View Full Version : Help request about compendium screw thread

21-Nov-2008, 13:58
Hi, I need some help that only american or english people can give me (I believe).

I'd like to know what kind of thread size is the female hole that holds the
compendium screw in my old/new Omega View 45C camera (that I believe to be the
same as Toyo 45C). I am italian, and here in Italy it is hard to find the way to
"measure" such a little female thread - we use almost exclusively metric screws.
The question is in order to try to adapt the ShenHao compendium that still I
have to the old Omega LF camera that I have recently bought from USA.

I am sure it is NOT UNC 8-32 (but very similar), and that it is not metric.

Can someone help me please?

robert fallis
22-Nov-2008, 01:00
I'm not sure about the camera's you ask about, But the normal thread is 1/4" whitworth thread at 20 turns per inch, the other thing to do is to tap out the holes to the thread you use,and match up your tripod thread as well


22-Nov-2008, 07:01
Thank you Bob, but it is not possible. 1/4"-20 Wth is the standard camera-tripod thread, isn't it? The screw to fit the compendium onto the front standard of my monorail Toyo 45C is smaller, about 3/8" (the hole, including thread: about 3.9 millimeters i.e. roughly 5/16". The screw, including thread: about 4.5 millimeters i.e. a little less than 3/8"). I prefer not to tap the standard if I can manage otherwise, with some help from colleagues. Any other suggestion, please?

robert fallis
22-Nov-2008, 10:50
here is a link to most avaiable threads that may help. Remember that you can get metric fine threads.whch are finer that standard metric threads it sounds to me as if it may be one of these http://homepages.tesco.net/~A10bsa/intro.htm


Struan Gray
22-Nov-2008, 13:42
I'd guess a No. 1 BA. The BA threads were common on technical and scientific instrumentation, and 1 BA fits your diameter measurements very well.

Workshops will often have a set of BA thread gauges, even if they don't have the taps and dies (the tools you use to cut threads), so if you have one nearby it's worth asking. BA threads were not used much in cars, so your local MG or Jaguar owners' club probably won't have much, although in general English classic car clubs are good places for Imperial measurement tools. BA threads were used a lot in modelmaking, so if you have a local modelmakers' store or club that may be able to help.

All that said, a pack of bolts or nuts, or even a tap/die set, are not so very expensive. Serious tool suppliers here in Sweden have BA sets in stock, although the DIY and hobby retail places don't.

23-Nov-2008, 14:01
Thanks to both of you. From your suggestions and measuring accurately the threaded hole I have concluded that I have one of these sizes:
1 BA or BSF 7/32 or ISO special 5.5
All of them seem to be very similar, with a pitch of about 0.9 millimeters, so any of them
will probably fit. I have just seen some dies and taps on eBay and I will buy one of each. I will also search for a thumb screw of thati size, but non on the bay (found none).
Many many thanks

23-Nov-2008, 14:10
For Struan, apart from LF (if the forum policy allows that):
maybe sometime we'll meet, because I too love Achnahaird and the Coigach, and your images deeply touched me. But from here in Italy the western Highlands are a long way...
Saverio (Narcissus)

Struan Gray
26-Nov-2008, 08:26

Please excuse the delay in replying, and thank you very much for your appreciation of my Scotland photos. I shall be in Coigach again this summer, so if you are in the area late June through July do get in touch. We'll be at Achnahaird Farm.

I hope you find the right thread.