I have different packs of screws. They all have unique codes. E.g. 6-35-B1120-4RE*12

  • 6 might be the diameter # (which is approx. 9/64 inches).

  • 35 might be the # of threads. (It doesn't appear to have that many, but it's so small. Perhaps I can't see it, or perhaps threads aren't counted the way I'm first inclined to think they are.)

  • 1120 might be 11/20 inches long.

  • R might stand for replacement (they came as additional supplies with a laptop).

Is any of this correct? Either way, that still leaves:

  • B: Bottom? Referring to the shaft length?

  • E: I have no guesses.

  • 4, *12: If R does stand for replacement, the pack came with neither 4, nor 12 screws. It came with 5. There's the possibility that I just wasn't given the original quality from the seller. I have no other guesses what those numbers might stand for.

If it helps, I have 2 other packs of screws, each containing a different string of characters containing R:

  • 8R0*1

  • 4R2*4

Screws in labelled plastic bags

  • Where are you on this planet? Commented Feb 25, 2018 at 4:09
  • USA. I added a pic too: dropbox.com/s/2t7f6qfispke8m7/screws.jpg?dl=0
    – abcjme
    Commented Feb 25, 2018 at 4:22
  • those look like part numbers from some equipment manufacturer ... what are the screws from? .... why are you asking?
    – jsotola
    Commented Feb 25, 2018 at 5:39
  • @jsotola 2 different laptops actually. A couple packs are from an msi XOTICPC laptop. 1 pack is from an OriginPC EON17-SLX laptop.
    – abcjme
    Commented Feb 25, 2018 at 5:43
  • Must be a metric thing because standard screw sizes for #6 are 6-24 and 6-32 the 24 & 32 are the threads per inch. For #4 screws 4-40 is the most common standard size, #8 there are 24 & 32 threads per inch when the sizes get into the 1/4" range the thread pitch drops to 20. I have never seen a screw size expressed as in your example.
    – Ed Beal
    Commented Feb 26, 2018 at 15:17

3 Answers 3


Okay, I read this article, https://en.wikipedia.org/wiki/Part_number , and I did a bunch of measurements and comparisons.

I might not be able to figure it out with 100% confidence, but I feel satisfied with my understanding now.

  • The 6-35 is redundant. A 6 Gauge screw is one that has a head diameter of 3.5 mm.
    • EDIT: Actually, the 35 probably isn't redundant. It's probably referring to the pitch (the distance between each thread)! Thus, the 35 would refer to a 0.35 mm pitch.
  • Some Googling suggests that you're right, @Jeff Cates , about the B: it's the strength/type of the compound.

  • The 20 is the diameter of the shaft (2.0 mm).

  • The 4 is the length of the shaft/screw in mm (whether or not length includes the head depends on the head type).

  • The R stands for Replacement.

  • The *12 is quantity (the company for the screws and the company for the laptops are different, so it's quite likely that the laptop company removes some of the original quantity).

That just leaves the 11 and the E. Considering that B is the compound, I'm inclined to think that 11 is the shaft and/or head model/style. Considering that all packs have a "1" (11, 21, AND 61), and they're all Cross-head, the "1" might refer to a Cross style. As for the E, it might be some sort of personalized/trivial note about the part (e.g. version #).

As for the question about my motive, @jsotola & @Jeff Cates: if I'm going to be working with something, I like to understand deeply how it works. Also, this can help me organize my tools better.

  • Please accept your answer to close the question.
    – isherwood
    Commented Feb 25, 2018 at 16:07
  • @isherwood The system won't allow me to.
    – abcjme
    Commented Feb 26, 2018 at 19:19
  • Hmm. Maybe you need more reputation.
    – isherwood
    Commented Feb 26, 2018 at 19:21

Oh dear, this is a case of looking at noise and trying to find signal. Generally, part numbers are based on "a part number is 4635 because the last part they ordered was 4634". Sometimes they have revision codes or vendor codes. But part numbers are chosen to be convenient to the manufacturer, not to make any sense to outsiders.

If you want to hunt signal, you need to first stop and understand what signal you are hunting -- which means you need to learn the tradecraft of the industry you are studying. Grasping at straws with wild guesses like #6 and metric thread pitch (which would never happen) is a complete and total waste of your time: it is avoiding knowledge rather than seeking it.

First, fasteners are standardized to only a few diameter/pitch match-ups: 10-24 and 10-32, but never 10-30. And they pick a system, Imperial or Metric, and they go all in.

So your first step is to stop guessing and determine what the screw actually is, and use that as a starting point.

This is a laptop, so Metric. Get a chart of standard metric threads (diameter/pitch pairs), and either millimeter graph paper or a calipers.

  • You're looking for round diameter sizes like 3mm, 3.5mm, whatever.
  • Then take a hi-res camera picture from a distance watch your parallax and count some threads. In the metric system, the figure is millimeters between threads, e.g. 0.35 pitch = each thread is 0.35mm apart, or 20 threads in 7mm. In Imperial, it inverts to threads per inch.
  • Make sure the diameter and thread pitch match up to a standard pair. If it doesn't, your data is wrong! Remeasure or switch systems.
  • Now measure the length. You know you're in the right system (Imperial/metric) when the screw length snaps to a nice, even number like 15mm or 3/4". Learn how to measure lengths on button-head vs countersink screws, they work differently.

Now you have screw length, diameter and thread pitch, in hard numbers. Now you can compare those to numerals in the part number. See how much easier that is?

I doubt you will see anything. I have a feeling that company starts every part number with 6-36, and that may be assigned to them by their Chinese factory. I expect the tail numbers are vendor codes or revision numbers. Leaving only about 8 digits for the part number proper, for all parts from that company. There just isn't room there for encoding data about screws in plaintext.


Laptop screws are generally metric. I would assume that if the numbers have any meaning it would be in mm. 6 being the diameter, 1120 being the length. Look at the different screws you have and the numbers on them and compare each screw. All a 6 and same diameter? Longer screws with larger thousands numbers, length! All have a similar thread pitch? Could be the 35. And *# probably means quantity originally shipped in the package. The B in the code could be the thread locking compound, which is the strength of the compound. Usually blue is the lowest, making it the easiest to remove later, yet still have a locking grip, and the screws all having blue on the ends. Some screws that need more locking power would have red on the ends. As far as other numbers I am not sure, but could be an indicator of the screw strength.

One way to figure the numbers out, would be if you measure them.

As posted in a comment, why are you asking?

  • None of those guesses are standard or likely sizes for PC screws. 6mm is analogous to 1/4". Like Imperial, there are certain thread pitches semi-standardized for each screw size, in metric the thread pitch is the spacing, not the pitch. Commented Feb 25, 2018 at 7:30
  • Just guesses, but yes, it most likely is just a common part number. But I would guess that the numbers corrolate to the size in some way.
    – Jeff Cates
    Commented Feb 25, 2018 at 23:01
  • Looks as though I was pretty close in determining the approximate guess to what the numbers meant. I just always kept mine in sorted bins, and when something called for a screw, I would use what was called for and not wonder what the numbers meant.
    – Jeff Cates
    Commented Feb 25, 2018 at 23:05

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