Metric vs imperial threads

[pmrid (Peter)]

Who remembers that satellite that got confused by this. The Mars Climate Orbiter back in 99.

Well I’m having my own little experience of much the same thing.

I recently bought a C11 with the idea in mind of swapping some ZWO accessories over to it - specifically an EAF. They’re pretty easy to fit - right?.

I bought an adapter for a C11. Lovely bit of kit. Designed, I believe, by our mate Don from B’tel.

It turned up and included a flexible coupling with a 5 mm side for the EAF and a 23(or so) for the C11’s focuser shaft.

Trouble is, this C11 was built differently. It has a 19mm shaft. So a call to Don who was able to source a replacement which arrived (some $$) later but the genie was not finished with me yet. Turned out the brass coupling screws onto the focuser shaft and - you guessed it, the replacement has the wrong bleedin’ thread.

My next stop, assuming Don’s party won’t now be able to find an imperial thread replacement, will be to go to an engineering outfit and invest several hundred smackers and wait several weeks if not months for the replacement. You just have to love this hobby or it would send you nuts.

[astro744]

My immediate thought with 19mm is 3/4” which is 19.05mm. The pitch of the thread is likely too imperial being so many threads per inch.

There are many fields where metric and imperial units mix and astronomy is just one of them since parts are sourced from all over the world.

Would you believe that airspace over a few (large in area) countries is metric with the remainder of the world imperial!

[I.C.D (Ian)]

Hi Peter next time you get stuck with the wrong size bolts see if can find a company that only sells nuts and bolts only like (K&C Harris) Maitland NSW if they can't help you then you are in trouble.
Ian

[croweater (Richard)]

Hi Peter, if you want anything made up Joshua Bunn can do it.
Cheers, Richard

[leon]

Hi peter as mentioned there are heaps of specialist bolts and fasteners that would have exactly what your after, they specialise in this sort of stuff.
Just my two cents worth.

Leon

[xelasnave]

Hi Peter.. get yourself a tap and die set...experiment on some scrape and when you find out how easy it is to do you may find you can solve the problem all by yourself...I think you will be surprised just how simple it is to made your own bolts and nuts etc...get on google and see what you can buy and just how inexpensive these tools are these days.

alex