Fan screw diameter and thread pitch?

[Guest]

You would think this would be an easily answered question, but I can't find the answer anywhere!

Apparently I have two different fan screws with two different thread pitches.

I know one is 5mm diameter, with a T16 pitch. The other is 4.9mm with a T14 pitch.

What does T16 and T14 actually mean? And which one is "standard"?

[W-L]

17 minutes ago, jonnyGURU said:

You would think this would be an easily answered question, but I can't find the answer anywhere!
Apparently I have two different fan screws with two different thread pitches.
I know one is 5mm diameter, with a T16 pitch. The other is 4.9mm with a T14 pitch.
What does T16 and T14 actually mean? And which one is "standard"?

It would depend on the thread type if it's a metric machine screw M5 would have a thread pitch of 0.8 thread per mm. 

 

Not heard of a T based thread unless it's trapezoidal or is this the self tapping variety?

[Guest]

1 minute ago, W-L said:

It would depend on the thread type if it's a metric machine screw M5 would have a thread pitch of 0.8 thread per mm. 

 

Not heard of a T based thread unless it's trapezoidal or is this the self tapping variety?

It's a fan screw.  They're self tapping. 

 

 

[BobVonBob]

As far as I know T14 and T16 would describe trapezoidal screws, the sort of screws you'd see as a 3D printer axis, with an outer diameter of 14 and 16mm respectively.

 

Are they self tapping screws? That's the only kind of screw I can think of that would be that wide in a computer. If so neither is really standard, they cut the threads in the plastic fan casing as they get installed. I suspect manufacturers will just go with whatever screw has the right outer diameter to fit in case holes and is cheapest.

Edited July 4, 2020 by BobVonBob
Just answered that.

[W-L]

5 minutes ago, jonnyGURU said:

It's a fan screw.  They're self tapping. 

Hmm I'm not very familiar with self tapping thread but I'm not sure is there is a strict standard for fan screws since I have seen the pitch of fan screw vary between manufacture's

 

Looking at this manufacture's spec I can see they used a metric value for their fasteners with a 1.4 threads per mm which gives us an approx of 18 threads per inch.

https://media.digikey.com/pdf/Data Sheets/Mechatronics PDFs/CS-1_Dwg.pdf

 

However on this metric self tapping chart the fastener would fall in as a ST4.8 with a pitch of 1.6 threads per mm.

https://amesweb.info/Screws/Self-Tapping-Screw-Sizes-Metric.aspx

[Guest]

I wonder if T16 means 16 threads per CM as opposed to 1.6 threads per MM.

 

I'll try to get better looking drawings later, but here's the two that I got from the two vendors:

 

 

 

[W-L]

30 minutes ago, jonnyGURU said:

I wonder if T16 means 16 threads per CM as opposed to 1.6 threads per MM.

 

I'll try to get better looking drawings later, but here's the two that I got from the two vendors:

Usually threads are done via pitch in relation to inch or threads per mm, however that would make sense if it's based on threads per CM. With 16 threads per CM it would be the same as 1.6 threads per mm and be nice and coarse. Never heard of it being referenced as threads per CM however but seems logically correct in this case. 

 

16 Threads per CM / 10MM in a CM = 1.6 Threads per MM.

[Guest]

1 hour ago, W-L said:

Usually threads are done via pitch in relation to inch or threads per mm, however that would make sense if it's based on threads per CM. With 16 threads per CM it would be the same as 1.6 threads per mm and be nice and coarse. Never heard of it being referenced as threads per CM however but seems logically correct in this case. 

 

16 Threads per CM / 10MM in a CM = 1.6 Threads per MM.

Maybe they do threads per CM because the threads are so course (because they're tapping).

 

But I still don't know what is "standard" for a case fan.  LOL!

 

[W-L]

9 hours ago, jonnyGURU said:

Maybe they do threads per CM because the threads are so course (because they're tapping).

 

But I still don't know what is "standard" for a case fan.  LOL!

1.4 to 1.6 seems like the common choices. If I were to choose personally I'd probably recommend the coarser thread myself, since you have less material to displace and with the higher helical angle less turns to put in the screw. If there is the option to have the type with the notched end that also is beneficial in cutting a thread instead of just forcing material out of the way. 

 

I've used startech ones before and they are probably the coarsest thread form with T12.

https://sgcdn.startech.com/005329/media/sets/12FANSCREW_Manual/12FANSCREW.pdf

[Guest]

Well.. You won't believe what I found out.

 

T## is actually THREADS PER INCH!!  Imagine that!  A metric screw using threads per inch.

 

So I think I found my problem.  Since the "T14" has fewer threads, it's not staying tight in a fan with a thinner frame.  EVEN THOUGH the courser thread is actually slightly larger diameter (.1mm).

 

[TheProfosist]

I know im resurrecting this thread but it's the only one that seems to have gotten close to what these screws actually are.

 

Did anyone find them on McMaster or the like?

 

 

I'm specifically looking to buy bulk 12mm ones as I prefer that length and would like to avoid ~$0.30 a screw

 

https://www.performance-pcs.com/diy/fan-screws-metal/extended-fan-screw-12mm-long-black-scr-04a.html

 

 

Quite surprised to see @jonnyGURU as an active member!