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m42 adapter modification

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    Posted: 03 May 2006 at 11:32
Hi all,

It seems all the adapter design is a copy of one another.
what bugs me is the thigtness issue when mount-unmounting them. So, I make comparison between 2 adapters and standard min.af mount.

Here is crude schematics


Overall lens mount plate (flange) diameter (not lens tube) of km(17-35,35-70) and tamron 90 is 62mm; both adapters is 64mm. Maybe this 2mm diameter differences designed to facilitate extraction by grabbing, or old design based on minolta slr, don't know for sure.

Notice the blue box in above schem. (which min.af lenses don't have). That part is 1mm outermost diameter of the adapter, the thickness (height) at (A) is actually not level with flange on camera, hence the protrusion.

Ignore B, it's the highest thickness in C which important, must not exceed 1mm, but I can't meassured it with my cheap plastic caliper.

In my adapter copies, thickness at A (blue box, 1mm outermost part) is varied between 1,3 to 1,5mm. When mounted on camera, due to the thickness, this part is 'enveloping' camera flange. The problem is, it's also pressing and make friction with camera body surface just outside the mount; maybe also affect infinity focus on some adapter. I hope there is no other side effect to lens mount precision.

I think that part is unnecessary, or part of bad design. Too bad I don't have right tools to level out or cut that part :(

Anybody willing to try modifying their adapter?
Please share your obsevation... especially adapter thickness at C and A (blue box, 1mm outermost part)
 



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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 04 May 2006 at 14:08
OK, I did it...

I'm reducing the thickness from outermost 1mm on both of my adapter. Now I can mount-unmount both of them (m42 lens attached) as easy as standard min.af lenses, no more pressing and friction to camera body. In one adapter it seems also improving focus at infinity, not reach the ~ focus yet, but better than previous (still too thick along C, another issue).

It's a crude job, I'm doing it with sandpaper :(, but better the adapter who suffer than my 7D.

Now I have adapter with gold ring, 'G' series adapter , LOL

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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2006 at 00:23
update...

Obviously one of my adapter is too thick along C, so lens attached to it can't achieve infinity focus. I have reduce the thickness of that adapter, sanding the adapter surface at the side facing the lens.

It's ugly but works, now lens attached to it can focus at infinity.
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Post Options Post Options   Quote Bob J Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2006 at 11:05
The measurements of my adapter (ordered from Hong Kong via ebay) are as follows (the measurements were taken at each bayonet the range shows the variance from smallest to widest measured):

A: 1.55 - 1.59mm
B: 1.94 - 1.97mm

I also measured the hight of the step from the raised part at A to the floor a C - this came to 0.49mm - I can't get an accurate measurement of the small step down in the middle of C with the electronic caliper I have, but reckon it it in the region of 0.05mm...

This gives a depth of C (measured where it meets A)of between 1.06 and 1.1mm.

BTW, I also measured the distance between the elevations at B and A (corresponding to your orange line), which came out between 6.43 and 6.45mm. the overall depth of my adapter (measured from the front plate to the back of the bayonet is 5.9mm

I've not tested this adapter with M42 glass to see if it will focus to infinity.

Bob
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 06 May 2006 at 14:34
Originally posted by BobJanesSE2 BobJanesSE2 wrote:


The measurements of my adapter are as follows ... :
A: 1.55 - 1.59mm
B: 1.94 - 1.97mm

Similar like my HongKong adapter, for comparison, my unmodified old Hama is around 1,3mm at A and 1,85-1,9mm at B.
For HK adapter I'm reducing the thickness at A and B. For Hama only at A.
Now both adapter measurement at A is around 1mm and 1,8-1,9mm at B.

Originally posted by BobJanesSE2 BobJanesSE2 wrote:


This gives a depth of C (measured where it meets A)of between 1.06 and 1.1mm.

According to mount register data at http://www.a1.nl/phomepag/markerink/mounts.htm thickness of m42 to min.af adapter (at this point) must not exceed 1mm. I don't know the tolerance treshold, but it's better be slightly thinner than thicker.

Originally posted by BobJanesSE2 BobJanesSE2 wrote:


The overall depth of my adapter (measured from the front plate to the back of the bayonet is 5.9mm
I've not tested this adapter with M42 glass to see if it will focus to infinity.

My unmod.hama and mod.HK is 5,75mm.

Thanks for your input Bob.       
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Post Options Post Options   Quote Bob J Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2006 at 01:22
Always trust in the skills of other family members.

My father (retired instrument maker) pointed out that the way to assess the diference in register between the Minolta mount and the Hong Kong mount is to attach the adapter, rotate it so that it is just short of latching and then measure the depth of the hole in the adapter (which goes right through from one point of register to the other). This method of measurement gives a diference of 1.19mm (so an M42 lens will not focus to infinity with this adapter!)

My wife (proof reader) also contributed by pointing out that I had failed to close my brackets in the bit of text quoted above...

So the next question is - what would be the best way of taking 0.19mm off the face of the adapter?

Bob
 



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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2006 at 01:31
Originally posted by BobJanesSE2 BobJanesSE2 wrote:


So the next question is - what would be the best way of taking 0.19mm off the face of the adapter?
Bob

this is what i've done:

-'hack' inclined:
sanding down adapter face, using flatened sandpaper on level surface, adapter on top of sandpaper with gentle equally pressured rotating movement, also rotate the adapter orientation every 30 stroke or so.

-'socially' inclined:
i've 'persuade' the adapter maker to redesign the adapter using my measurement :D he's already working on it, but still have to wait for the new version though.

it's obvious that i aim for cheap solution :)     
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Post Options Post Options   Quote Bob J Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2006 at 01:40
Nur,

How long does it take to reduce by 0.19mm by the sandpaper (emery?) method?

Bob
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2006 at 02:00
hmmm...

under 1 hour, i go slowly and hesitant at first :)
it includes several cycle of sanding, washing, and test, as i don't really know how far i should go; can't relly on my cheap plastic caliper :)

i just comparing pics on computer at 100%, and repeat as necessary. HK adapter is quite soft & i've done it at lunch hour :D

and don't forget to rotate the adapter on your grip periodicaly, as our finger don't give equal pressure.

should be easy for you (and you have reliable caliper) :)

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Post Options Post Options   Quote TheHollowMen Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2006 at 09:41
When the adaptor maker creates a new adaptor, can you give us a yell? I'm sitting here tense as I have a suitcase of old screw mount lenses and am wanting to order a few adapters
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2006 at 11:02
will do,
already ask him about it, will report here when it's available and pass the test.
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Post Options Post Options   Quote kiklop Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2006 at 11:30
Well, if this new modified adapter will work fine then I'm ready to support it here on dyxum with free advertising :)
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Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2006 at 13:54
thanks Kiklop,
i'm sure it would be a very good support. i've quoted your post and forwarded it to him. i'm sure producing / modificating it can be done -cheap- in HK.
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Post Options Post Options   Quote kiklop Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2006 at 14:10
No problem at all.
Dyxum will always support those who are helping our community.
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