Re: [Cameramakers] Cheapo Helicoid' focuser
Thanks; it always looked so formidable that I was frightened off. If it is hardly worse than a single start thread, it is well worth considering. I appreciate the encouragement, and still worry, but less! Bob At 21:03 24.02.02 -0500, you wrote: Re;Barry Young [EMAIL PROTECTED] The second time you do a multistart thread it is cake. You, Sir, also speak from knowledge. bye, sid. ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
Re: [Cameramakers] Re: Cheapo Helicoid' focuser
The only drawback that I can see to this is you cannot turn your lever past the dowels so your range of focus would be imited by this. Your thinking is quite correct. That's the reason for the multiple start threads- to multiply the linear travel with reduced angular rotation. Given a suitable MS thread, your dowel-guided system works nicely. Happy building, bye, sid. ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
Re: [Cameramakers] Cheapo Helicoid' focuser
Dear Barry, Perhaps you have some advice on getting the depth correct. The obvious solution is wires, for the outside thread (except for those who are lucky enough to have a thread micrometer.) How is the mating inside thread monitored for depth? This is the operation which was my worry when expressing concern. With a single start thread you can advance in small steps, using the outside thread as a gauge. With four starts that is a little trickier; you have to cut all four, test, and if more metal must be removed, repeat. Conversely, if one can measure, there is no big problem in advancing the tool the right amount. Unfortunately, I have never even seen a micrometer for inner threads! You advice will be welcomed by all who might have to face this problem. Bob At 15:22 24.02.02 -0800, you wrote: Hi Robert: Most multi start threads used in photographic equipment use three or four starts. All I have made as replacements have been 4 starts. This is easily indexed using a machined block under each of the jaws on the four jaw chuck. You can do it, only the first one is difficult. The second time you do a multistart thread it is cake. All the focusing helicals I have seen have 60 degree included angle thread flanks. Barry Young ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
[Cameramakers] copier lenses
the copier lenses I have seen have all been glass, mostly from 1980s surplus I'd bet. The plastic lenses you see are more from projection TV setups and should be avoided (soft..). the projection quality of 8 1/2 x 11 prints strongly suggests the copier lenses can make excellent 8x10; many of these lenses seem to also work to cover up to 11x17 on many copier machines. these lenses are used all the time as astro spotting scopes, at infinity; I don't know the infinity coverage, which probably varies with different lens types and formulae, but again, I'd be surprised if 8x10 was a problem on any of them. I'd also be surprised if the result wasn't at least as good as some of the older barrel lenses, esp. as some of them seem to be coated optics etc. on the other hand, there are lots of process lenses being thrown away every day as folks switch to digital... bobm * Robert Monaghan POB752182 Southern Methodist University, Dallas Tx 75275 * * Third Party 35mm Lenses: http://people.smu.edu/rmonagha/third/index.html * * Medium Format Cameras: http://people.smu.edu/rmonagha/mf/index.html * ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
[Cameramakers] re: focusing mounts
I'd point you towards some of the amateur telescope maker designs for eyepiece focusing designs. A lot of these are built around plumbers tubing and brass/copper pipe stuff. But they have a lot of simple focusing mount designs that might be a starting point?... hth bobm * Robert Monaghan POB752182 Southern Methodist University, Dallas Tx 75275 * * Third Party 35mm Lenses: http://people.smu.edu/rmonagha/third/index.html * * Medium Format Cameras: http://people.smu.edu/rmonagha/mf/index.html * ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
Re: [Cameramakers] Homebuilt lights
I'm not familiar with the Speedotron lights, but as long as the modeling light is inside a helical flash tube, there should be no real problem in adapting it to any stage lamp with enough room inside. bye, sid. ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
Re: [Cameramakers] Cheapo Helicoid' focuser
Hello Robert: Almost all internal thread pitch diameters are measured with thread plug gages. You make one a little big and one a little bit small. When the small one enters and the big one doesn't, Ta da! you are there. For thread form however, almost everybody uses the impre4ssion method. The truly cool use dental impressioning compound, You heat it with a lighter (preferably a Bic lighter) and it softens. When you press the softened impressioning compound into the thread, it cools and solidifies leaving a near exact replica of the thread. Dental compound is dimensionally stable meaning it is the same size when cool as when heated. Amazing stuff, but hard to find and spendy. I recommend the poor mans impression stick. If you have kids it is easy. Steal one of their crayons when they are asleep. If you don't have kids, steal one of those long tapered candles (tapers) the better half uses to lure you over dinner. If you are single, you can apply a light coating of spray on cooking non stick super slick gizmo stuff (Pam) and then fill a thread or three with epoxy. When it sets up, you have a good impression. There is no stealing for the single people though. The really cool thing to do is to slap that impression you made on your optical comparator. Lacking this, you can get at almost any part of the thread by sawing your impression on the band saw. Then you can just use calipers. BTW, since this IS a photographic group, you CAN (and I have) use an enlarger to project your threadform for easy measuring on the baseboard. Like a shadowgraph. I don't want to bore the people here to tears so drop me a line off list. Maybe I can give you even more ideas on where to steal essential shop equipment. Barry Young Ooops, I mean borrow! --- Robert Mueller [EMAIL PROTECTED] wrote: Dear Barry, Perhaps you have some advice on getting the depth correct. The obvious solution is wires, for the outside thread (except for those who are lucky enough to have a thread micrometer.) How is the mating inside thread monitored for depth? This is the operation which was my worry when expressing concern. With a single start thread you can advance in small steps, using the outside thread as a gauge. With four starts that is a little trickier; you have to cut all four, test, and if more metal must be removed, repeat. Conversely, if one can measure, there is no big problem in advancing the tool the right amount. Unfortunately, I have never even seen a micrometer for inner threads! You advice will be welcomed by all who might have to face this problem. Bob At 15:22 24.02.02 -0800, you wrote: Hi Robert: Most multi start threads used in photographic equipment use three or four starts. All I have made as replacements have been 4 starts. This is easily indexed using a machined block under each of the jaws on the four jaw chuck. You can do it, only the first one is difficult. The second time you do a multistart thread it is cake. All the focusing helicals I have seen have 60 degree included angle thread flanks. Barry Young ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers __ Do You Yahoo!? Yahoo! Sports - Coverage of the 2002 Olympic Games http://sports.yahoo.com ___ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
