How to center ext. thread to int. thread? - Page 2
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  1. #21
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    Quote Originally Posted by Mechanola View Post
    Can the air be taken out with lead foil? I am seeking the right material for a temporary use.
    Teflon tape?

    Fighting the wrong part of the problem if no option for re-design at-source.

    Lock it down.

    Rotate the environment around it on truly PRECISE bearings.

    I'm serious. Not as if it was a main-battery turret on an Iowa class warship.

    Total mass is trivial. Overall size not that big of a deal.

    Scale your MIND up.

    Rotate the whole box, ... or a first-surface mirror...rather than dig tiny holes down inside of it.

  2. #22
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    Gotcha. Guess why I placed the subject under metrology, it’s a set-up thing to me as with checking something like cylindricity or flatness.

    Cameras and lenses are given. I want to be able to have a C-mount lens (A and B mounts were known with the early Filmo 70s and Victors in the 1920s) centered in the turret port to be able to adjust everything. Professional lens mounts such as the PL bayonet retain an directional error of up to 0,06 mm (Ī 0,03 mm or Ī 0.0011"). I find it ridiculous since most any lathe three-jaw chuck is centered on the spindle by the short taper mount within half a thou hands down.

    Shouldn’t it be possible to have titles and every shot centered on the film? The crucial point is repeatability. Remove a lens, attach it back, you have a too large error in that.

    I’ll continue experimenting.

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  4. #23
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    I'm having a hard time visualizing, but what about a plastic sleeve that aligns the OD of the lens and the base? The threads won't do any aligning, they just hold the things together.

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    An idea. If I understand you, I should hold a lens in a plastic part having a tight fitting female thread, bring both into the desired position, and finally compare that to the lens ports of the camera. Not bad, I must say. Would need a compound of slides with clocks in order to measure out deviations.

    Still all lenses donít have the same threads meaning Iíd have to cut a fitting thread for each and every lens, if I donít use some kind of a threaded collet. That seems too much effort, Iíd prefer to have a quick and reliable and cheap solution for my clients as well as for myself. Itís just about evenly filling the varying space between an internal and an external thread.

  6. #25
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    It might be an overly simple solution but, could you orient the camera so the lenses pointed down or up so gravity would pull them into alignment?

    Edit: I see this isn't just a personal project.

    Edit 2: Would there be room to add lock nut you could tighten by hand to draw the slop out of the threads?

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    Kenton, no alterations can be made to lens threads or to camera ports. And no, there’s no room for a lock nut.

    I did imagine a solution that’s based on three thin slots cut through a sacrificial turret disc where I would install three music wires to elastically act on the crest of a lens’ thread but it wouldn’t be a solution to the actual camera in question. It’s really about adjusting particular equipment in itself so that I can give a customer the certainty he deserves. Else a critical focusing system is pointless and one better picks a camera with a reflex finder. To round this off, reflex finders have their own share of imperfections. Above all they are rather costly at maintenance.

  8. #27
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    No idea how it looks but if there is a cilindrical part on both sides of the joint you could use a spacer fitting these cilindrical parts
    Some pictures would be nice

    Peter

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    Quote Originally Posted by Mr_CNC_guy View Post
    Could you use an expanding 5C collet? Cut the correct thread in the
    expanding part of the collet.
    This is the way to go

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    I have found a source of rolled lead. They got foils of 0,02 mm thickness, around 8 tenths. Think that will lead further.

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  12. #30
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    Quote Originally Posted by Peter from Holland View Post
    No idea how it looks but if there is a cilindrical part on both sides of the joint you could use a spacer fitting these cilindrical parts
    That is the case with Bell & Howell Filmo 70 mounts A and B. With a Victor model 5 I have found that the lens portsí cylindrical mouth isnít round but slightly polygonal non circular, in three directions. You donít see it by the naked eye but it can be measured. The C mount in use since around 1930 consists of two threads, no more. Bell & Howell had noticed that only a vanishingly small number of camera owners would use the precision of a cylindric fit. Therefore they felt free to simplify matters. Whether a title will appear well centered on screen actually nobody cares about. What an uneducated world!

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    Would plumbers PTFE tape work?

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    Quote Originally Posted by Mechanola View Post

    It’s about optics. I have a lens and a camera with a turret, say a Victor, a Bell & Howell Filmo 70, a Paillard-Bolex H, an ETM P. These have critical focusing aids built in. The camera is mounted on a rack-over device, Bell & Howell called their accessory Focusing alignment gauge. A lens is turned to the position in front of the focuser, the camera slid to the side. Now I can frame and focus. Next I turn the turret plate to take the lens before the exposure aperture and move the camera to the other side of the rackover support (same distance as lies between two turret ports). The lens occupies the position it had when I framed and focused.
    This is so confusing that it makes my head spin.
    As I get it this is about alignment and not shouldered so kiss that datum goodbye.
    I could see where leafs help but are not real reliable as by definition soft and move since they do not like the high spots.
    Pictures of what is being done and the error concern ?
    Bob

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    Yeah, sure, as soon as I got the socket together that will hold the rack-over support with the camera on it. Socket in vice, a target one meter in front of it, will be my optical bench. Hereís an image of an 8mm camera on the rack-across support. Behind the upper turret port is a prism that has a depolished front surface equally deep in the camera as the film runs behind the middle opening. Through the eyecup you can observe the image on the prism face, magnified two-and-a-half times.

    h-8-auf-rackover-hugo-meyer.jpg

    frontgruppe-frisch-abgenommen.jpg

    This image shows the freshly removed front assembly of e ETM-P 16. Again the exposure aperture and a ground surface for accurate focusing behind the right-hand side lens port of the turret (seen from behind camera towards scene). The ETM has a retractable periscope (hence the P) for a magnified view of the ground glass.

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    In my original reply I was unaware this was for cameras.

    Could you make a collar for the camera and mating sleeves for the lenses that use a short taper for alignment? IMO it is impossible to make removable threads mate consistently when taken apart and reassembled without some other means of registration.

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    At some point of time I wanted to attack the camera lens ports, give them a short taper. Lenses would get a round wire behind the thread so that there is a fit between a cylinder and cone with the round body in between. Unfortunately, camera threads often have little flesh around the thread.

    The engineers with the Bell & Howell Co. had decided to licence out the story to A. F. Victor who could boast a first in his model 3 in May, 1928. No evidence or proof, but the Filmo 70 lost the B mount some day before 1929. As if they had known what will happen in autumn! A number of licencees paying quarterly or half-annually kept B. & H. more or less afloat through the depression. Interesting part of American history and of Chicago!

    The next bigger packages sold by B. & H. went to Facin Co. in France and to Paillard & Cie in this country, who both presented brand new narrow-gauge cameras in 1935. The Facine was available for Pathť 9.5 mm film and 16 mm from the start, a single lens port. The Paillard H cameras came with a cut-off three lenses turret. During the early years the B mount was used. Itís confusing until the corresponding utility or model patent is found.

    Zeiss-Ikon proposed the Movikon 16 in 1932. Initially there was a tapped lens port, later a proprietary lens bayonet.

    Iíll be back.

  18. #36
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    what i do sometimes is to electroless nickel plate stuff. very uniform layer. easy. but your threads probably have some coating already.


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