[wombat2go]

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I took a close look at Not A Number's good photo.
There are some curly issues to making it in the lathe.

1. See how there are 4 thread crests with only a pitch of no-man's land groove to stop the tool at the end of the cut. That would require a specially ground tool to avoid clobbering the flange. -I suppose the production ones used the custom tooling of the lenses.
In my case, the threading tools are purchased from UK and expensive. So I would not be very happy to grind the end off a good tool just to do the job.

I have an old off brand M42 bellows here and the way that problem was handled, the groove was made wider so that there are only 2 crests. While it might have supported an slr, I would not be happy hanging a 800 gram dslr body on 2 threads.

2. About increasing the flange thickness. I think the castings are the same as the later Bellows -M which i have here. It only just gets infinity on the 100mm macro, and does not quite get infinity on a 90mm enlarger lens. So increasing the flange thickness might be a problem - not sure how much it could be increased.

The way I would make that here is to make the threaded adaptor piece with a spigot of about 38mm OD and press into a recess on the flange/bellows piece. That enables the thread to run right to the flange. It might be OK to trust Loc-tite to hold the 2 pieces, but I would use a grub screw too.

I still have the opinion that it would be better and easier to make a K mount adaptor for the old Ashai bellows, using a donor K-mount.

[Not a Number]

Would a 3rd party flanged M42 adapter work as a donor K-mount? I thought of using one of these instead of the OEM Pentax m42 adapter. There is some play no matter how tightly you screw in the bellows adapter. Not a big issue unless you are focus stacking.

FWIW I just acquired a Pentax Auto Bellows A with slide copier and will probably be selling my screw mount Auto Bellows.

[Not a Number]

I just had a thought (no comments from the peanut gallery!): You may be able to take an m42 extension tube and cut a groove in it for the set screw. This would already have the m42 male threads cut into and a collar to stop the tube from falling into the bellows.

Edit: ok, it won't work. The inside diameter of the tubes is 42mm, not the outside. But I suppose you could just slip a 42mm tube into the extension tube and cut the groove into the tube. You could epoxy or solder/weld them together.

[Ratmagiclady]

I've an original Auto Bellows and that flange. (I've just used it with a cheap-and-cheerful M42 extension tube to clear the prism housing and grip on my K20d, with a plain K-mount adapter (no worries about infinity focus: the kind from China that has infinity focus worries works fine for macro and seats nice and firmly. It's the kinds that try to preserve said infinity focus that you want the real mc coy for. ) it might be the body of the bellows that otherwise interferes rather than any other particular worries, but I actually forget by now. )

I don't know who may want to buy one, but I could conceivably loan that flange off for you to copy, if that would help. (Or possibly you could Ebay one with a bad bellows and get the flange that way, true.)

[MJSfoto1956]

there was a damaged bellows on eBay a few months back that went for about $10. I just missed bidding on it and have been waiting for another to show up with no luck. Will consider your offer of a "loaner" but am not in a hurry at present -- just feeling what others think. Thanks!

M

[Not a Number]

I wonder if the adapter ring from some of the other non-auto m42 bellows would fit? Pentax seemed to reuse lots of parts so maybe it is possible. There's a couple on ebay for under $25 right now.

---------- Post added 08-07-14 at 06:45 PM ----------

Here you go, all the donor mounts (both lens and camera side) that you want!

Job Lot of Asahi Pentax Lens Mount Rings SLR 35mm Digital Repair Parts New | eBay

[Ratmagiclady]

there was a damaged bellows on eBay a few months back that went for about $10. I just missed bidding on it and have been waiting for another to show up with no luck. Will consider your offer of a "loaner" but am not in a hurry at present -- just feeling what others think. Thanks!

M

Sounds good. (Heh, looking at your signature I wonder if you sold me my Canon F-1N on Ebay a good number of years ago. Still running good, if that was you. (In my bag now as a matter of fact. Had a little lubrication issue to work out in the frozen North but since then, all good. ) Or something. Think the name stuck out cause I'm from Boston and related to some Sullivans.

Heh, anyway, that'd be funny. I suppose I could at least verify visually if the mounting ring from a plain old M42 Auto Bellows is the same as what you need: they may be easier to come by in whatever condition.

(Mine does look to match Not A Number's example, though it has a black textured insert of some kind that I can't see on his photo. It doesnt' seem to change the dimensions of things though.

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Last edited by Ratmagiclady; 08-09-2014 at 12:33 PM.

[MJSfoto1956]

Sounds good. (Heh, looking at your signature I wonder if you sold me my Canon F-1N on Ebay a good number of years ago. Still running good, if that was you. (In my bag now as a matter of fact. Had a little lubrication issue to work out in the frozen North but since then, all good. ) Or something. Think the name stuck out cause I'm from Boston and related to some Sullivans.

Couldn't be me because my Canon FD system was stolen the first year I moved to Boston. Fortunately insurance paid for replacement cost and I then made the switch to Nikon F3.

Anyway, I do in fact have an earlier model Pentax M42 bellows but its "insert" is off by a few millimeters in diameter and thus cannot be used as a (low cost) source for such adapters. Still debating what to do. No rush.

Michael

[Ratmagiclady]

Couldn't be me because my Canon FD system was stolen the first year I moved to Boston. Fortunately insurance paid for replacement cost and I then made the switch to Nikon F3.

Ah, maybe we just talked about that. Or possibly it was was something else. I think my flash bracket came from Boston. (Ironically could use a little machining, come to think of it. I tend to remember things that came from home cause anyone'll tell you I get stupidly homesick. ) Pentax digital did attract a lot of longtime Canon FD holdouts. Most of my old-school Pentaxian cred comes from the 6x7. (So mean to me, made me look so good with results. )

Anyway, I do in fact have an earlier model Pentax M42 bellows but its "insert" is off by a few millimeters in diameter and thus cannot be used as a (low cost) source for such adapters. Still debating what to do. No rush.

Michael

Hrm. I actually don't know the cost of machining one for yourself, given you have the shop, apparently. Could you take a profile of the locking collar and then adjust said diameter on your lathe?

The thing about bellows is that even Spiratone used to make them awfully nice by present standards. I don't know if there's a huge market but maybe once in a while someone would be very glad to have the part or an extra, The old one I have is a beautiful no-frills-no-headaches basic piece of machinery that someone here gave me in part, if I recall, as part of an experiment to try and turn old bellows+duping frame+camera into a negative scanner that would work on crop sensors. (Result: 75mm enlarging lens seemed to work. Needed more light which I never did get hold of. Also I was going to mount the whole affair on a board for some reason I can't recall now. Possibly because the slide holder needed a longer stalk,which might *be* an interesting conversion part if you could make that.)

Also I got a kick out of using that bellows to adapt the K20d to a plate camera lens-shutter from like 1934 I've had since I was a teenager. (From Hong Kong you could get a reducer bushing to fit any M39 glass you please. In this case for like a 5x7 camera.