KY-040 rotary encoders: what's the thread size ?  - Page 1
Forum section: electronics / projects

author: GrandTheftAuto4life
author_rank: Contributor
timestamp: September 23, 2020, 03:15:51 pm
content: Hello. I am trying to identify the thread on these KY-040 rotary encoders I have.I have tried these nuts:M6: too smallM8: way too big.UNF:1/4"–285/16"–243/8"–24None of them seem to fit the KY-040 threaded shaft, so what could it be?

author: Buriedcode
author_rank: Super Contributor
timestamp: September 23, 2020, 04:38:43 pm
content: Quote from: GrandTheftAuto4life on September 23, 2020, 03:15:51 pmM7?

author: Cerebus
author_rank: Super Contributor
timestamp: September 23, 2020, 05:38:10 pm
content: They look to me to be mechanically identical to the ALPS EC-11. The shaft/nut on that is M7x0.75.

author: GrandTheftAuto4life
author_rank: Contributor
timestamp: September 23, 2020, 05:38:42 pm
content: I've located a new battery so i could try to measure it, but i don't know what the correct way is so:

author: mathsquid
author_rank: Frequent Contributor
timestamp: September 23, 2020, 09:05:45 pm
content: Quote from: GrandTheftAuto4life on September 23, 2020, 05:38:42 pmThis page might be helpful:http://theoreticalmachinist.com/Threads_UnifiedImperial.aspx

author: sleemanj
author_rank: Super Contributor
timestamp: September 23, 2020, 09:23:46 pm
content: As above it will almost certainly be M7 (fine), that is the common size for encoders and pots for some reason.

author: GrandTheftAuto4life
author_rank: Contributor
timestamp: September 24, 2020, 07:42:19 am
content: Quote from: mathsquid on September 23, 2020, 09:05:45 pmIt looks neat but i just noticed that M7 is missing in the metric versionQuote from: sleemanj on September 23, 2020, 09:23:46 pmperfect. now the only issue is getting hold of them. Seems like i have to buy them from germany as I can't find anyone selling them in sweden

author: Cerebus
author_rank: Super Contributor
timestamp: September 24, 2020, 01:46:59 pm
content: Quote from: GrandTheftAuto4life on September 24, 2020, 07:42:19 amM7 isn't apreferredmetric size, but is realisable using a 7mm base measurement and the standard metric thread construction method (It actually falls into the '2nd choice' column in the full pukka ISO tables, American references are usually to ANSI B1.18M-1982 not to ISO 262. The 7mm sizeismissing in the ANSI standard.). Note that we're talking about afinepitch (0.75mm), not coarse (1.00mm). If you specify M7 without specifying the pitch you'll almost certainly land up with a coarse pitch thread.

author: TimFox
author_rank: Super Contributor
timestamp: September 24, 2020, 02:25:00 pm
content: If it were an inch thread, normal American potentiometer and similar bushings are 1/4-32 UNEF (extra-fine) or 3/8-32 UNEF.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 25, 2020, 08:46:35 am
content: For measuring the pitch of the thread:Hold a ruler next to the thread, and then make a macro photograph of both the tread and the ruler, and reconstruct on your PC by using some measurement software, or a simple screen ruler.M7 is an existing thread, although not much used in engineering.For fine pitch, beware that there can be different sizes of fine pitch for the same outer thread diameter. So check before ordering.Alternative:Just glue the thing in place.

author: Nominal Animal
author_rank: Super Contributor
timestamp: September 25, 2020, 10:05:02 am
content: A couple of years ago, I got a M7x0.75 tap set (taper tap and a plug tap), as I wanted to tap the holes for a couple of potentiometers in a cast-aluminium enclosure. I found that better than making a larger hole and using a thin nut. (You can find those nuts for really cheap on eBay and Amazon, though.) I did still use the thin nuts, but this way they are just for locking, not for holding.There are three M7 thread pitches: 0.5mm, 0.75mm, and 1.0mm. 1.0mm is the common, coarse one. 0.75mm is the fine one, used in potentiometers, rotary encoders, and some connectors. I don't know where M7x0.5 is used, but I have seen both taps and dies for it; I do believe it is called "superfine". A complete metric tap and die kit should have both M7x1.0 (in the "coarse" subset) and M7x0.75 (in the "fine" subset) taps and dies.(M7 hex nuts and bolts also use a 11mm spanner, which is the first one you lose when you get a full set. Don't ask me why, I think the toolshed gnomes take them.)For tapping a M7x0.75, technically you need a 6.2mm (6.188mm) diameter hole first.Some M7 taps have a sharp enough cutting edge that they can cut the extra 0.2mm away if you are careful (and use cutting oil on thin harder materials like stainless steel), so you can start with a 6mm hole, then use the taper tap, and finish with the plug tap. Mine works fine in aluminium (i.e., I can use 6mm HSS drill bit and the end result is exactly the same as using 6.1mm drill bit, because the tap enlarges the hole) and 1-2mm thick steel. I wouldn't try it on thicker steel parts, though.On thicker harder materials (stainless steel etc.), you should use a 6.1mm or 6.3mm drill bit, or 6mm drill then an expandable reamer or a DIY flapper (dowel or wooden rod, say 5mm in diameter, slotted, with a piece of sand paper through, so that when you rotate it in a drill, it "sands" the hole larger). Otherwise you can break the tap, which is no fun at all.

author: Cerebus
author_rank: Super Contributor
timestamp: September 25, 2020, 01:18:50 pm
content: Quote from: Nominal Animal on September 25, 2020, 10:05:02 amThey run off and form troilistic marriages with lost biros and lost single socks.

author: Cerebus
author_rank: Super Contributor
timestamp: September 25, 2020, 01:47:11 pm
content: Quote from: Doctorandus_P on September 25, 2020, 08:46:35 amOr you could measure them with an actual proper measuring tool, vis a £4 set of thread gauges and get an accurate answer in a few seconds rather than pixel approximations in ten or twenty minutes and still be left guessing if you've picked the right thread size. The pitch difference between 0.75 mm metric and 32 tpi is 43 microns per 'tooth', good luck determiningthatfrom a photograph of a thread perhaps 3-5 individual threads long. However, using a cheap thread gauge it's obvious whether you've got the right thread or not. Sometimes "use a computer" is very muchnotthe right answer.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 29, 2020, 01:21:49 pm
content: I think you underestimate the quality of average photo camera's these day's.With 5 tooth, 4 threads the difference in this case would be 0.172mm and this can easily be several pixels.sure, thread gauges are useful, especially if you use them more often, but they're pretty limitited to only measuring thread pitch, while with a simple ruler, standard camera and PC you can do all kinds of different measurements.Thread gauge also probably has to be bought, which implies shipping time, while just taking a quick photograph and measuring it on your own PC is a few minutes.But whatever you think of it. It is a valid way of measuring small things fairly accurate and therefore worth mentioning.