Can someone help me generate a standard mic thread (5/8" x 27)

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onekk
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Re: Can someone help me generate a standard mic thread (5/8" x 27)

Post by onekk »

Main problem is that with diy 3d printing internal holes are not printed with enoug precision to be useful as threads, that usually require some precise dimensioning.

better to make a hole and use a tap to make a real thread on it.

Many 3d printed projects use some inserts and similar workaround to employ precise threaded insert most easy is to heat and press fit a standard threaded insert or a nut in the printed part.

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Carlo D.
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drmacro
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Re: Can someone help me generate a standard mic thread (5/8" x 27)

Post by drmacro »

Krypto wrote: Tue Mar 21, 2023 2:20 am
drmacro wrote: Tue Mar 21, 2023 12:18 am Unfortunately it does not offer 5/8 x 27 since it is, indeed, not a thread defined by a standards organization...
The great thing about standards is that there are so many of them.

Believe it or not, 5/8" x 27 TPI is a standard microphone thread. Seems to still be used in Europe too.

https://www.musicalhow.com/microphone-s ... ead-sizes/

It's not going to help you with the Freecad hole tool, however.
The "mic thread" has been the standard of the performing industry for decades, at least since the 1940's. But, I don't think it is included in international thread standards like DIN, ISO, etc. It can be found under UNS (Unified Special) in most listings. A UNS designation is any thread that does not fall under UNC, UNF UNEF etc.
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papyblaise
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Re: Can someone help me generate a standard mic thread (5/8" x 27)

Post by papyblaise »

if I calculate correctly, this gives Dia 15.5 x 0.95 mm or almost M16
know the characteristics of the net '(55° or 60° angle) and draw it manually with a little clearance
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papyblaise
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Re: Can someone help me generate a standard mic thread (5/8" x 27)

Post by papyblaise »

if I remember correctly 5/8 is the hole drilling dia (unlike ISO)
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Krypto
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Re: Can someone help me generate a standard mic thread (5/8" x 27)

Post by Krypto »

drmacro wrote: Tue Mar 21, 2023 10:26 am The "mic thread" has been the standard of the performing industry for decades, at least since the 1940's. But, I don't think it is included in international thread standards like DIN, ISO, etc. It can be found under UNS (Unified Special) in most listings. A UNS designation is any thread that does not fall under UNC, UNF UNEF etc.
It's not a fastener spec as it originated from USA gas light fittings which are all 27 TPI (non-tapered) and you still see the thread used today with some light and electrical fittings and of course MIC stands. I think Coleman still uses it with some parts of their gas lanterns. Since gas lights aren't much of a thing nowadays I'm not sure if the specs are still printed, but I think an old Machinery's Handbook I have in the shop from the 40's has it listed.
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Re: Can someone help me generate a standard mic thread (5/8" x 27)

Post by drmacro »

Krypto wrote: Tue Mar 21, 2023 12:59 pm
drmacro wrote: Tue Mar 21, 2023 10:26 am The "mic thread" has been the standard of the performing industry for decades, at least since the 1940's. But, I don't think it is included in international thread standards like DIN, ISO, etc. It can be found under UNS (Unified Special) in most listings. A UNS designation is any thread that does not fall under UNC, UNF UNEF etc.
It's not a fastener spec as it originated from USA gas light fittings which are all 27 TPI (non-tapered) and you still see the thread used today with some light and electrical fittings and of course MIC stands. I think Coleman still uses it with some parts of their gas lanterns. Since gas lights aren't much of a thing nowadays I'm not sure if the specs are still printed, but I think an old Machinery's Handbook I have in the shop from the 40's has it listed.
As noted if you look at listings of the UNC, UNF UNEF, and UNS designations it is listed.

The first paragraph from the Wikipedia:
"The Unified Thread Standard (UTS) defines a standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada. It is the main standard for bolts, nuts, and a wide variety of other threaded fasteners used in these countries. It has the same 60° profile as the ISO metric screw thread, but the characteristic dimensions of each UTS thread (outer diameter and pitch) were chosen as an inch fraction rather than a millimeter value. The UTS is currently controlled by ASME/ANSI in the United States. "

The rest of the article goes on to discuss similar to your notes above. Especially the link to Origins.
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DewRagDave
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Re: Can someone help me generate a standard mic thread (5/8" x 27)

Post by DewRagDave »

I too was looking for a way to generate a TPI other than the "20" that Fasteners Workbench seems to default to. Here is how I did it. Start by dividing 1000 by 27 getting 37.0370370. Open up the Inch Tap in Fasteners. In diameter enter Custom. In diameter custom enter .625". In length enter your thickness (I put in .25" for the thickness of the PAD). In pitch Custom enter the "37.03703 thou" from the calculation above. Then enter true for thread. I 3d printed this with the thread size I needed and was able to screw my bolt right in. I wish that they included a TPI setting but it's free, so... You will note that FreeCad automatically creates a Screw Tap label of "15.875 x 6.35" which must be the metric equivalent of "5/8-27" (I guess?) Hope that helps. SEE PIC!
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TheMarkster
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Re: Can someone help me generate a standard mic thread (5/8" x 27)

Post by TheMarkster »

1) Install ThreadProfile workbench from Tools -> Addon manager -> workbenches
2) Open Shalmeneser's file.
3) Delete Hole object (but leave Sketch005)
4) Double click Body to make it active
5) Go to ThreadProfile workbench
6) Create new VThreadProfile object
7) select 5/8" - 18 UNF from the Presets property
8) Change pitch to =25.4/27 (assumes you are in millimeters, else use 1/27 if in inches)
9) Set Height property to 16 mm
10) Select VThreadProfile object, attach it to Sketch005.Edge1, concentric mode (the circle in that sketch)
11) With VThreadProfile object selected create the Helix object from the ThreadProfile workbench
12) Set Internal or External property to Internal
13) Select VThreadProfile and Helix, click the sweep toolbar icon in the ThreadProfile workbench, click OK in subtractive pipe dialog

Note: Model fails check geometry bop check in 0.21, but passes if done in 0.19. There could be some regression in OCCT. If I create it in 0.19, and then open in 0.21 it passes the test, but upon recompute it then fails the test.

Alternatively, you can make a subtractive helix beginning at step 11 and reference Base-Z as the axis, Pitch = VThreadProfile.Pitch, Length = VThreadProfile.Height = 16.

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