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Why are standard M54 male threads so short?

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21 replies to this topic

#1 Peter in Reno

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Posted 17 September 2020 - 05:04 PM

It makes it harder to increase or change spacing there.

 

Peter 


Edited by Peter in Reno, 17 September 2020 - 05:08 PM.


#2 Peter in Reno

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Posted 17 September 2020 - 06:18 PM

Here is a sample M54-to-2" nosepiece. I only see two threads!!!!!

 

IMG_1490_Compressed.JPG

 

Peter



#3 Peter in Reno

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Posted 17 September 2020 - 06:52 PM

Maybe, but what about T-Threads? They seem to be at least four threads long. Besides my QHY OAG-M is attached to QHY CFW3 filter wheel and the filters are mile away from colliding with whatever is attaching to OAG.

 

Peter 



#4 andysea

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Posted 17 September 2020 - 06:55 PM

Those are indeed very short threads. I usually prefer at least 5mm of threads, that gives a firm connection. I wouldn't even know how to machine threads that short.


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#5 Peter in Reno

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Posted 17 September 2020 - 07:00 PM

Even Preciseparts.com threads depth is also about two threads long. I wonder if it's because the bigger the diameter the fewer threads necessary for firm connections. But that does not help to add spacers.

 

Peter 



#6 andysea

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Posted 17 September 2020 - 10:49 PM

I honestly don't know. In order to cut threads I need a few mm, probably 4mm is the minimum that I can do....maybe 3.5mm. That is with my lathe. I wonder how they cut threads so tight. They probably use some super fancy CNC machines.



#7 sn2006gy

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Posted 17 September 2020 - 10:52 PM

I honestly don't know. In order to cut threads I need a few mm, probably 4mm is the minimum that I can do....maybe 3.5mm. That is with my lathe. I wonder how they cut threads so tight. They probably use some super fancy CNC machines.

I have to chuckle over here knowing you have some super fancy scopes.. you don't have a super fancy CNC? :D  (me neither and with our tech shop closed i lost access to the ones i did have.. boooooo)


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#8 rockstarbill

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Posted 17 September 2020 - 10:54 PM

I have to chuckle over here knowing you have some super fancy scopes.. you don't have a super fancy CNC? laugh.gif  (me neither and with our tech shop closed i lost access to the ones i did have.. boooooo)

Probably should not be rude to people because they have nice gear. He does have a lathe and is a pretty nice guy. 


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#9 sn2006gy

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Posted 17 September 2020 - 10:58 PM

I know Andy is a super nice guy. (i've chat with him on discord when I was trying to buy an Epsilon and match it to my camera)  My comment was tongue in cheek thus the smiley.

 

I have a crappy harbor freight lathe... no way i can do those short threads either.



#10 bugbit

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Posted 17 September 2020 - 11:02 PM

Read sometime back that 3 threads would deliver full holding power. One of those huh? moments.



#11 andysea

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Posted 17 September 2020 - 11:45 PM

LOL no offense taken :) The inability to cut those tight threads is probably more related to the operator (me). 



#12 Peter in Reno

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Posted 17 September 2020 - 11:48 PM

I'm going to have to search for M54 thread specifications and I suspect it won't be easy to find.

 

Peter



#13 andysea

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Posted 17 September 2020 - 11:55 PM

Peter, all you will find is the different diameters.  I have the machinist's handbook and I can post those parameters if you like. Typically the specifications define the maximum and minimum outer and inner diameter but that's about it. The angle is 60 degrees which i the standard and the other parameter if of course the pitch which for those threads I think is 0.75.

It is actually interesting how much variability there is in threads from different companies. Even with the same thread nominal size there is a variation. I just got into the habit of matching whatever adapter I am making to the actual part that It needs to thread into. Rather than just going with the specs.



#14 Peter in Reno

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Posted 18 September 2020 - 12:02 AM

Well, I was referring to specifically for this hobby. Even Agena Astro sell M54 spacers and their threads are also 2 to 3 threads long.

 

https://agenaastro.c...acer-set-3.html

 

This T-Thread spacer seems to have 4 threads long:

 

https://agenaastro.c...apter-t-16.html

 

Peter


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#15 Peter in Reno

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Posted 18 September 2020 - 12:23 AM

Maybe I could contact Precise Parts and ask them about the reason about M54 specifications for this hobby.

 

Peter



#16 rockstarbill

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Posted 18 September 2020 - 12:49 AM

If you want longer threads just use the option for a generic M54 adapter. 


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#17 Peter in Reno

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Posted 18 September 2020 - 01:51 PM

Here is Precise Parts response and I agree with him:

 

"All our custom adapters threads are made to match the devices they are intended for. M54 is no exception. If a male thread on a PreciseParts connector seems short it is because it has to fit a shallow female on the device it is designed for.

 

There is no such thing as a standard-length thread in the astronomy equipment market."

 

Peter


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#18 telfish

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Posted 18 September 2020 - 05:53 PM

I  bought a set of these m54 extensions. Nice quality more than enough thread length.

 

https://www.aliexpre....595c4c4dziNA8o



#19 deepanshu29

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Posted 21 September 2020 - 11:55 AM

Here is Precise Parts response and I agree with him:

 

"All our custom adapters threads are made to match the devices they are intended for. M54 is no exception. If a male thread on a PreciseParts connector seems short it is because it has to fit a shallow female on the device it is designed for.

 

There is no such thing as a standard-length thread in the astronomy equipment market."

 

Peter

I asked PreciseParts to adjust the length for an adapter I wanted on the camera side connection. The adapter was intended for QHY367C with M54 and FSQ106 M54. PreciseParts refuse to do so and said their thread length are decided based on manufacturer's recommendations. I measured the female thread depth in QHY367c and it has little over 8mm thread available.  ¯\_(ツ)_/¯


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#20 Peter in Reno

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Posted 21 September 2020 - 12:03 PM

I asked PreciseParts to adjust the length for an adapter I wanted on the camera side connection. The adapter was intended for QHY367C with M54 and FSQ106 M54. PreciseParts refuse to do so and said their thread length are decided based on manufacturer's recommendations. I measured the female thread depth in QHY367c and it has little over 8mm thread available.  ¯\_(ツ)_/¯

You could try use Precise Parts "generic filter 54mm" because the thread lengths seems longer. The real question is are M54 threads the same as "generic 54mm filter"?

 

Peter



#21 deepanshu29

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Posted 21 September 2020 - 12:50 PM

You could try use Precise Parts "generic filter 54mm" because the thread lengths seems longer. The real question is are M54 threads the same as "generic 54mm filter"?

 

Peter

That's not too long either, Precise Parts confirmed that to be 3mm long. Also, can confirm that generic M54 is same as QHY or Tak M54. I purchased a generic M54 adapter from Cyclops Optics. No issues. Can't imagine why Precise Parts would be different. 



#22 bokemon

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Posted 22 September 2020 - 09:27 AM

Here is a sample M54-to-2" nosepiece. I only see two threads!!!!!

 

 

Peter

That's because it's supposed to thread on the front face of a filter wheel and if the threads were longer they would start intruding on the inside.  Also, the threads are very fine pitch, so only requires a small triangle on the lathe bit.
 


Edited by bokemon, 22 September 2020 - 09:28 AM.



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