Compound shutter sizes

[Ole Tjugen]

Since these come up quite often, I'll post what information I have here once and for all.

All data are taken from the Compur Repair Manual, so they should be correct.

There were five sizes of Compound shutter (late type, with X-sync):

Compound 3-X Tube 7
Compound 4-X Tube 9
Compound 4-X Tube 10/II
Compound 5-X Tube 12/I
Compound 5-X Tube 12/II

Dimensions are listed as:
A: Cell thread (all are the same front and rear), all are 40 t.p.i.
B: Flange thread
C: Largest aperture diameter
D: Body diameter
E: Length
F: Mount depth (flange to rear end of shutter).

Data - all dimensions in mm :

3-7 : A: 55.69 B: 60 x 29 1/13 t.p.i. C: 40 D: 87 E: 37 F: 15.7
4-9 : A: 62.20 B: 65.9 x 29 1/13 t.p.i. C: 52 D: 106 E: 50 F: 21.8
4-10/II : A: 67.92 B: 76.7 x 29 1/13 t.p.i. C: 52 D: 106 E: 45 F: 19.3
5-12/I : A: 82.77 B: M90 x 1mm C: 64.5 D: 125.5 E: 74 F: 33.2
5-12/II : A: 82.77 B: M90 x 1mm C: 64.5 D: 125.5 E: 60 F: 25.2

Fastest shutter speeds are: #3: 1/100 #4: 1/75 #5:1/50

[Ash]

Ole, you best link to this thread in your signature. That way people can always refer to it

[Ole Tjugen]

Good idea, Ash.

[Struan Gray]

Nice idea Ole. Are those thread sizes 'really' t.p.i., or are they metric sizes translated into imperial units?

[Ole Tjugen]

Those thread sizes are really t.p.i.

Those are the data taken directly from the book, and thus from the original specifications. The 29 1/13 tpi is very close to .75mm, which is what SK Grimes use.

The 40 t.p.i has a 64° pitch, the 29 1/13 t.p.i. has a 50° pitch. Don't ask me why...

[Struan Gray]

47.5° is the old BA standard for fine screws and bolts. The thread profile was used for wide-bore precision threads too, so I suspect the 50° comes from there.

64° seems odd, but then instrument makers are a funny bunch.

[Bemko]

The 29 1/13 tpi is very close to .75mm, which is what SK Grimes use.

I believe that 29 1/3 TPI is actually closer to 0.9mm than 0.75mm. It can be easily calculated: 25.4mm/29.334=0.866mm

I can also confirm this by measuring the outer thread of my Compoud #3 shutter - it has 5 threads over ~4.5mm, which gives 0.9mm.

The table from this site http://www.suaudeau.eu/memo/pratique..._centraux.html also supports this measurement.

[David Lindquist]

I believe that 29 1/3 TPI is actually closer to 0.9mm than 0.75mm. It can be easily calculated: 25.4mm/29.334=0.866mm

I can also confirm this by measuring the outer thread of my Compoud #3 shutter - it has 5 threads over ~4.5mm, which gives 0.9mm.

The table from this site http://www.suaudeau.eu/memo/pratique..._centraux.html also supports this measurement.

Yes, the SK Grimes website shows a pitch of 0.9mm for the flange/retaining ring thread on those Compur and Compound shutters described elsewhere as having a pitch of 29 1/13 threads per inch. I expect Ole was mis-speaking. Incidentally it looks like his last activity here was just about two years ago.

I have no idea why such an odd pitch was used; years ago I asked Steve Grimes. He didn't know either.

David

[Mark Sampson]

Is it time to put this info up on the front page of this site as article? That would save peole searching for it.

[Ole Tjugen]

I'll add the three types of "standard" Compur 2, too - same format as above:

Compur 2-X Tube 5/I
Compur 2-X Tube 5/II
Compur 2-X Tube 6/II


2-5/I : A: 45.8 x 40 t.p.i. B: 50 x 29 1/13 t.p.i. C: 35 D: 80.5 E: 35 F: 14.6
2-5/II: A: 45.8 x 40 t.p.i. B: 50 x 29 1/13 t.p.i. C: 35 D: 80.5 E: 25 F: 8.3
2-6/II: A: 49.65 x 40 t.p.i. B: 55.8 x 29 1/13 t.p.i. C: 35 D: 80.5 E: 30.8 F: 12.2