Cheap Ruler accuracy

Discussion in 'Luthier's Corner' started by TurdFergusons, Mar 17, 2023.

  1. TurdFergusons


    Mar 15, 2023
    Hey I have a cheap harbor freight metal 40 inch ruler that I got for 5 dollars that have mm markings on it and I was wondering if it would be accurate enough for marking out frets.
    It looked a little suspicious when comparing it to another 12 inch metal ruler that I have so I don’t know.
  2. ddnidd1

    ddnidd1 Supporting Member

    Maybe I'm missing something, but either the markings on the two rulers match up exactly or there is a problem with one of the rulers.
  3. TurdFergusons


    Mar 15, 2023
    Very slightly off over a 12 inch length like Maybe less than half a mm at the end of the ruler
  4. tlc1976


    Aug 2, 2016
    Do you have a good metal tape measure to compare them with? Just start at the 1 inch mark, don’t trust the end hook.
  5. ddnidd1

    ddnidd1 Supporting Member

    It appears the ruler you purchased goes for $4.99. For such a critical project do you really want to rely on this ruler since it already looks like it's off.
    Patrice B, groooooove, MCF and 4 others like this.
  6. ardgedee


    May 13, 2018
    Generate the fret spacing you need in FretFind2d, print it out, and use that. Then you don't have to worry about the quality of the ruler markings.
    BishopJP, Grinderman, MVE and 8 others like this.
  7. Beej


    Feb 10, 2007
    Vancouver Island
    Quoted for emphasis. :thumbsup:
  8. MIMike


    Jan 1, 2013
    West MI
    Just make sure not to do any “scaling” on the printer output…
    Engle, zenrad, groooooove and 2 others like this.
  9. BuddhaFingas


    Aug 16, 2019
    Ive never laid out a fretboard before, but I would assume you need better than 1mm precision for that job anyway?
    Quarter-millimeter at least? Hundredth-inch?
  10. If you look at fretfind2d or the StewMac fretboard calculator they’re measuring in thousands of an inch and hundreds or thousands of a mm. Fretfind2d is really easier. As mentioned just print out the scale and number of frets you want and use that as a template. You can check the 12th fret measurement to make sure it printed correctly but the program will do multiscale boards and print to the width you want.
    Grinderman and Beej like this.
  11. BobKos


    Apr 13, 2007
    For the OP -cheap rulers and cheap tape measures are terrible if you REALLY need something to be accurate. If you are just transfering a dimension and the actual dimension doesn't matter, they're OK. But if it has to bee a SPECIFIC dimension, then use something good.
  12. swink


    Jan 10, 2019
    The key word in this sentence....
  13. Smith357


    Jul 7, 2018
    Precision measurements require precision tools.
  14. Michael Stanley 2112

    Michael Stanley 2112 Supporting Member

    Aug 23, 2020
    Ding! Ding! Ding! Ding! Ding!
    tlc1976 likes this.
  15. Flying B

    Flying B

    Apr 29, 2018
    I had a cheap combi-square once in mm, and the issue was that there was about 3mm gap from the end of the ruler to the start of the graduations! Not much use.
    The fret printout thing seems like a good idea, but unless you have some kind of industrial sized printer, surely you will end up having to join pieces together? Which kind of feels like inviting more chance of errors.
    Flamingo21 likes this.
  16. coyote1


    Mar 23, 2012
    mikewalker, MCF and tlc1976 like this.
  17. Planespotter


    Oct 11, 2015
    Thank you! I was going to say the exact same thing!
  18. Dirk Diggler

    Dirk Diggler Supporting Member

    Mar 3, 2004
    Anytown USA
    I like to use calipers for my multiscale layouts. Also I do layouts on Blue painters tape attached to the fingerboard.
    I use a scribe to mark, even a pencil mark can throw things off.

    Precision is required, but also any mistakes you make as you go up the neck can be cumulative.
    Good luck,
    Five or Six and Plain Old Barry like this.
  19. Plain Old Barry

    Plain Old Barry Supporting Member

    Mar 1, 2018
    If you're in CT, you're more than welcome to compare it to my shop standard, a Starrett 24" combo square blade.

    I have a bunch of HF metal rules, but I use them was straight edges and for comparisons, so have never bothered to look at the markings. By comparison, I mean jobs with a stop clamped to them to set up fence parallelism, placing marks on the ruler and moving from part to part, stuff like that...

    The interesting thing about HF stuff is we are sometimes the QC inspector. Sometimes we get a winner, sometimes not so much. My opinion of them changed drastically when a local store opened up, as a I could choose the exact example of each item. When I could only order from them by mail I got a lot more clunkers.

    One thing I learned from an HF corporate person is that seemingly identical items with different part numbers may or may not be identical in QC. The different number denotes different factories sourced the item and attempted to make the identical item, but results vary.
    zenrad, mikewalker and ardgedee like this.
  20. FullumMusic

    FullumMusic Commercial User

    Oct 13, 2022
    Queens, NYC
    Audio/Music software developer, contracted with a company you've heard of and deving my own stuff.
    Seems like you already know the ruler isn't accurate. Unless, of course, the other ruler you compared it to is the one that’s off? Only way to know is to compare 5 or 6 rulers and see how accurate they all are compared to each other.

    Or just get an accurate measuring tool from a luthier supply or engineering store and not worry if it’s accurate enough.

    There’s an old adage, “you’re not rich enough to afford cheap tools.” (Maybe you are rich enough but that’s not the point of the adage.) ;)