Adapter threads

[dark knight]

Can we please have a sticky for all the various threads we may come across,  for example what does a t thread equate to, is it m48, m42 or some other thread, hopefully it may help someone other than just me when having to source compatible  adapters. 

[gilesco]

2 minutes ago, dark knight said:

Can we please have a sticky for all the various threads we may come across,  for example what does a t thread equate to, is it m48, m42 or some other thread, hopefully it may help someone other than just me when having to source compatible  adapters. 

A T-thread or T2 is 42mm in diameter, but it is not M42, the thread pitch on a T-thread is 0.75mm, whereas the thread pitch on a M42 is 1mm, so if you were to try to mate a T-thread with a M42 you would probably shred the threads on one or both.

[AKB]

10 minutes ago, dark knight said:

Can we please have a sticky for all the various threads we may come across

This has the potential to be quite along list.  Aside from the plethora of threads on optical components, I get completely flummoxed by metric vs. Imperial threads on bolts and dovetails.  Nightmare!

[Astrid]

Well, I have the same issue! I just bought a canon DSLR and I have a T2 thread (from the 1.25''to 2''adapter) but no idea what T-ring I should buy for the camera.

Edited November 17, 2020 by Astrid

[gilesco]

I had mused about a website where people could upload imaging train configurations for various equipment, all with the right backfocus etc... Perhaps with a peer voting and comments section.

[fifeskies]

So many threads look the same and are very close in size (maybe only having a pitch difference on the thread as mentioned above.)

There are a lot of cheap Chinese adapters available that are at the very least good to check which is which. I use a permanent marker to label them (or for smaller ones tag them in a jiffy bag.)

Just be very gentle as you try them out as fine threads are so easily ruined , and a quick wipe of them first with a soft cloth is always a good idea.

Check them for visible damage too.

 

Once I find out what thread needs adapted to another I may then order up a better quality adapter if it is an important part of my imaging train.

Having test items takes out the guesswork.

Same applies to screw sizes , with the old metric vs imperial chestnut often appearing

 

 

 

I have a box full of various adapters so I can try to match up any thread.

 

 

 

[Second Time Around]

48 minutes ago, dark knight said:

Can we please have a sticky for all the various threads we may come across,  for example what does a t thread equate to, is it m48, m42 or some other thread, hopefully it may help someone other than just me when having to source compatible  adapters. 

There's a very good article explaining just this on the website of US retailer Agena Astro.  Lots of other good explanatory articles there too.

 

Go to https://agenaastro.com/articles/guides/miscellaneous/astronomy-threads-explained.html

[AKB]

6 hours ago, fifeskies said:

So many threads look the same

Oh, when I started reading this, I thought you were talking about forum threads... 

[KP82]

The majority of the FRs/FFs on the market have either M48 (for 35mm full frame) or T2 (for APS-C or smaller) male thread at the camera end. So when you buy extension tubes for backfocus spacing, you only need to look at either M48 or T2 ones plus a M48 to T2 step-down adapter if required.

However at the telescope end of the FR/FF there are so many different thread sizes. I've seen M63 (2.5"), M75 (3"), M83, etc. You will need to find out the thread size on your focuser drawtube and then get the right adapter.

Edited November 18, 2020 by KP82