1/4" Tripod Thread on 8x10

My Deardorff 8x10 is equipped with a 1/4" tripod thread, which seems to be greviously small for such a large camera. Is this common to all Deardorffs, or just some of them? I've been trying to think of ways around this potential weakness and haven't had much luck. I thought about taking it to a machine shop and having a 3/8" thread milled, but am not sure if that would work. I also thought about trying to use something like an Arca Swiss type QR system to reduce wear on the thread, but am not sure how good of an idea it would be to use such a (comparatively) small mounting surface to support an 8x10 (those QR plates aren't exactly huge). Any ideas? Many thanks in advance.

The 1/4" thread was standard for many decades. You are correct, it's

pretty flimsy when you consider the potential weight it has to hold.

Consider a 3/8" fitting called a "T" nut which can be installed either

in place of the present 1/4" fitting or adjacent to it. These are

available at high end woodworking suppliers and come in various

depths. It's a relatively simple installation.

I actually had considered doing the T-nut thing. I've used them

successfully in a number of other projects. However, I'm a little

wary of boring holes through the bed and the big metal bed plate on

the bottom of the camera (who wouldn't be?). I'll keep it in mind,

though, as other suggestions (hopefully) come up.

What is the size of your tripod head platform? A big platform like

those on the big Majestic heads and Ries heads will distribute

the torque and pressure better than a smaller head.

Kirk makes a fairly large camera plate for the Arca Swiss head. Mine

is probably 4" x 3" which isn't huge but is a good bit larger than

any other one that I've seen. AFAIK, you can get it in either 1/4 or

3/8. However I'd be a little leary of using the Arca Swiss head with

an 8x10, at least one that weighs what the Deardorff does.

My tripod head is the previous version of the Gitzo 1570 low profile

head. The platform is rather large, about 3.5" by 6." However, I

shoot a lot of stuff on the ground, so I'm thinking that even with

that big of a platform, shooting down at the ground might put a

sizable amount of stress on the mounting screw. I can't be sure,

though, as I haven't done the math.

To put your fears to rest, consider that a 1/4-20 has a gross area of

.049 square inches, and a decent bolt may be made from 20 ksi steel,

or higher. This results in an allowable tension of close to 1000

pounds! If your camera is able to strip out the bolt, then something

is going seriously wrong.

 

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Now, if the baseplate is aluminum, then you have a much weaker

material in the plate, but you should still be able to apply 300-400

pounds of tension to the threads in the baseplate.

 

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It is important to make sure the bolt and the plate are completely

theraded together, and to be careful to make sure that you don't

cross-thread the baseplate. Although the baseplate has sufficient

strength, if you apply significant stress to an individual thread, you

will strip it, because aluminum is a fairly weak material in shear. I

mention this because some mounting plates, like the Bogen hex plates

with the hand-tighten collars on the bottom, will permit you to screw

the bolt in only partially, and then crank down on the tightening

collar on the bottom. This could end up stripping out a portion of

the threads in the camera baseplate.

 

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Don't worry about the threading, it's completely sufficient. However,

the fact that there is only one connecting point on a camera so large

is a problem, because the torque that you can apply to the camera can

be quite significant. The torque is a function of the force applied

multiplied by the distance from the pivot point (the mounting bolt

location). What this means is that you have to have the camera and

tripod screwed together very tightly to ensure the camera won't turn

on the tripod.

 

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The easiest way to avoid this is to have two connecting points. This

will eliminate the possibility of rotation, and make the camera

completely fixed on the tripod. I use several Kirk plates on my

cameras. My 7x17 has a 4"x4" plate with two bolts into the camera. I

don't have to tighten too tight, just enough to keep the plate snug to

the camera and to ensure the bolts won't loosen during travel. You

can get the plate with a single bolt, and possibly with a hard rubber

interface to increase the coefficient of friction between the

baseplate and the adaptor. This might make the camera sufficiently

connected to avoid rotation. If not, the plate is designed with a

slot, so a second bolt can easily be added. You will have to drill

and tap the camera, though.

After a bit of thought, I've come up with the following solution. My

tripod head has space for two camera mounting screws, so what I think

I may do is install two 3/8" T-nuts in the camera bed in front of and

behind the current mounting hole. Alternatively, I think I might

just put in a single 3/8" T-nut to back up the current 1/4" hole.

Nothing is final at this point, though, as I'm currently 200 miles

from home and won't be returning for another two months. Thanks much

for all the suggestions.

Dave, you might also want to consider this rule of thumb: In order for

a threaded fastener with standard threading to achieve its maximum

holding power, three full threads need to screwed into to the socket.

One possible reason for 1/4-20 on your camera might be that a 3/8-16

would not allow this condition to be met. Screwing a bolt into the

camera any further than the three thread depth will not increase the

holding power of the fastening! If you calculate the the surface area

of the contacted thread, beyond that point you will exceed the cross

sectional area of the bolt, which would break first inasmuch as it

would then be the weakest link in the chain, so to speak. A second

1/4-20 socket might be fine in preventing the camera from twisting

loose, but other than for that reason, I would concur with the previous

contributor who so eloquently attempted to put your concerns to rest.

That guy must have been a graduate of the Penn State school of

engineering! My advice is to acquire a broad area quick release

mounting plate and attach to the camera with a good quality bolt (most

come with one) using a piece of inner tube or similar rubber sheet to

keep it from breaking loose. I've done this for years without a hint

of a problem.

Hey guys, forget the T-nut thing. T-nuts are liable back out, since

they are not anchored, but rely on constant tension to hold them in

place (not the right thing for constant mounting/dismounting). If

they back out a bit and you twist on them, they can tear up the wood

on the back side where the prongs grip and then you have a bigger

repair project to do. Go to a competent machinist and have him make

you a two-piece screw-together flange assembly out of suitably strong

material with a 3/8" threaded hole in the middle, some kind of ridges

or key to hold it from turning and plenty of surface area for the

flanges. This requires only a small hole and, since it screws

together, won't back out ever. You can countersink it for a flush

mounting or not, depending on your needs and desires.

Regards, ;^D)

FWIW, modifying the 'dorf will not help it's resale value.

True enough, it would decrease the resale value. However, I'm not

too worried, as I bought this camera to use and to enjoy, not to

resell, so I doubt that I'll be selling it for a long time.

Dave: I wouldn't worry about the 1/4 in. bolt. I have carried my 8x10

Ansco for a long time over my shoulder with the camera on the tripod

with legs collapsed. That includes the weight of a 12 in. Commercial

Ektar in Ilex shutter. With the platform you have on the tripod, you

will have no problems. If the 1/4 in. mount bolt was a problem, you

can bet it would have been changed during the many years the camera

was made. You will rip the bottom off the camera before you tear out

the bolt or break it.

 

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Regards, Doug.

Here's some more on T nuts. Actually, many older wood fields have T

nuts--or a similar fastener--as the mounting receptacle. Part of the

wear and tear on a well-used camera weakens the fitting within the

wood so that, as Doug suggests, the bigger threat is not the

strength of the metal threads but the potential of tearing the nut out

of it's wooden seat. Whereas some T nuts have prongs that grab the

wood, others have screw holes for preventing the fitting from backing

out and twisting and with ingenuity one can add extra screws around

the perimeter of the fitting making a strong installation that's in

there forever. Two receptacles on a big camera make good sense as

does the rubber pad suggestions. I have done this type of

installation and it can be done neatly to have no cosmetic effect on

the camera's value.

Many thanks to all who responded to my question. I'm not sure what

I'll do, if anything, but at least now I've got a bit more

information to work with. Thanks again.

Well, sorry to worry some of you, but there is a 3 pages article on this topic in the last edition of a french photo

magazine. They said broken 1/4 screws where not so rare, especially among tele lenses users. Small screw big

damage! Considering the weight of an 8x10 and even a 4x5, I wouldn't be at rest carrying it on shoulder if fitted on a

1/4 screw! The writers of this article said 1/4 was a conservative nonsense and pleaded for 3/8 screws as a

standard.

An 11 X 14 Deardorff weighs around 30 lbs. A Ries Model A weighs

around 15 lbs. with the head. Guess what size the tripod screw is?