1/4" 20t or 3/8" 16t

RalphLambrecht

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Ian Grant said:
Many tripods don't (& can't) use a 3/8" thread these days and adding an adaptor is adding a weaker link.

Ian
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I don't think that 'weaker link' is significant. Let's take one of the major tripod manufacturers as an example. Manfrotto tripods rely on an adapter system. Their tripod stands feature a 3/8" thread onto which you add an adjustable tripod head of your choice. Their heads feature a 1/4" for the smaller models (roughly 2-6 kg, some 8 kg of max load) and both 1/4" and 3/8" for the larger models (6-12 kg of max load). Apparently, they also increase the thread size with the size and weight of the camera and lens, but accomodate for cameras limited to the 1/4" thread.

I would stay away from tripods limited to 1/4" threads.
 

Steve Smith

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I have just had a look at my three tripods. The first, an aluminium set of legs with no name (the sticker has come off!) has a 1/4" male thread onto which is mounted a Manfrotto 115 three way head which has a 3/8" thread with a reducer fitted.

My Velbon tripod and Velbon head have the same reducer arrangement but my old Linhof tripod inherited from my father is 3/8" all the way.


Steve.
 

RalphLambrecht

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Ian Grant said:
That means staying away from most modern tripods

I'd be more inclined to be worried about the overall build quality of the tripod itself.

Ian
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No, it doesn't. I get both with my Manfrotto tripods.

What brands are you referring to when you say 'most modern tripods'?
 

RalphLambrecht

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David A. Goldfarb said:
What's the shear strength of a 1/4" steel or even brass bolt?...
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David

Threaded fasteners are not designed for shear! They are designed for friction while considering the tensile strength of the bolt. A well designed joint is never exposed to any shear.
 

Ian Grant

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rtbadman said:
I'm using a QR plate that offers both a 1/4 and 3/8 screw. And isn't bigger better.
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Our choices are governed by the camera manufacturer and the tripod makers.

In commercial life cameras where usually adapted to take the more universal 1/4" tripod bush, because assistants (or photographers) would loose one or the other of the two tripod bushes on location

I've seen it happen.

Ian
 

Ian Grant

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RalphLambrecht said:
David

Threaded fasteners are not designed for shear! They are designed for friction while considering the tensile strength of the bolt. A well designed joint is never exposed to any shear.
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The Ford made drive coupling on my Alfa Romeo sheared Took the brakes out in the process !!!!!

The bolts that sheared weren't far different in size to tripod bushes.

But tripod bushes don't come under that kind of stress.

Ian
 

David A. Goldfarb

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Hunting around on the net, the safe working load for a 1/4"-20 grade 2 bolt (i.e., an iron bolt of lower quality than most tripod screws, though perhaps stronger than the brass sockets on wooden cameras) is 160 lbs. Seems like most cameras are likely to fit in that range, even accounting for leverage with long bellows extension or a long lens. My Arca-Swiss B2 head is rated for a capacity of a mere 150 lbs.
 

David A. Goldfarb

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It's also not as if surveying equipment is heavier than a large format camera. Looking at theodolites on Amazon, they seem to weigh 5-16 lbs., and they don't have large levers attached to them like camera rails, so I suspect that the 5/8" thread is also a matter of convention there or maybe extra protection in case the tripod gets knocked over on a construction site.
 

RalphLambrecht

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Most likely. Pretty much like the convention to have larger tripod threads on larger cameras. Nobody said 1/4" is not strong enough. Camera designers just seem to have a preference for larger threads on larger cameras. It makes sense to me.
 
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RalphLambrecht

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Ian Grant said:
The Ford made drive coupling on my Alfa Romeo sheared Took the brakes out in the process !!!!!

The bolts that sheared weren't far different in size to tripod bushes.

But tripod bushes don't come under that kind of stress.

Ian
Click to expand...

See! Told you to watch those thread sizes!

So, what brands of tripods are you referring to as 'most' with 1/4" threads?
 

John Koehrer

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RalphLambrecht said:
See! Told you to watch those thread sizes!

So, what brands of tripods are you referring to as 'most' with 1/4" threads?
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Velbon, Vivitar, Slik etc I don't think have ever been considered "real" professional tripods. Most modern tripods now come from Best Buy or other big box photo stores.

Manfrotto, Gitzo, Feisol & other makers who aim for the advanced amateur-pro markets use the 3/8-1/4 reversible stud because they don't know what head you're going to put on it.

The more traditional tripods like Tiltall & Quickset used 1/4" screws on the head but didn't have interchangeable heads. Majestic & D&S used their own tubular mount.

End result? It is what it is & that's what it is!
 

RalphLambrecht

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John

Thanks for the line-up. I'm familiar with those brands and agree with your classification, but I was really interested in finding out what Ian meant with 'most tripods use 1/4" threads'. Reason being, we often call 'most' what we own or are familiar with, without knowing what 'most' really means statistically. For example, I'm most familiar with what you call the advanced-amateur-and-pro market. In that market, 'most' tripods are not limited to 1/4" threads.
 

John Koehrer

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Hey Ralph,
I really don't know what he was referring to with the modern comment either. But I think the most common way to buy a tripod with a 1/4" thread is the big box store. Few of them carry anything with a changeable head so the description would seem to fit.
 

richard ide

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I bought a Wild theodolite tripod. It had a 5/8" screw for clamping the instrument. I just changed the 5/8" screw for a 3/8" and clamp the camera to the tripod by tightening a 3/8" wingnut. I am qiute sure that I could stand on it.
 
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Curt

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You are very welcome indeed, I think we all learned something new.

Curt
 

Ian Grant

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RalphLambrecht said:
So, what brands of tripods are you referring to as 'most' with 1/4" threads?
Click to expand...

Slik, Manfrotto, Gandolfi are the main 3 I use, all professional tripods and none of my tripods has a 3/8" option without buying a different head.

There was a time when more tripods came with two inter-changeable tripod bushes.

But John's right these days most tripods get sold with a 1/4" fit head, and only the few remaining professional dealers and top end stores sell heads & tripods separately, and even they usually sell tripods with a standard pan/tilt or ball head as a package.

Ian
 

John Koehrer

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Ian,
You were referring to the heads? I was referring to the mount for the head :]
 

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bdial said:
Or else, it's to frustrate photographers looking for sturdy, cheap tripods at the home centers.
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If I were being more cynical than my usual self, I'd agree with you; but the answer is probably far less insidious. I've looked at some of these tripods sold at home center stores, and aside from the mounting hardware, really aren't that good for photographic use. I'd say that sturdiness is probably the most compelling reason. Surveyor's theodolites depend on very accurate positioning and need to be very stable. A 1/4 x 20 thread isn't going to cut it.
 

Steve Smith

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fschifano said:
Surveyor's theodolites depend on very accurate positioning and need to be very stable. A 1/4 x 20 thread isn't going to cut it.
Click to expand...

Unstable tripods usually have problems other than the thread size. As long as the screw holds the camera firmly to the base plate there isn't going to be any noticable difference between 1/4" and 3/8".

These unstable tripods usually suffer from flimsy legs and clamping systems which do not clamp too well.


Steve.
 

premo

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I want to thank everyone.

For the education on this subject. Why? Because hanging around camera stores in Hollywood, Chicago, and Boston, I have never seen a tripod with any thing other quarter-twenty mounts on them. I have German cameras with 3/8 fittings, but I had assumed that was the European standard. AND I( had no idea these were Whitworth fittings! I thought whitworth fittings were made to frustrate American motorcyclists who owned Ariel scoots!
 
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