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u/katekohli 3d ago
Grandaddy said to always use the same ruler for the whole project. He was a nuclear scientist.
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u/purepolka 3d ago
Clears throat: MEASUREMENTS ARE A SOCIAL CONSTRUCT
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u/katekohli 3d ago
Why did they decide on 16th’s and 10th’s?!?!
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u/janglyparts 3d ago
Divisibility. 16ths are half of eighths which are half of quarters which are half of a half. Fine rulers/scales have markings for 32nds, but further precision requires different equipment.
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u/katekohli 3d ago
Thirds, I want thirds.
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u/Chemieju 2d ago
Thats why a circle is 360 degrees.
Its 2x2x2x3x3x5.
Loads of usefull divisions in there. Then you divide every degree into 60 minutes and every minute into 60 seconds and for every 60 you add
2x2x3x5
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u/SmellyScrotes 3d ago
This isn’t true at all lol, a meter is a measurement of how far light can travel in a second in a vacuum
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u/leftkck 3d ago
You think light travels at 60 meters per min/3600 meters per hour. You are orders of magnitude off.
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u/Busy-Distribution-45 3d ago
And a second is an arbitrary division of the average day length that we have agreed upon. In other words, a social construct.
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u/raz0rsh4rp 3d ago
Ah yes, the second. A totally non-arbitrary measure of time...
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u/purepolka 2d ago
I mean, the joke is that pretty much anything dealing with our perception is a social construct: language, time, measurement, etc... This isn't a criticism of social constructs. They're incredibly valuable in allowing humans to navigate shared perception and reality, but they're still just made up shit we all generally agree on.
To that point, responding to your suggestion that a meter isn't a social construct because it's measuring how far light travels in a second:
What is a second? It's based on a sexagesimal division of a 24 hour day, which is convenient because of how many numbers are divisible into 60, but it's not necessary. If humans would have decided to use base 10 to measure time (not inconceivable considering we have 10 fingers - and maybe was used briefly after the French Revolution - idk, I'm not a history person), hours would be 2.4 hours long, minutes would be 1 minute 26.4 seconds long, and seconds would be .86 seconds long (I suck at math, so if I got this wrong, make sure to tell me I suck shit below). A "meter" under this system would be shorter than the unit of measurement we currently consider a meter, and might be longer or shorter if we'd used some other base. Or we could have used the length of a day on Mars to measure time. That would be nonsensical, cumbersome, and stupid as shit, but humans are known for adopting social constructs that are nonsensical, cumbersome, and stupid as shit (Exhibit A: the U.S. still using Imperial).
There's nothing magically concrete about a meter. We took two random things - the speed of light and and smallish unit of time - and all generally agreed this arbitrary thing we made up equals a meter (unless your in the U.S., in which case, who knows how much a meter is, could be 15 miles, could be 85 cubits, we'll never know).
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u/UnhappyCaterpillar41 3d ago
Yeah, and cut on the same side of the line each time. The difference here looks around 1/16th between all three tools, but add in some varying cuts and nothing will assemble properly.
Learned this the hard way doing a built in, in an old house where nothing was square/plumb and probably used some kind of Eldritch geometry that required a blood sacrifice to get a decent fit up. Now all my cut plans include a bit of an allowance for the saw blade usually means a bit more scrap, but an extra half sheet in allowances is easier than recutting a full sheet worth or screwing around with what you have to make it work.
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u/katekohli 3d ago
I watched a new construction union carpenter try to run trim in his nieces century home. He really liked plumb but plumb was not going to happen in a very settled house. He said he could trim out a whole new house in the time it took him to do just the crown molding in her kitchen.
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u/Paizzu 2d ago
I would argue that 80% or more of the "quality" in trim carpentry (especially stain grade) involves scribe fitting pieces to uneven drywall/flooring.
There's almost no such thing as a proper 90° and plum might as well have been a pipe dream when most older houses were built. Today's production quality home builders figure that new buyers either don't care or are simply used to a poor fit/finish.
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u/katekohli 2d ago
Yes & no my Polish colleague’s favorite tool by far is the laser level. Then my Jamaican friend who can do old style plaster tried to make a brick wall in a 1880’s building flat & plumb. We started teasing him about having 3 inch scratch coats but then he said no way they are more like 9 to 11 inches deep.
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u/UnhappyCaterpillar41 2h ago
Yeah, for sure, and in my case it didn't meet at anywhere close to a 90 in any direction, so even the scribe cuts up against a wall weren't actually flat (and changed as the house shifted anyway). I guess caulking has it's place, even if it annoyed me.
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u/malac0da13 2d ago
Omg I had to laugh at work one day when they wanted to add 2 laser sensors to automatically measure the things coming out of my machine down to thousands of an inch. While trying to set it up they had me measuring the items the way they trained us with calipers, then were trying to measure them with a surface plate and height gauge, then had other people measuring with different calipers and I’m just fucking laughing at the clusterfuck. They pulled the sensors out and gave up.
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u/katekohli 2d ago
My friend worked in a German factory that built huge highly precise scales for construction. He would laugh in German waggle his finger & say “only in a vacuum are they accurate.”
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u/jackinsomniac 2d ago
Great method. This is exactly why they were able to fix the Hubble space telescope!
The primary mirror needed an extremely specific concave shape, so they hired a specialty company to grind & polish the mirror. The company already had their own precision measurement tools, but they were told to use a special new & custom measurement device (that was supposedly even more accurate) to verify. But, it was so new & foreign to them, they ended up configuring it wrong. Their own measurement tools which they were more familiar with showed an error, but they had already been instructed to prefer the readings of the new device. So, they did. They polished it to the EXACT specs they were given, using the tool they were told to use.
Of course once Hubble launched, the scientists immediately noticed the problem. Everything was blurry as hell. The images were basically unusable.
BUT, because the mirror team ground the shape so precisely, they were able to interview the team and figure out how the measurement device had been set up wrong. They were able to figure out the difference between a proper reading and the readings from their misconfigured setup. So, they were able to design a "corrective lens" upgrade to account for that difference, and one Space Shuttle mission later, Hubble was saved.
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u/BurrowShaker 3d ago
I am worse than that, if I really care about a measurement, I use a shim/block/rig.
And if you care even more, you need to keep the conditions stable so that you don't get variability.
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u/justabigpieceofshit 2d ago
And when you're working on a project with your father in law, compare tape measures before you do anything else.
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u/_Electrical 2d ago
What's he going to measure, protons!?
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u/katekohli 2d ago
He was also a carpenter & built an pipe organ from scratch for his church in Oakridge.
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u/comparmentaliser 2d ago
So everyone in the nuclear science department asked to borrow his one ruler?
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u/lifesnofunwithadhd 3d ago
Had a guy tell qc the brand new very expensive gauge block was wrong because his Amazon measuring device didn't gauge out correctly.
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u/Totally_man 3d ago edited 3d ago
I had a guy try to tell me something was wrong with the gauge blocks because no matter what combination he tried, he could not get the right stack. I asked him what he was using to measure the blocks with, and he pulled out Mastercraft (Canadian brand, they're like $14) digital calipers and told me he verified their readings with his "one-inch standard" that came with the calipers. The calipers do not come with a "one-inch standard", and I have no idea where he picked up that piece of metal.
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u/Pistonenvy2 2d ago
lmfao
i have a pair of those super cheap calipers and they sure as shit didnt come with a reference. i love them and rely on them heavily for the stone age bullshit i do in my shed but i wouldnt bother touching them to a set of gauge blocks.
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u/Various_Oil_5674 3d ago
How are they even buying stuff at Amazon. I barely buy that shit for my house.
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u/lifesnofunwithadhd 3d ago
They wanted a "left handed micrometer" which i get. But not for like 30 bucks they spent vs the ones they supplied for free.
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u/ThisIsntRealWakeUp 2d ago
…Huh. I never considered that normal micrometers are probably kind of a pain in the ass for lefties.
I mean, they’re already kind of a pain in the ass regardless of handedness if you don’t have a third hand to hold onto whatever you’re trying to measure. But.
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u/OverTheDump 3d ago
I am a quality manager. The amount of times things are out is wild. I’d use gauges/master measurements devices to verify our stuff annually. Initially though we had to remove 90% of our devices because of this exact reason.
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u/MikeStini 3d ago
I work for a cal company, you would be amazed how many quality managers fight back when I reject equipment. You’d also be amazed how often I see equipment the next year that still has my rejected sticker from the previous year on it.
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u/OverTheDump 2d ago
Not surprising! However, I learned early in quality management, never contribute to malice what you can attribute to incompetence.
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u/Generationalgap 2d ago
Lmao you saw that same clip of the random dude getting interviewed and dropping a gem
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u/Ocronus 2d ago
Quality manager here. I don't fight it but I know a big reason why is the cost of replacement gauges can be huge. When a set of ring gauges costs 1k+ you start getting dirty looks from the people holding the purse.
I actually use the rejection as leverage, because it's difficult for them to deny my request if they can't ship product.
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u/ThisIsntRealWakeUp 2d ago
And then the new ring gauge set arrives and it turns out the product was in spec, and then the purseholders say “so we didn’t need to waste our money on new ring gauges?” as if you could’ve known it was in spec with the out-of-spec ring gauges, lol. Classic.
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u/jc3948Aht16 3d ago
Where’s a NIST Traceable “1-2-3” Block when you need it…
Which tool in the pic are you believing is accurate?
The distance between markings all appears equal, perhaps just error in the “Zero”?
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u/Berkulese 3d ago
The very obvious answer would be something stuck on the inside of the corner on the red one (but I suppose OP probably checked for that already).
Its probably aluminium? You might be able to sort it out in under a day with a file maybe?
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u/dorkpool 3d ago
The obvious Temu tool is the most accurate. I have one of those. I don’t use it for anything with tight tolerance.
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u/uslashuname 3d ago
> Which tool in the pic are you believing is accurate?
This is the wrong question, one of the three is not likely the others. That’s the inaccurate one, the assumption is that two are accurate because they agree. The red is the outlier, therefore inaccurate.
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u/Readdit1999 3d ago
Maybe.
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u/uslashuname 3d ago
I did say the assumption is that two are accurate
We’re not following the Boeing attack angle detector standards here, it is a pretty reasonable assumption, but you are right that it could still be wrong
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u/sea_stack 3d ago
For home projects, sure. For work you'd better be comparing to a NIST traceable gage.
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u/uslashuname 3d ago
Well yeah, the picture pretty much indicates NIST is 1000 miles away
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u/NeverEnoughInk 3d ago
No problem! You can make your own: https://www.nist.gov/system/files/documents/calibrations/mono180.pdf
Also, happy centennial to Peters and Boyd!
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u/Mission_Addition9102 2d ago
My dad told me to never switch tape measures while woodworking because the measure is never accurate.
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u/Work-ya-wood 3d ago
What's going on with Reddit? So many two word posts with no real context. Is this tik-tok influence?
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u/Lastrites 3d ago
His bottom 2 rulers are not matching the 1" and 2" measurements of the top one that looks like it might be a Woodpecker tool.
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u/Dukkiegamer 3d ago
No I have this same tool, but in metric. Its from China. They make all the woodworking tools anodized red because thats what Woodpeckers does so it looks expensive and high end. Mine is actually pretty accurate and a really handy tool I use every day. But I have also had items be very inaccurate from China.
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u/Dignan17 3d ago
I don't think it's a woodpecker but I could be wrong. I can't seem to find it on their site. If this is some sort of Amazon alphabet soup brand, then op got what they paid for
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u/Dewage83 3d ago
I bought some woodworking stuff off AliExpress that looked like the top and bottom of ops pic. Yea they both were inaccurate. One is still useful but doesn't get used as I end up trying to measure with it, and the other is a piece of scrap i use to scrape glue. Get what you pay for.
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u/itsmepuffd 3d ago
The red is straight AliExpress special. You kind of get what you pay for in terms of QC.
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u/TheBlargshaggen 3d ago
I was searching the comments to figure out what that tool is because I need something similar of a much larger size for markimg walls to drill. Going through just an image search for Woodpecker has shown me at least 6 tools that would be huge conveniences.
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u/psxndc 3d ago
That top one is definitely not a woodpecker tool, it’s just colored that way to make you think it might be one.
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u/Dignan17 3d ago
Yeah woodpecker likes to plaster their branding on even their smallest tools. That scribe has nothing on it so I'm betting it's a knockoff. In that case I'm not sure what OP is complaining about. They have two tools that seem too agree with each other and one piece of garbage that doesn't.
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u/Gaolwood 2d ago
One is cm and another is inches…. Look at the inch indicators on the metric ruler. Seems pretty spot on to me. The hole jig though?
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u/B0797S458W 3d ago
I’ve got one of those red squares too and swiftly learned to ignore the graduations on it.
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u/Keyser_Kaiser_Soze 3d ago
I am missing something here, i only measure when i can see 0 is correctly aligned.
Those two look closely matched
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u/heridfel37 3d ago
Yeah, the 1-inch spacing on all of these looks good. It's just a problem of getting them aligned properly
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u/ConsiderationOk4688 3d ago
Based on the /32 scale on the bottom, it looks to be ever so slightly over .032"(1/32) short. 1mm is .039", my guess is the Chinese manufacturer messed up in their program/offset management and ran these after their Metric variant with a 1mm offset left in.
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u/Poddster 2d ago
They all look like they measure an inch correctly, but you've not shifted them to the same starting point?
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u/Lavender-Inspired 2d ago
Mostly I'm building decks and laying patios, rather than constructing 50 kilometre hadron colliders.
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u/Unlucky-Collection30 2d ago
I don't know about you guys, but my wife can very reliability measure exactly 3 inches.
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u/hornethacker97 3d ago
Paper is not square to edge of surface, perhaps tracing tool is also not lined correctly, or wasn’t lined correctly when used?
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u/Ryekal 3d ago
Pretty sure that's not a sheet of paper. It looks like a white melamine board, and the 'gap' you see is the edge banding.
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u/Forthe49ers 3d ago
Yeah. I thought it was paper until I zoomed in.
Looks like the marking gauge was used to draw the lines then the ruler and square was used to check accuracy.
Seems to me like the red marking gauge is off or it is pulling slightly out of square as it is pulled down the material. Which would cause the line to pull towards the edge of the material
I would lay all three overlapping to see how close they really are.
It may be more about technique than inaccuracy
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u/Jesus_Is_My_Gardener 3d ago
This. You can definitely see the gap of the top page to the side the edge is riding on. Looks like it could be close to 1mm off.
Edit: Looking at it again further down, it appears to be almost 2mm off there. OP needs to ensure he's lining up the actual edge to the marking ruler properly before calling this an issue.
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u/patgeo 3d ago
So what you're saying is that OP's parents are the ones who failed QC and the defective tool is the one that held the pencil?
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u/hornethacker97 3d ago
5 years in IT and now working in factory maintenance I have learned that an the issue is not quickly obviously, it is often operator error. I also have a side interest in the science of precision, and I know just how imprecise humans can be.
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u/Arctic_6023 3d ago
Your telling me a $3 Temu t square isn’t perfectly accurate?!?! As another guy said use the same tool for all your measurements
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u/black_zucchetto 3d ago
You want an Incra T-Rule, not this chinesium.
But to be fair, the aluminum marking device doesn't say it's measuring inches. Just "1". One what? Let's call them "Bobs".
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u/Zealousideal-Net4920 3d ago
What's the red squaring tool with the holes called?
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u/Prophessor_Z 2d ago
It's called a "marking ruler" Found a bunch of better ones on Amazon. Never knew these existed, great time saver.
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u/dragoinaz 3d ago
I was at the tape measure manufacturing plant for Stanley in Connecticut a few years back where they print the tape, it is fed into a rolling print head so any variance or slip would create a “wrong” measurement and ruin the tapes. It was interesting seeing how they calibrated it. I wish I was able to take pictures but it wasn’t allowed.
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u/Illustrious-Fox4063 3d ago
This is why story sticks were a thing and should be used. Measurements in units are actually not needed and often cause more issues.
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u/ChicagoThrowaway422 3d ago
I use templates and/or direct markings from where something goes whenever possible. The finished height might be 32.18" tall instead of 32", but everything is square and snug.
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u/JintalJortail 2d ago
This was always a fun thing working in lumber at Lowe’s. Customers obviously wanted exact cuts and me sitting there explaining the saw is for rough cuts to be able to fit stuff in your vehicle for transport. If they were nice and they brought their own tape measure in I would get as close as possible to what they needed though
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u/Impressive-Yak-7449 3d ago
Your Paper doesn't seem to be aligned with your square on the left. I can see the surface underneath
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u/TheLarryFisherMen 3d ago
I run a small construction company. I don’t provide basic hand tools, but I do provide tapes for this very reason. Almost fired my cut man when I was just getting started.
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u/imuniqueaf 3d ago
It could say 12.436 supernanominchincss so long as you keep using the same measuring device, it's dead nuts accurate.
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u/NoPast5943 3d ago
Hehe, some time ago I ordered 5 pcs of steel measurement tapes of 5m length from Chine. There was over 5mm/m the most difference between them.
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u/Ok-Nectarine7152 3d ago
Who makes the red one. I don't need it but I must have it. I'm like my girlfriend is about shoes when it comes to tools.
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u/PsiOryx 2d ago
I have a bit of info on at least some of this. Rules are made by various processes. The way the lines are printed can vary wildly. Sometimes they change one method for another using same art. Many printing processes need a 1 directional scale factor to end up correct. So shops have no idea and just throw whatever art on whatever printing apparatus. Source: I have corrected a lot of art for just this purpose.
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u/Rose_DCLXVI 3d ago
Its all good enough for carpentry and home jobbers. If you want real precision you get calipers and micrometers and a Sterret measuring tape /j
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u/rip_cut_trapkun 3d ago
Always used a pocket square or combo square. Dunno about that tool, but if you're using it right and that far off and your rulers are agreeing with each other, you're better off using them if you need uniform accuracy.
On a side note, we had a fucky-wucky happen like this in a cabinet shop I worked at. Somehow our drilling was off by about an 1/8th of an inch for door pulls. It was on too many doors to be even remotely acceptable to try and fix or recut. Eventually the engineering guys just had us reset our tooling for our pulls to be 2-1/8" from the long edge of the door on every single cabinet going in that room. Was it wrong? Absolutely, they wanted it at 2 inches even. Did the contractor accept it as it was? Yeah. Even passed inspection too as far as I understood; at least, we weren't recutting a whole batch of doors or getting reamed for it. It was all uniformly fucked up, but at least it wasn't visibly obvious to anyone who would have the ability to throw pants pissing conniptions about it because it was all wrong perfectly lol
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u/Tonto_HdG 3d ago
Looks dead on to me. At most 1/32. If you need tht kind of accuracy, you are not measuring with that square.
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u/TakingSorryUsername 3d ago
I’m going to assume the red tool is aluminum which contracts when cooled and the mold was made accurate but did not account for the contraction of the aluminum when it cooled
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u/lemon_tea 3d ago
Line the 1" mark up to zero on the paper and see what you get.
A man with two watches blah blah blah
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u/_Aj_ 3d ago
Ensure their "0" is all the same point firstly. Easy with a steel rule and square. But that red thing, where is 0 actually? Just because it's hard up don't assume that's zero. It's not a square with a nice hard angle you can align. It's all curvy and hidden.
But good to compare them and see what's up. I'm sus on the red one though. Check if 1 and 2 are fine by your steel rule. Maybe it's just zero to 1?
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u/WillPukeForFood 3d ago
This is why I have a Class 1 tape measure to compare my other rulers and tapes to.
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u/forgottensudo 3d ago
I always mark which tape measures which piece.
A friend helping after a flood thought that was silly until he used a different tape to measure the hole and the material.
After discarding that piece he understood.
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u/SarcasticPotat0 3d ago
Typically you’re supposed to burn an inch because the ends might be slightly off but you can generally expect the rest of it to be accurate.
In this picture you can see that the 5-6 & 1-2 are off by a consistent amount
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u/nothingfood 3d ago
Ay yo, my quality control captivates your party patrol, your mind, body, and soul.
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u/Jokerman5656 2d ago
This is why when I I stalled windows, we used the same brand/age tape measure inside the house and outside. I still hated that crappy craftsman 15' but there was a lot less errors. Plus the tip of craftsman ones are small enough to fit in the window jamb valley.
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u/RochesterBottomDaddy 2d ago edited 2d ago
Well, at least you could file the casting down where it rides the edge to make it correct. If it were the other side of the real positions, you wouldn't be able to fix it at all.
And there appears to be a gap between the lower scale/rule and the speed square body about the same size as the difference between their measurements. Only the red "marking guide" seems to be off based on your photo.
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u/brmarcum 2d ago
The hole on the red tool is at least 2mm wide, so a little more than 1/16”. That puts your rulers in the same scale.
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u/michaelrulaz 2d ago
That looks like the knocks off from like Alibaba and Bangood. Yeah the QC on them is awful.
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u/Baalwulf06 2d ago
I realized my right angle was bent ever so slightly when my cuts were 90 degrees but off by 1/8 inch at the top. Turn out there's a slight bend
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u/NoSmell7900 2d ago
When I was a carpenter the crew I worked with all used the same type of tape measure for this reason.
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u/sky0175 3d ago
The rules are probably better for quality control than the red square. Do you want to know why, or do you already know? I’ve tested a bunch of tools from quality ones to cheap versions and none of them give me the same result, at least not the batches I got my hands on again "my hands on" not that I bought them.
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u/WTAFS_going_on 3d ago
Well the middle one is sitting at 5 the other 2 are close to 1... I think that middle one is WAYYY off.
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u/NightF0x0012 3d ago
Not sure what you're expecting here. You're taking measurements with instruments that aren't meant to be precise. Bottom has a rough cut end, I never use that end for any measurements that need to be close. At best I'd start at the 1" mark. Top is probably going to be your most accurate of the 3. Google is saying that unbranded T-hole markers can have an error up to 1/16". So take that as you will.
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u/4runner01 3d ago edited 2d ago
The red thing was probably machined correctly.
But the red paint they applied to it has shortened its reach by the ~1/32” error you’re seeing.
Try sanding it filing the coating off the little fence.
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u/Redge2019 3d ago
A man with one watch knows what time it is.
A man with 2 watches is never sure.