A minor but weird problem with filterthread

[Robindonne]

Last night i wanted to use the lens-part of my 2x barlow in a binoviewer, instead of the 1,6x that came with the binoviewer.  No problem, it fitted and worked properly.   Later i tried to fit that same 2x lens-part in the barrel of an eyepiece, but it didn’t fit for some reason. So put the 2x back to the binoviewer and tried the 1,6x in that eyepiece, but it also gut stuck after 1/2 turn.  The only solution to use that 1,6x with that eyepiece was to put the 1,6x in the barrel of that empty barlow, and again it didn’t fit.   

the strange thing is that both the 1.6x and 2x fit perfect in the bino.  

Whit all the attempts the lens was perfectly parallel and carefully tried to screw in.  But they definitely got stuck.  

I tried a filter in that eyepiece but it also got stuck.   

I have a lot of mediocre eyepieces that all accept the filters and just a handful more premium ones.  This happened with a Takahashi eyepiece.   
it didnt accept the barlows and the filters.  
the thread in the barrel looks like its never used.   
 

is there a chance of differences among filterthreads, like e.g. the m49x1 and m49x0,75 thread?  Or do i have to use some force?
 

 

Edited September 15, 2020 by Robindonne

[markse68]

I think there’s a lot of variability with no real standard and add to that tolerances! I think the Americans use an imperial thread, then there’s the metric thread, then Baader decided in all their wisdom to add a third to the mix- a sort of in between pitch that they hoped would fit both. It’s a bit of a mess really!

[Merlin66]

Yeah, not all filters fit everything!

As mentioned there's no real standard.......

Edited September 15, 2020 by Merlin66

[Robindonne]

Ok.  That I didn’t know. Thx.   

[SiriusB]

 

"is there a chance of differences among filterthreads, like e.g. the m49x1 and m49x0,75 thread?  Or do i have to use some force?"

No don't use force.

there's supposed to be a standard ~M48x0.75 for 2" Ep's & M28.5x 0.6 for 1.25" Ep's.

But as Merlin stated it's a bit hit & miss. Manufacturing tolerances, some manufacturers using a different thread.....etc

Read somewhere that Baader somehow make their filter threads a bit non standard such that they will fit pretty much anything.

If it's any consolation, last night a 1.25" filter wouldn't thread onto the EP i was using,

has fitted all other Ep's to date including ones from the same manufacturer!

This was more down to lack of thread length on filter than a different thread pitch.

So yes,it can be a bit frustrating.

 

[RT65CB-SWL]

The only e/p I have filter thread issue is my TeleVue 6mm Radian. 

My other TV e/p's and other brand e/p's are OK.