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04-06-2017, 06:22 PM   #16
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QuoteOriginally posted by MarkJerling Quote
I'll stick to my knitting.
Making cameras is more fun for me.
Here is my attempt to make a mount for a medium format Graflock using 70+ year old vintage measuring equipment.
https://app.box.com/s/eudh2q4yvz2j60l4tbx19607rbecewqv
In those days, Rochester USA was the photographic center.
There was a USA standard that stipulated the allowable film flatness tolerances on these press type camera backs, which was a warp limit of 0.007 inch (0.178mm)

When I adapted a Super Angulon 65mm to a 1953 Baby Graflex, I had problems with tolerance on the front standard with that wide angle lens.
So I made a "jigger" milled flat and square, to set up the camera. It was a challenge to get it right.
https://app.box.com/s/f4mx4n06jpveooq6fksud3i8yv98hlea
I learned on APUG that such "jiggers" were somewhat common back in the day to align non standard lenses to the old cameras

04-06-2017, 06:49 PM   #17
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QuoteOriginally posted by dcshooter Quote
Probably not that much of an issue,tough, since there is typically enough extra play at the end of the helical that it can be adjusted +/- 1mm or more. LEt's face it, if you are brave enough to take a mount off, it's just a tiny bit more of a step to adjust infinity. I'd be much more concerned about tightness/wobble.
Yes, a tolerance can be "tolerated" if the mount faces are parallel with low error.
The problem on the old Graflex was that of slight skew ( the lens axis was not at 90 degrees to film plane.) even when i tried to adjust the stops.
So my photos were blurred on one side. Especially when opened up to f/8 !
https://app.box.com/s/38xrkjzk0j97d65i2erakjb03vqf6sz6

I think I have it squared up now, but have yet to do a few rolls to prove it.
04-06-2017, 07:05 PM   #18
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QuoteOriginally posted by MarkJerling Quote
I understand some of the latest machines will give accuracy of 0.05mm. But, costs for using those are likely to be higher. I know someone with a DMLS machine - I must check with him what his tolerances are. I know he can print up to 245x245x280mm maximum size, but I'm not sure of the tolerances.
I've checked. I can confirm 0.05mm (50 microns) is the accuracy now possible.
04-06-2017, 07:12 PM   #19
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QuoteOriginally posted by MarkJerling Quote
I've checked. I can confirm 0.05mm (50 microns) is the accuracy now possible.
Assuming the object is a basic puk, is that tolerance the error between pieces, or in the volume of one piece?
Thanks

04-06-2017, 07:30 PM   #20
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QuoteOriginally posted by MarkJerling Quote
3-D printing in titanium is available with accuracy of 0.2mm and surface roughness of 0.075mm. Provided you uploaded the 3-d file then the cost would only be around $70-100 per mount.
Of course, that may not be a tight enough tolerance. Not sure. Based upon the original K-mount drawings posted here - Looking for K mount blueprints/technical drawings - PentaxForums.com - that accuracy may be enough.
You mean the Russian language drawings? Those are Soviet GOST specs for KMZ (Zenit) K-mount lenses and bodies. The fit on a K-mount Zenitar is not bad (I have one of their products in K-mount), but not as good as genuine Pentax or Japanese-made 3rd party.

Your comment regarding tolerances is well-made. The body side tangs are spring-loaded to allow for some variance.


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04-06-2017, 07:33 PM   #21
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QuoteOriginally posted by wombat2go Quote
The classical thin lens function:
(1/f) = (1/v) + 1/u)
units [mm]
where f : focal length = 50mm for example
u = distance from n2 to film plane
v = distance from n2 to the subject being photographed

Case 1 : Adaptor Error = zero, subject : 100 metre = 100000 mm
(1/50) = (1/100000) + 1/u) > u=50.025mm

Case 2 : u = 50.025 mm from case 1. Adaptor Error = 0.2mm, subject : to be calculated as v
(1/50) = (1/v) + 1/50.025) > v = 11161 mm; v= 11.161 metre`
You have a classic thin lens in K-mount


Steve
04-06-2017, 07:46 PM   #22
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QuoteOriginally posted by stevebrot Quote
You have a classic thin lens in K-mount


Steve
I think I do , and added bonus is a thin plastic lens!
Thanks to Jean and his crazy projector lens club!
But it is in the attic and the photos of it/by it are I dunno where. Let me look.

(Anyway for this purpose that calculation is OK for any 50mm K lens.)

Edit: After many searches , found it!

https://www.pentaxforums.com/forums/122-lens-clubs/264161-projector-lens-clu...ml#post2888731

Last edited by wombat2go; 04-06-2017 at 08:06 PM.
04-06-2017, 08:59 PM   #23
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QuoteOriginally posted by wombat2go Quote
Assuming the object is a basic puk, is that tolerance the error between pieces, or in the volume of one piece?
Thanks
As I understand it, that's variance from any given point per the 3D CAD model to the manufactured product.

04-06-2017, 09:50 PM   #24
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Structural integrity aside, how do you intend to fit the mount with appropriate lens data communication contacts?

QuoteOriginally posted by MarkJerling Quote
3-D printing in titanium is available with accuracy of 0.2mm and surface roughness of 0.075mm.
QuoteOriginally posted by dcshooter Quote
0.2mm isn't a tight enough tolerance to ensure that things won't bind and that things like the locking pin will line up.
DCshooter, you're right and with a material like titanium seizing will be more problematic and will be compounded by lax tolerances. With alloys that self-generate an oxide surface film for corrosion protection: During tightening, as pressure builds between the contacting and sliding surfaces, protective oxides are broken, possibly wiped off, and interface metal points can shear or lock together. This cumulative clogging-shearing-locking action causes increasing adhesion. In the extreme, surface damage can lead to seizing - the actual freezing together of the surfaces. Using graphite as a lubricant can prevent this issue, however it needs to be applied carefully across the contact surface.

Last edited by Digitalis; 04-06-2017 at 10:05 PM.
04-07-2017, 07:00 AM   #25
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QuoteOriginally posted by dcshooter Quote
Each step in this process would increase the cost of the conversion substantially, and really, I don't see anything beyond the Leitax style plus perhaps a stop down lever as remotely feasible outside of an industrial setting.
I agree, which makes the conversion mount not all that different from a common M42 screwmount adapter.
04-07-2017, 09:34 AM   #26
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although it is all the rage these days, is it really worth it. after all you can buy flanged M42 to K mount adaptors on Ebay for about $5.00 these days, and all you need in addition is shims the correct thickness to set infinity focus correctly.

what does it cost these days for a 3 d print. surely more than $5
04-07-2017, 01:57 PM   #27
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QuoteOriginally posted by Digitalis Quote
.... with a material like titanium seizing will be more problematic....
Can do 316 stainless steel too.
04-07-2017, 02:44 PM   #28
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They can do brass too, but not with the same accuracy as with titanium or stainless. The reason is that the brass process requires a secondary process - a lost wax casting.
04-08-2017, 12:36 PM   #29
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I still think it is not worst the effort, but what about replacement aperture l vers, for all the ones hacked off by canon uses
04-08-2017, 12:45 PM   #30
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btw. if anyone wants really high quality lens elements for projects, i stumbled upon this:

Olympus Zuiko Digital 50-200mm f2.8-3.5.
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