Load it up with a compass and you’ll have yourself a classroom war

You joke but here is the Tomahawk Angle Trisector It trisects angles.

“Aye sir, where can I buy one of them math crossbows?

x-bow

Weapon of math instruction

My comment cannot improve upon your excellence, but I felt like I had to say something. Well done, sir.

I laughed until my both sides hurt. Chef's Kiss This comment.

Grinds my gears that some people don’t get this. Sent my mate a picture of my newly assembled 3018 Chinese mini cnc and he goes “what’s the plan with it?”. I don’t fucking know mate I’ll think of something. I ended up drawing a cock and balls on paper, photographing it, tracing it in Inkscape, then having the cnc engrave it on a Lidl ham chopping board. Happy now lad? A plan, executed.

Edit someone asked so here it is:

https://pasteboard.co/JPNJgtj.jpg

Someone else asked what I think. I bought the cheapest one, I can’t remember the brand. I got the 5.5mw laser too. For the price (£170?) it’s pretty good. It takes a fair bit of work to get it running and it’s not as well supported online as the ender I’ve got so expect to troubleshoot on your own a fair bit. But not hard. The chassis is surprisingly well made, in that it’s all cut square and goes together well. You need to deburr everything but hey it’s dirt cheap. You will need to fettle to eliminate binding but no bother. I suspect they’re identical whichever brand you buy, although perhaps better quality stepper motors - mine don’t seem great but whatever. I’m not sure the laser is worth it - I can’t get it to focus properly but I haven’t really tried much yet, maybe sack the laser, get to know it, and just buy a better laser separately? The spindle motor will definitely get upgraded, although I think you can feed it 36v fine so I might try that first (supplied power block is 24v). Overall, excellent craic highly recommended. Also I 3D printed a pen holder for it so I can also draw cock and balls with a biro on things now too. I alsoOrdered a random selection of cutters up to 7mm end mill, that will be amusing to to try out.

Can one buy this to measure the radius of another’s asscheeks?

r/nostupidquestions

As an electrician, I would kill for this to measure cable bend radii. The tools we have at the shop are literally premeasured quarter pie pieces of metal.

Measure the arc of dat ass and see how much it will take to reach the centre point.

Fitting things to round things, of course!

Bring it out at parties.

So do I. Do you know where I can find one?

Seems like you would use it to measure a radius

I need this for measuring guitar fretboards

He is best known for being the first person to calculate the circumference of the Earth, which he did by using the extensive survey results he could access in his role at the Library; his calculation was remarkably accurate. Eratosthenes

à la explainxkcd

I can't seem to keep his name in memory.

We all know that most people would use this to help measure girth

I was wondering exacly the same ahaha Even if the tool is super accurate i’m not sure two people will get the same measurement

You calibrate it by setting it on the floor and seeing if it measures the Earth correctly.

Yeah, I didn’t see any way to ensure the measuring portion is parallel to the circle/arc. Being slightly askew would cause an inaccurate reading.

Pro-tip: if you want to measure <thingy> just google <thingy> gauge. Engineers and scientists have measured virtually everything, and will generally sell you a doohickey to make it easier.

There are probably even tools out there for measuring your thingy, if that's you're thing.

No, I'm pretty sure you could set them up to measure a curve and have it fail if it was out of tolerance.

https://imgur.com/gallery/sLUms1U

Arc length is not fixed in this gadget - you can see the little slides on the feet. The metal bow is only there for a visual reference (and for marking other objects).

This is simply defining a three point circle, with the linkage hooked up to produce a linear motion as it moves. The scale is arbitrary, and depends on the specific linkage being used.

"Magic... Got it."

Yes, you explained the basics of measuring arc length and radii. But this isn't how this contraption works at all.

I don’t think arc length is fixed.

I read all of this in Sal Khan's voice.

Alright nerd, let's fight

I don't understand your magics, bur we're fighting

Aaah, so you use it to find the radius of a circle. Now I get it. I was wondering what was it used for.

^ doing the lord's work

Right? As a machinist I can get you that radius to within three decimals.

SIN COS TAN

the three most frightening buttons in existence

It's measuring radius by measuring the curvature of the edge.

Imagine the curve it's measuring is part of an invisible circle where that curve fits on the perimeter of that circle. It measures the radius of that invisible circle. The markings on the device have been pre-calculated to convert that curvature to a radius.

This allows you to get the radius of a curve even when there is no complete circle.

I’m sure you could determine several qualities of a circle with this device, radius included.

If you know 3 points in a circle (or arc) you can know its diameter/radius.

Its what that tool does. It has 1 fixed point in the middle and 2 on the sides that move (the tool also has a band that goes through those 3 points to help with the measurement but technically its not needed)

The people that invented that tool calculated the ratio between the movement of the two front arms and the 2 back ones that are connected to the lever and how they relate to a circles diameter and printed the scale accordingly

Probably not very accurate if you're looking for high tolerances, but for most workshops its quick and good enough

If you know one you can calculate the other.

It literally shows in the video “radius in inches.” It indirectly measures the radius by directly measuring the arc.

sure it does.

arclength / inner angle = circumference / 2pi = 2piR / 2pi = R

arclength is usually L or s depending on contect, angle T (for theta).

L/T = R or L = TR.

the magic happens when any one variable is fixed. L is fixed, obviously in the video because its the metal band flexing that never changes length. therefore as the band flexes inwards, L = TR creates a relationship where the angle and the radius are inversely proportional. you only need to know one value, say the angle (as is the case in the video) and the radius is forced.

Your confidence is sorely misplaced.

It does measure the radius, you can see as much in the video as the measurement it gives is labelled as radius, in inches on one side and millimeters on the other.

This tool has no way to measure degrees of arc. This tool is completely agnostic to whether you're even holding it up to a circular arc or a complete circle.

It's called in outside radius gauge because it measure a radius from the outside of the arc. To measure it from the inside, the arms would have to bend to opposite way. Such a tool also exists, called an "inside radius gauge". Both tools are used to measure the radius of an arc or a circle.

It doesn't "measure the arc in radii", because radii isn't a unit of measure, it's the plural of radius. You're probably thinking of *radians*, which is a unit of measure of angles. While relevant to arcs, it wouldn't be measured directly with this tool.

If you know a circle’s curvature then you know it’s radius.

Yes, they are called inside radius gauges. They look very similar.

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My guess is to place the piece on a worktable. Then clamp 90 degree stops (I think 9 of them) to the inside radius of the pipe.

Not that small, petal.

150 mm from the looks of it.

I work in an industry with a lot of precision tubular parts and haven’t actually seen one of these before. At my facility, Quality Control has a few micrometer sets to measure outer and inner diameters of parts. I’m not sure what they use for the really big stuff (>24”), maybe the big digital caliper. We also have a couple of Pi Tapes.

E: just realized you said radius specifically. They have a special caliper for measuring radius, as well as some radius gauges. Probably some other clever stuff too.

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Imagine you need to replicate a section of handrail, but don't know how far to bend it to get the right shape. This tool will give you the info you need to do that, especially if you need repeatability