Hi all. I sometimes have the situation where I have screwed on a bit of kit and later find it very difficult to unscrew it even though I didn't excessively tighten it. Spacers seem the worse as there is not much to grip. On a couple of occasions I have had to use a multigrip wrench and put on a lot of force. This is a bit dangerous when you are trying to remove a 10mm spacer from your camera and I am concerned I might distort the metal.
Get one of those plastic wrenches with the rubber adjustable strap that wraps around the item and leaves no mark. Bunnings has them.
I smear a thin amount of Teflon grease on threads of some adapters that are prone to that. Takahashi connections are the worst for this. Their black coating seems especially dry and high friction and they must have more threads per centimetre.
A multigrip wrench distorts the filter or whatever is stuck. You can buy
devices that tighten all the way round the object rather like a miniature oil filter removal tool. I believe that some camera shops sell them, or have a look in photographic accessories on ebay.
raymo
Unfortunately much astro gear is made from Aluminium/Stainless Aluminium/Aluminium which galls when screwed together tightly.
We used to see a lot of this in fighter aircraft and used specific copper synthetic greases, but, these would be not much use in an image train. Maybe a silicon anti-size grease but used sparingly. I use a zinc anti-size grease on car parts...the philosophy is the same. The anti-size ...in this case...has small spheres of the zinc which squish in-between the surfaces. Allowing a lower friction surface contact.
But as said...in astro gear a very small amount would suffice due to the fine threads.
This also worked a treat on my mount, G11 clutch knobs. Stainless and alloy, the zinc anti-size freed it up enormously. But hey that was a large thread....YMMV!
Yes i know what you mean, and have experienced what you mentioned, I found the best way is not to hold the spacer/filter or any small circular item tightly at all, it is best to have a light grip, and better still to lay it in the palm of you hand and with light force turn in the removal direction.
For the last twenty years I've successfully used a light smear of boot polish on filter threads etc. (your choice of colour)
Doesn't melt like some greases or outgas onto optics.
I strongly recommend it!
(Wear rubber kitchen gloves with the two jammed parts squeezed between the palms of the hands, a good twist usually frees them up without marking)
I often wonder if the locking is caused by poor quality machining.
I bought some cheap eBay adapters to suit some DSLR camera where the thread is clearly torn up rather than cleanly cut, (bearing in mind that the thread cutting process is in fact a tearing process !)
This is usually caused by using incorrect cutting speeds, feeds and depths of cut, poor lubrication, inadequate swarf clearnce and also cutting tools that arent sharp.
Threads cut where the swarf has got caught up in the thread that has just been cut, actually causes the hairlike fine strands of swarf to be friction welded back onto the thread thats just been cut and this can lead to additional galling and seizure.
A good thread for our sort of optical threads - eg extra fine pitch, ought to have a high quality surface finish, it should look almost shiny.
So while this is hard to fix once you have it - its possible to use a small amount of fine cutting compound and repeatedly tighten and loosen the thread, so as to slightly polish the surfaces but this only works if you can clean the thread afterwards - so not practical for most situations
It also will not necessarily prevent galling if the two metals on either side are either the same material or are soft material - aluminium being a prime culprit.
An ideal thread combination is a hard and soft material (eg Stainless and phosphor bronze) on each side - this becomes self lubricating, but we rarely find this.
The other problem which I unfortunately had first hand experience with on some expensive equipment is that not all threads are correctly made
That is the diameter, pitch and the form may not have been cut exactly the same
One thread may have been cut on one type of machine eg lathe - using one type of tooling and the other thread cut on a milling machine using helical thread cutting
So its no wonder that sometimes two threads that ought to be mating are not properly mating.
Trouble is you may not even know it.
In my case a $1700 focusser.
The thread machined into the body was cut incorrectly (too small and incorrect tooth form) and I had to recut a thread on the adapter that was made correctly to fit it !
I couldnt recut the thread in the focusser because it wasnt possible to dismantle it or hold it in a lathe to recut it.
