Tap for Tripod Thread(and general repairs)

Long story, but I had someone in the other day who knocked over my Calumet Monorail sitting on a Tiltall. The camera was fine other than it broke/stripped out out the tripod mounting hole.

 

My thought on fixing this was possibly to drill out the tripod mounting completely, epoxy in a steel bushing, and then drill and tap it correctly to size.

 

I've heard two conflicting reports on the thread size for this. Some references suggest 1/4-20, and the screws in that size I have seem to screw in fine. I've seen others suggesting it's a Whitworth thread, though...I can probably make some calls and find someone who MIGHT loan me a Whitworth tap, but obviously I don't want to go that route if it's not even correct.

 

Does anyone know this for sure?

The smaller tripod mounting thread is definitely 1/4 inch Whitworth and has a pitch of 20 per inch - according to the Wikipedia article:

 

LINK - British Standard Whitworth - Wikipedia

 

The article also says that the larger thread is 5/16 Whitworth. However I found another site which says it's 3/8 (as I had always thought):

 

LINK - Photography thread size - equipment standards - Photokonnexion

 

Edit - the second link refers to the thread as "Unified Thread Standard’ (UTS). It’s published by the American National Standards Institute (ANSI). The camera thread is a UNC specification for a ‘coarse’ thread." I suspect that UNC Coarse and Whitworth are the same, but being British, I'll stick with Whitworth.

Edited May 31, 2020 by John Seaman

I'd not trust a plain epoxied-in bushing. When you tighten it, it's almost certain to pull out. If you can knurl it, better, but I'd rather see something with a lip on top so it can't pull through. Better yet, would it be possible to use a Helicoil? Those are often stronger than the original thread.

 

Not sure about the Whitworth. The only difference is the angle, 55 instead of 60. I've always used regular 60 degree taps with no trouble at all. I wonder if anybody even uses the Whitworth anymore? I'll have to look into that.

 

BTW, I had a Calumet, several in fact, though long gone, and I still love and use my original Tiltall.

Good thought on the helicoil.

 

They're prohibitively expensive for me to buy the stuff to install them myself, but I may take the mount to mechanic and ask him to do it. Not until after he finishes rebuilding the engine in my MG, though...

 

Since the "foot" can be removed from the monorail, I wonder too if that can be purchased separately.

1/4 Whitworth and UNC are not the same but close and can be interchangeable. Hellicoil would seem the way to go and would be strong enough assuming there is enough thickness of metal in the rail. I would expect any classic auto engine machine shop to have the necessary equipment. Ebay have repair kits for £25:) which may be the cheaper option.

Too bad you're not closer- I probably have a box of 'em (non-Whitworth) plus the special tap. You can also get Whitworth ones from Amazon or eBay. I never knew they came in Whitworth so that brings up the question of what my surplus ones really are.

 

Now you've got me curious. I need to measure the thread angle on my Tiltall and see what they used. My Focal Encyclopedia of Photography, that I consider the bible of all things, lists 1/4" or 3/8" Whitworth as the two sizes, though I wouldn't be surprised if USA manufacturers used 60 degrees.

Edited May 31, 2020 by conrad_hoffman

OK, my Bogen 3001 is definitely 55 degrees. I couldn't do as good a measurement of the Tiltall, but sighting it with a pitch gage, it looks like 55 degrees too. Been at this for a lot of years and never knew that! BTW, the Tiltall was originally shipped with a crazy long tripod screw, maybe the better part of an inch. You were expected to cut it to the length needed. Edited June 1, 2020 by conrad_hoffman

Interesting discussion and thanks.

 

Funny enough, my Tiltall(Macioni Bros, so the original) has a fairly short screw. In fact, I went a long time without any covering on the top plate as I sometimes had trouble getting it to engage. I finally did put thin cork on it.

 

Part of my concern is that a piece of metal is physically broken out of the mount. I'm wondering about building that up with JB Weld before helicoiling.

 

Given the amount of British stuff my garage does(my MG isn't the only one in there now, although I'm only aware of BSF threads on the carburetors and nowhere else).

Monorails and larger/heavier cameras use a 3/8" Whitworth thread.

 

So it'll either be a 1/4" or 3/8" Whitworth thread - AKA BSW. Those are the only two current standard tripod bushes.

 

Both those taps are easily found here in the UK. They're pretty much obsolete (except for tripods!) and can be picked up almost anywhere you find old tools on sale.

 

You might even find a set of Whitworth taps on eBay.

Edited June 1, 2020 by rodeo_joe|1

Monorails and larger/heavier cameras use a 3/8" Whitworth thread.

 

So it'll either be a 1/4" or 3/8" Whitworth thread - AKA BSW. Those are the only two current standard tripod bushes.

 

Both those taps are easily found here in the UK. They're pretty much obsolete (except for tripods!) and can be picked up almost anywhere you find old tools on sale.

 

You might even find a set of Whitworth taps on eBay.

 

This one is definitely 1/4"

 

Whitworth is hard to find, but not non-existent in the US. I've had to look for it as I do own a British Leyland vehicle :)

Whitworth is hard to find, but not non-existent in the US. I've had to look for it as I do own a British Leyland vehicle

I think even BLMC used BSF or metric rather than BSW. At least within living memory.

 

It's when you get to old plumbing fittings that things get 'interesting'.

Old plumbing? Heck, I'm working on a project right now that uses BSPP fittings. It's a giant pain because not much over here uses those and the catalog descriptions leave much to be desired.

I think even BLMC used BSF or metric rather than BSW. At least within living memory.

 

It's when you get to old plumbing fittings that things get 'interesting'.

 

At least on my MG, everything is actually SAE with a few notable examples of BSF/BSW(which I'm sure you know use the same wrenches, just with a different sizing convention). The BSF fittings I usually encounter are on hydrualics(brakes and clutch). The SU carbs have SAE on the linkages. Some of the carb body uses American-type machine screw fittings(i.e. 10-32 to hold the domes on). The jets adjusters are BSF, while IIRC the throttle shafts are a 60º Whitworth-type thread with a pitch that's unique to brass. There are no metric fasteners on the car unless a "DPO" put them on. Even my engine, which is in the process of being torn down now, is SAE throughout.

 

The REALLY fun ones are the XPAG/XPEG engines used on the T-type MGs. At that time, the tooling for the lovely little prewar OHC MG engine was worn out, and they were in need of fresh tooling. BMC ended up buying an entire engine factory out of France, and found, naturally, that all the fasteners were tooled with metric threads. Under the excuse of "We don't mechanics to have to buy new tools" but probably more of a mindset of "We're British and we'll be darned if the French are going to tell us what to do"(the latter quote attribute to MG mechanic extraodinaire John Twist). So, what they ended up were engines that used Whitworth/BSF compatible threads grafted on to metric bolts.

Ben, have you considered one of those much less expensive tripod thread adapters instead of a helicoil ? Link .... 5x 1/4" to 3/8" Convert Screw Thread Adapter Tripod Mounting Monopod Camera | eBay

 

When the 3/8" hole is tapped, the adapter could be locktite'd or Araldite'd in, the Araldite being the 36hr one for maximum strength. The adapter already has the right tripod thread.

To fill a really big hole, you could use a mic stand adapter that goes from 5/8" x 27tpi, down to 3/8" BSW, and then a 3/8" to 1/4" BSW adapter.

...the Araldite being the 36hr one for maximum strength.

The fill strength of slow-setting Araldite is excellent, but I've lately been using some budget-priced quick-set stuff that IMO has better adhesion to plastics and most metals. It also sets glass-clear without having to be heated and outgassed. In any case, you don't need great strength to stop a threaded adapter coming loose, and, who knows, you may have to get the thing undone again one day.

The tripods that I know, likely cheaper than those described, have threads loose enough to likely fit either thread discussed above.

 

Reminds me of knowing, years ago, that a US garden hose, with 11.5tpi, will fit on the end of a 3/4 inch US threaded pipe with 14tpi.

This became the subject of discussion in Popular Science many years ago, after a project in the magazine used that connection.

(Note that the other way around does not work.)

Whitworth tap and die sets are available from Amaxon

 

https://www.amazon.com/Whitworth-British-Standard-BERGEN-AT045/dp/B01MQ2M3C9/ref=sr_1_1?crid=2AIO67CMNKN5P&dchild=1&keywords=whitworth+tap+and+die+set&qid=1591416538&sprefix=whitworth+tap%2Caps%2C168&sr=8-1

 

You can also get a 3/8-16 BWT Helicoil repair kit.

 

https://www.amazon.com/cortador-reparación-Whitworth-dañadas-Helicole/dp/B06Y1QKDNR/ref=sr_1_17?dchild=1&keywords=whitworth+helicoil&qid=1591416671&sr=8-17

 

BWT and ANSI threads are nearly interchangeable between cut thread versions, since the tolerance are very loose.

From: Tripod (photography) - Wikipedia

 

the ISO1222:2010 standard says UNC.

 

 

Also, that older cameras and tripods use BSW, but doesn't say more about how old.

 

But also that they are usually interchangeable.

But also that they are usually interchangeable.

 

Not if they're made to fine tolerances for other purposes such in the auto, aero or space industries, but tripod threads are made with plenty of clearance for ease of screwing them in the camera and to avoid binding or tight thread syndrome, and when un-doing the screw, they seem to be designed to "spin" out, which only a loose thread can allow.

 

The two main differences between BSW and UNC is the thread flank angles and root diameters. Machined to close textbook tolerances, the two won't screw together, but I wouldn't be surprised if they did with the the wide tolerances used for tripod threads. Without retrieving my thread gauges to check, the tripod thread looks like Whitworth to me. I'll check tomorrow. One thing I have checked so far is that my old Kodak 3A's and No4 folders readily accept late tripod screws, they almost fall in.

Yes, the quote was specifically for tripods and tripod sockets in cameras.

What is missing from this discussion on UNC vs BSW compatibility is Class of Fit which will be a higher class for auto/motorcycle engine parts, and low for tripod screws and sockets for ease of mounting. The low Class of Fit will permit interchangeability between UNC and BSW tripod screws and sockets for limited thread length. The camera and tripod fittings were standardized in the mid 60's to 1/4-20 and 3/8-16 UNC. ISO 1222:2010 applies. The Calumet is probably UNC. My Tiltall (purchased in 1990) is UNC. I concur with the recommendation to drill and tap for 3/8-16 and insert one of the available 3/8 to 1/4 reducers. A bottoming tap set may be needed. An alternative repair is to make a flat plate that matches the Calumet's base footprint, drill and tap the 1/4-20 threads in the center of the plate, and mount the plate to the base with multiple flat head machine screws.

An alternative repair is to make a flat plate that matches the Calumet's base footprint, drill and tap the 1/4-20 threads in the center of the plate, and mount the plate to the base with multiple flat head machine screws.

 

That method came into my head as well, but what ever plate was used, it would probably be too thin to have enough thread depth for adequate security. A nut could be TIG welded on the back of the plate and the plate drilled and tapped using the welded nut as a guide, or just a 1/4" hole in the plate with the nut behind it. Of course a large hole in the camera's base would need to be drilled or ground out to house the nut. The plate idea is a good one but could be a somewhat cumbersome and unsightly repair for a monorail camera.

Alright, thanks to everyone for an informative and productive discussion, but I feel like a bit of an idiot.

 

It seems as though there's an easy fix to my immediate problem...looks like I should be good to go with a replacement bushing.

 

 

 

+1 for replacing the bushing.

 

WRT to custom mounting plates, aluminum bar stock in widths that match the base in 1/4" or greater thickness is available from the river site or online metal suppliers. Hardwood plywood with a 1/4" or 3/8" T-nut is my goto method for quickly prototyping a solution. Sanded and painted gloss black, it looks quite good.

Alright, thanks to everyone for an informative and productive discussion, but I feel like a bit of an idiot.

 

It seems as though there's an easy fix to my immediate problem...looks like I should be good to go with a replacement bushing.

 

 

 

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Jeez! I'd hate to meet the dog that chewed your monorail block Ben.

 

And a camera that size and weight really should use a 3/8" mounting screw.