man had finished his drink, the box heƒ??d brought the sample in was returned to him, now sealed with wax. ƒ??Your answer is in the box,ƒ? he was told. ƒ??Please do not open it until you return to your plant.ƒ?

Stateside once more, the wire was examined by the American engineers whoƒ??d slaved over it. They found a hole drilled down its center, effectively turning their solid thin wire into an impossibly-reamed hollow tube."

Posted by: @andy-bruner

One of the competitions was for who could make the smallest drill bit.?ÿ

There's a YouTube video I saw a few years ago showing a competition between two machinists to see who could drill a hole longitudinally through a 0.5 mm pencil lead.?ÿ One guy was using a manual toolroom lathe with a tiny (!) twist drill bit, the other guy used a wire EDM (electric discharge machining).?ÿ As I recall, the lathe approach came closest to succeeding (and may have actually succeeded). I think the EDM kept burning through the side of the lead.?ÿ?ÿ

What this reminds me of is the whole business of US survey foot vs. international foot was supposedly created by a need in precision machinery to have an inch that was so well defined that the differences among US, UK, Canadian, South African, and Australian definitions of the inch were making a difference, and a supposedly interchangeable part made to the standards in one country would not necessarily interchange with the same part made in another country. Supposedly this kind of problem first became noticeable during World War II.

But I have never been able to pin down any specific information to back up this vague idea.

Units are decidedly weird things.?ÿ Take the ton for example.?ÿ Long ton, short ton, water ton, freight ton, ad infinitum.?ÿ A freight ton is 40 cubic feet.?ÿ A ton of air conditioning provides the same amount of cooling as one ton of ice melting.?ÿ Still not sure what a 3/4-ton truck is, though.

https://en.wikipedia.org/wiki/Ton

I will be happy to convert the drill hole's diameter to what ever units you desire... except tons.

Posted by: @holy-cow

A ton of air conditioning provides the same amount of cooling as one ton of ice melting.

Not quite-it's a rate, not an amount..?ÿ A ton of air conditioning removes heat at a rate corresponding to one ton of ice melting PER DAY.

You are correct.?ÿ As usual.?ÿ Thanks.?ÿ I needed that.

Posted by: @lukenz

@chris-mills?ÿ

Curious why you hammer in a screw rather than use a masonry screw (not many that short I've seen through) or a tap in masonry anchors like the Ramset Shuredrives?

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In NZ the tap in ones are the go to for control points in concrete. Personally, I try to counter sink them by running the drill bit around the top of the hole at 45?ø. Also if you use the ones with the stainless nail you can use a punch to make a fine dimple on it as the reference point.

Sorry for delay in replying - it's been Platinum Jubilee weekend over here, so a four day holiday.

As you say - length. I said screw, but they are actually 6mm (or occasionally 4mm) crossheaded bolts. Drilling larger holes and then plugging is a bit of a waste of time for points in a horizontal surface (I'd always use plug anchors drilled horizontally for level points) and you can't easily screw into concrete so hammering into a hole just sluightly smaller works wonders.

I'll countersink if there is a serious risk of them being scraped out by a machine, but then you can't level accurately off them (but OK for putting the rod tip onto the cross). For levelling I'll use the type which have a rounded head rather than a countersunk. They only stick up about 4mm. and are much easier to find when there's a bit of muck covering them.

They are all A2 stainless. For macadam surfaces I use coach bolts - 60, 75 or 100mm long (that's 2,3,4 inches?ÿ in English). They are A4 grade and will withstand anything, especially centre punches and hacksaws. I had to get some special punches made in order to mark them and it needs a 7lb hammer to do the job. (8mm. shanks, drill macadam with 7mm. drill).

What's the purpose of this drillhole??ÿ If it's a traverse/control point, no problem.?ÿ?ÿ But if it's a monument for a lot corner or something, then it's pitiful.?ÿ Should be at least a 3/8 or 1/2" minimum, drilled till the bit will stand on its own

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Posted by: @jph

What's the purpose of this drillhole??ÿ If it's a traverse/control point, no problem.?ÿ?ÿ But if it's a monument for a lot corner or something, then it's pitiful.?ÿ Should be at least a 3/8 or 1/2" minimum, drilled till the bit will stand on its own

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As described; those are traverse stations, although they should last until the concrete is destroyed. For longer lasting ones in concrete I use the coachbolts typically 8mm. diameter and 100mm .long. Again, once set they will only go if the concrete itself is destroyed.

And you can't guard against ignorance - many years ago I was on a site one Monday morning when the muckshift supervisor staggered in with a wheelbarrow in which lay several large chunks of concrete - "these were going to get damaged" says he, "so I put them carefully to one side". All marks undamaged!!

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