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View Full Version : Threading a lens board hole...who does that?? :p



Mark Carstens
5-Jun-2010, 08:11
I'd like to thread a lens board hole but I'm no machinist. I know that SK Grimes would happily do it and charge me more than the board cost in the first place. Not my first choice.

So, my question...is there anyone within shouting distance of the SF Bay Area that does have the means and skill to get this done?

PM me if you have a contact.

THNX!
~Mark

Nathan Smith
5-Jun-2010, 08:26
Sorry, but do you really thread the lens board? Not saying that it's not done, but I haven't seen it. I may well be missing something.

I think that a more standard method is to have the machinist make a threaded retaining ring, and then the ring is screwed into the lens board.

SK Grimes does do that. I'm sure a good local machinist could do the same once they understand the requirements. Which is cheaper will depend on the machinist I suppose. If you can find a skilled amateur you'd probably do well to bribe him with whatever libations he prefers.

Mark Carstens
5-Jun-2010, 08:36
You're right, Nathan. Generally speaking you use a mounting flange or a retaining ring to attach lens to board.

In this instance, there isn't room for the custom mounting flange that was made for the lens by its previous owner (it's a rectangular cast aluminum plate with mounting holes near the corners). Threading the board is actually the most efficient use of space (it's a technika-style board...tiny) given that the lens is a 24" APO Artar in barrel.

In essence, it's as if I'm making the board and flange/ring an all-in-one proposition.

~Mark

RichardRitter
5-Jun-2010, 08:37
Yes it is done. I have done it in the pass. Not a good practice because you can not position the shutter controls in an easy to work with position. A flange or retaining ring is better.

Cost figure an hour plus of time to set up the lathe and do the work.

Mark Carstens
5-Jun-2010, 08:43
Thanks, Richard! I agree. I think our posts passed each other on the way to the site. :)

I've noted the limitations I'm working with in post #3.

I'll be making a front-mount Packard shutter attachment, I just need to get the barrel on a smaller "universal" board so I can use it with both of my cameras. I have the board already. It's bored out to 76mm and the barrel threads are in the neighborhood 77-78mm.

~Mark

Nathan Smith
5-Jun-2010, 08:45
Ok Mark, that makes sense. Sorry for the lecture :)

You know, we need to find a retired machinist and let him know how easy it would be to make good pocket money doing little projects like this. Not to take anything away from SK Grimes, but I'm sure there are plenty of us with projects and tight budgets that would love an alternative.

PS - I'm falling behind in this conversation, I obviously type too slowly ...
Richard, I'm glad to hear you do this sort of thing! Just found your website too: http://www.lg4mat.net/

Thanks!

RichardRitter
5-Jun-2010, 08:48
You're right, Nathan. Generally speaking you use a mounting flange or a retaining ring to attach lens to board.

In this instance, there isn't room for the custom mounting flange that was made for the lens by its previous owner (it's a rectangular cast aluminum plate with mounting holes near the corners). Threading the board is actually the most efficient use of space (it's a technika-style board...tiny) given that the lens is a 24" APO Artar in barrel.

In essence, it's as if I'm making the board and flange/ring an all-in-one proposition.

~Mark

You are talking about a custom made board. A Linhof Tech style board is to thin for the minimum amount of threads you need to hold the lens.

vinny
5-Jun-2010, 08:54
Mark, I've done a similar thing using linhof sized boards made of ABS, you have to drill a hole very close to the lens size and then just screw the lens in. Threading a metal one wouldn't work well unless it was thick aluminum like the generic boards you find on ebay.

Mark Carstens
5-Jun-2010, 09:23
Hey, Vinny!

You and your ABS...everything. :p

I have a Toyo-made board, and my first impulse was to try and thread it on, but I think the opening is just a bit too small. That, and I was concerned about mucking up the threads on the barrel.

~Mark

BrianShaw
5-Jun-2010, 09:33
...but I'm sure there are plenty of us with projects and tight budgets that would love an alternative.

In my experience, the words 'tight budget' and 'custom machine work' don't belong in the same conversation. Custom machine work is expenseive becuase of its very nature, as Ritter points out.

To this conversation I'd add, "small plating job" as something that just can't be done affordably!

Folks on a budget, like me, generally need to seek an alternative approach... and mostly one that can be done by oneself.

Bob Salomon
5-Jun-2010, 09:37
Terry Shuchat does.

Mark Carstens
5-Jun-2010, 10:28
It's hard to argue your point, Brian. "Tight budget" and "custom" anything are generally mutually exclusive.

But with that said, it never ceases to amaze me the conversations and ingenuity that surface when these kinds of questions are posed. Useful stuff much of the time.

~Mark

RichardRitter
5-Jun-2010, 12:04
In my experience, the words 'tight budget' and 'custom machine work' don't belong in the same conversation. Custom machine work is expenseive becuase of its very nature, as Ritter points out.

To this conversation I'd add, "small plating job" as something that just can't be done affordably!

Folks on a budget, like me, generally need to seek an alternative approach... and mostly one that can be done by oneself.

Yes I had a lens come in for work that was soldered onto the lens board. How to mess up a very expenses lens.

BrianShaw
5-Jun-2010, 12:50
But with that said, it never ceases to amaze me the conversations and ingenuity that surface when these kinds of questions are posed. Useful stuff much of the time.

Agreed. That's why I stick around this site so much!

Hey... here's a piece of good advice I read somewhere on the internet: Don't solder your lens to the board. :D

BrianShaw
5-Jun-2010, 12:53
... and I suppose epoxy would be an equally bad idea. ;)

Mark Carstens
5-Jun-2010, 12:56
... and I suppose epoxy would be an equally bad idea. ;)

Oh...it is?

I'll guess I'll stop looking for that tube of Super Glue then too. :p

Struan Gray
5-Jun-2010, 14:12
I squeezed a 18" Apo-Lustrar onto a Linhof board by using a standard flange and tapping the holes for the retaining bolts (M3) rather than using a nut on the back. That was a lens with a 72 mm mounting thread, so the flange fit inside the circular light trap. I had to do some work with a needle file to shape the ends of the bolts as they ended up emerging through the light trap metal. I also had to file off the sides of the flange so that they did not overhang the edges of the board or foul the lensboard attachment points.

With a 77-ish mm lens thread any flange is probably going to interfere with the light trap. My preferred solution would be to make a conventional flange whose rear protrusion is the correct diameter and depth so that it forms the light trap. Then bore out the lensboard just wider than the trap and mount as above. If you don't like just the tapped aluminium holding the lens on, you can always glue the flange onto the front of the board for safety.

Harold_4074
7-Jun-2010, 17:41
Having done a few of these exotic mountings myself, I suspect that in your situation I would have a machinist convert the existing, threaded board into a retaining ring, and then make an appropriate opening in the new board to accept the ring. The barrel threads are almost certainly metric, and relatively few inexpensive (i.e., small) machine shops are fully equipped with metric equipment. You can usually get away with the nearest English thread, but this is only because there are so few threads engaged---not the best occasion to fudge the dimensions!

To thread your replacement board, the machinist would probably wind up boring a test thread before doing the actual part, thereby at least doubling the scope of the job. Cutting down the threaded board, however, would only require a simple spud and clamping disk, both of which are simple and usually made from scrap.

For assembly, you could put slots or pin holes in a (narrow) flange on the inside, or, for really minimal interference, treat the threaded ring as an insert and just epoxy it in place. The deluxe version of this would involve matching tapers on the ring and lensboard (the ring barrel then its own flange, so to speak) but this is probably overkill. If you decide to do the glue thing, first orient the shutter and mark the parts, so that the controls will end up where you want them.

Harold_4074
7-Jun-2010, 17:44
Oops---I was visualizing the last time I did something like this; you did say that it was a barrel lens, so it is the aperture index and not the shutter controls that you want to position gracefully......

Mark Carstens
7-Jun-2010, 18:50
I have a "flange" for the lens.

It's a cast aluminum beauty that only a mother could love.

Check out the pics. The flange with ~77mm threads and the lens board with a ~76mm hole.

And, yes, the flange is too big to mount on the back of the board as-is. It extends beyond the edges of the lens board or I'd just enlarge the hole and I'd be golden. The flange could be cut or ground down, I suppose, but not by me. I don't have the proper tools.

BTW, thanks for all the suggestions!!! :)
~Mark

Struan Gray
8-Jun-2010, 00:02
Cut the corners off the 'flange', and cut/file down two of the sides so that it doesn't foul the lensboard locking latches. Then glue it to the front of the board. For extra security, drill four holes on the diagonals and thread them with a hand tap - fasten with a countersunk bolt (one with a bevelled head) from the back and dab black paint on anything shiny.

Hacksaw, file, drill and hand-tap are the only tools you need. The only tricky bit is deciding which of the four sides will be 'up': when I've done similar things I've screwed the lens into the 'flange' and played with it on the lensboard to see which of the four options is least bad.

Mark Carstens
8-Jun-2010, 06:03
Thanks for the suggestions, guys. I especially like the ones you offered Struan. Having the hole widened and a new flange made would be ideal, but I think I'll try working a little magic on the old "flange" first.

Thanks, too, for the reminder about avoiding the light trap on the back of the board.

~Mark

Mark Carstens
13-Jun-2010, 21:32
Macgyver is in the house!

I cut down two sides of the flange; just enough so that it would clear the top slider and bottom slot of the Technika adapter board. I backed the flange with a vulcanized rubber sheet (with a hole in it, of course), and glued same to the Technika board. It formed a kind of flange/board sandwich.

NOTE: If you try this yourself, the glue needs to cure overnight; (I removed the lens after taking the snaps I've attached). If you screw your lens onto the thread before the clue cures, you may end up bonding flange to lens and not be able to remove it later.

Speaking of glue...I used Elmer's "Ultimate Glue" which I've used before (on the same flange/lens combo and an Arca Swiss board). It forms a semi-permanent bond, i.e., it holds unless you really work to overcome it (that's what the rubber gasket is for -- that and to provide about 1/16" (~2mm) relief between the lens board and the flange so the Technika board didn't hang up on either the top slider or bottom slot of the adapter board.

Thanks again to all who offered ideas!

Next on the project to-do list...attaching a Packard Shutter to a front-mounted board so I can actually use the lens. :p

~Mark