Extending Rise on Sinar Norma Front Standards

[Struan Gray]

OK, my thread gauges are a commute away, but my camera is here, so I unscrewed a black knob and it fits perfectly into the 3/8 socket in the bottom of various cameras and tripod heads.

I don't know what the reason might be, but I sincerely doubt it was a lack of tooling. My grandfather built Seafires during WWII, and although machine tools were hard to come by during the War (and aluminium stock like gold dust), both were freely available later as war stocks were wound down. Switzerland would have had no trouble getting hold of the required dies and taps. It's more likely that Koch wanted it to be possible to screw standard spigots (for flash equipment perhaps?) into the tops of the standards. I have never seen a Sinar publication advocating anything other then the systems of rods, but you never know.

I suspect the standard upright and its foot were made in one piece for stiffness. A socket would have been needed otherwise, and that and a bolt would have added to the bulk. The flared out portion (needed to provide enough friction to lock tilts) prevents the standards coming close together as it is.

As for the diameter, i suspect the surface finish on extruded rod wasn't good enough for smooth operation, so any upright needed to be machined to tolerance (another reason for making the upright from oversize stock). Then, my experience is only anecdotal, but the instrument makers I worked with at a lab in Berlin used to ream holes to nominal size and use slightly undersized shafts. I was taught the opposite in my (UK) school machine shop, but reamers come in undersize/oversize sets, so I don't suppose it's an absolute rule, even in ISO-land.

[mdarnton]

Excuse me if someone has already mentioned this, but several weeks ago in another thread someone mentioned that 3/8x16 is for all practical purposes functionally identical to the related 10mm metric thread over the short distances that we usually thread camera stuff, which may account for its common use in camera fittings. 3/8 will fit 10mm better than 10mm will fit 3/8, though. Apparently.

[Sean Mac]

The BSW 3/8 x16 and the UNC 3/8 x16 are close.

British Standard Whitworth is 55 degrees angle and Unified Coarse is 60 degrees. The BSW has rounded crests and roots and is therefore a stronger form than UNC which has a flattened crest and root. A thread gauge and good light is really needed to be sure.

The Swiss do funny things. I have a Schaublin lathe with 6.35x1mm feedscrews

The Swiss machine tool industry has roots in Massachusetts strangely enough. So an American thread form is very possible.

[RSalles]

Not sure if it's about these extension rails you're talking about:

https://goo.gl/photos/2LerRFf9cvtxM2Fw9

Are that?

Cheers,

Renato

[Leonard Robertson]

My findings based on a couple of M10X1.5mm bolts and a couple of 3/8"X16 bolts (limited sample in other words) - 3/8" bolts thread into M10X1.5mm nut, but the fit is pretty loose. Sinar upright cap is also quite a loose (almost "sloppy") fit into a 10mm nut. I can't get either 10mm bolt to thread into a 3/8"X16 nut. The metric bolts are used ones, but they thread into a new 10mm nut just fine. Measuring the outer thread diameter of both 3/8" and 10mm, the 10mm is about 0.016" larger than the 3/8". If anyone has nuts and bolts to try this, please see what sort of results you get.

There is information here on Whitworth tripod threads, under "Screw thread":

https://en.wikipedia.org/wiki/Tripod_%28photography%29

I never knew there was a 3/16X24 BSW tripod thread.

I tried a couple of screw pitch gauges (one a Starrett and one a Miller Falls) and on the Sinar upright cap thread. To me it looks like it is a 60 degree thread. But I don't have a 55 degree Whitworth pitch gauge for comparison, so I can't say for certain. If anyone has a Whitworth gauge I'm curious what you see.

Len

[Struan Gray]

The Swiss do funny things. I have a Schaublin lathe with 6.35x1mm feedscrews

That's almost as much fun as the occasional left-hand threads and non-standard bolt heads secreted at odd points around 1970s British cars.

I've worked a lot on Ultra-high vacuum systems, where US and Metric equipment is compatible in terms of flange sizes, but the bolt sets are often different. There, the engaged length of the thread is long enough that there is a clear difference between 10 mm and 3/16. Mixing and matching will just lead to a jammed or rattling bolt or nut, and a leaking vacuum seal. The bolt heads are different enough that for reliable torque setting you need the correct spanner.

That said, there are surprisingly many mixed standards. The BA fine thread series was very influential, and for a long time Europeans would sometimes use bolts with metric head sizes and BA threads. The ISO M-series has pretty much taken over for coarse threads these days, but there are still oddball historical throwbacks like the tripod threads, garden hoses and plumbing and compressed gas fittings. There is a surprising amount of science to the design of a screw thread, so there are often good reasons for being conservative.

[Jerry Bodine]

There is a surprising amount of science to the design of a screw thread, so there are often good reasons for being conservative.

FWIW, my Sinar publication titled The SINAR Construction-Unit (undated, from around the time I bought my Normas in the late 60s) identifies the Pan-Tilt head's screw that secures the camera as Camera Screw, German 3/8". It also describes a bushing that can be installed in the bottom of the head (at tripod attachment) that is identified as Reducing Bushing German/English. This may not be much help in our discussion and may cause further confusion.

My experience in the aircraft industry for many years has taught me that there are separate tolerances for the screw thread and for the tapped hole that it's intended to be inserted into.

[Leonard Robertson]

I'm an amateur machinist with limited skills (at least I own a lathe and a couple of mills. Maybe it is a stretch to claim to be any sort of machinist). A few weeks ago I saw a YouTube video on changing just two gears on a my 9" South Bend lathe in order to cut many metric thread pitches with an error of less than 1%. I got the gears and last week cut my first metric thread. I'm missing a Norma upright cap so one project I planned was making a new approximation of a cap. You can probably see the irony here. The first part I need to make for my European camera needs to have an Imperial thread. Fortunately the gears are easy to change back to the standard ones.

Renato - To me the pieces in your picture look to be the upright extensions. I didn't realize they were red in color or there are two different lengths. I assume the ball and socket pieces are to run horizontal stabilizer rods from the top of the front and rear standards. I need to get out my Norma catalog and study up on these parts.

Len

[Jerry Bodine]

Len -
If it's any help, there are some closeup photos of the stabilizing rods, riser end caps, and clamps for the rods that screw into the risers and rear standard. See them on the Glennview website:

http://www.glennview.com/sinar.htm

He should be able to confirm the thread size for you; he makes a lot of parts himself.

[Struan Gray]

Jerry, I now work part time with translations, and you would be amazed what English-as-a-second-language technical folk will sometimes insist is the correct English for a word or phrase. Don't forget, the Norma manuals were the ones advocating using the 5x7 system box as a rucksack :-)

Len: if you have the bolt hard-anodised, you may find it binds, as the anodising adds a thickness. Most places that do that kind of work can tell you how much to undersize the part. (It's not much, but it can be significant).