AO Cycloptic with bent shaft

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MichaelBrock
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AO Cycloptic with bent shaft

#1 Post by MichaelBrock » Fri Sep 07, 2018 7:56 pm

I picked up a very inexpensive Cycloptic type-M from ebay. It's in pristine condition except that the shaft for the focuser knobs is quite bent. On the theory that "what was bent can be un-bent' I removed it from the arm of the microscope. I'm left with one of the knobs attached to the shaft. Unfortunately, the diagram in the AO manual doesn't show detail of how it is connected. There is pin in one side of the knob and a matching hole on the opposite side. There is some play between the shaft and the knob (I can move the shaft side-to-side and in-out relative to the knob) so I don't think the shaft is threaded in like it was on the opposite end. I made a half-hearted attempt to push the pin out via the hole on the opposite side but it did not budge. Before i start banging on it in earnest, or drill it out, I wanted to see if there was anyone familiar with this "problem".
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MicroBob
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Re: AO Cycloptic with bent shaft

#2 Post by MicroBob » Fri Sep 07, 2018 8:33 pm

Hi Michael,
I don't know this specific microscope. But this pin is likely to be the only means of fixing the shaft to the knob. The pin will have a press fit in the shaft, squeezed together further by the bending of the shaft. I would try to kock this out to have better acess to straigten the shaft. Knock it out so the pin leaves the assembly towards you as imaged in the photo. It might need some force so think about it in advance and use proper tools. It is important that the shaft remains perfectly straight on the bearing surfaces left and right of the cog. So straighten it in a way that doesn't risk bending this area.

Bob

MichaelG.
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Re: AO Cycloptic with bent shaft

#3 Post by MichaelG. » Fri Sep 07, 2018 9:11 pm

Likewise, I don't know this specific microscope; but I woud add another word of caution
The pin might well be a taper pin, which will only remove in one direction.
... Bob is almost certainly correct about the direction, but it's safer to check the diameters if you can.

Standard Imperial taper pins have a diameter taper of 1:48

https://en.m.wikipedia.org/wiki/Taper_pin

MichaelG.
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MichaelBrock
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Re: AO Cycloptic with bent shaft

#4 Post by MichaelBrock » Fri Sep 07, 2018 10:03 pm

Thanks for the replies! The end in the pictures seems to be peened over a bit and I don't think it would fit through. Hard part is going to be setting it up to get a good solid backing...and finding something stiff enough to withstand the hammering (gentle).

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ebenbildmicroscopy
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Re: AO Cycloptic with bent shaft

#5 Post by ebenbildmicroscopy » Fri Sep 07, 2018 11:27 pm

You need a "drill block" to use as an anvil. I've improvised one once by buying a small galvanized pipe couple at Lowe's Home Improvement and used a triangle file to make a couple of v notches in one of the ends when you set the coupler on end like a soda can. The shaft will seat nicely in the v notches and the coupler provides a stout base for hammering out a taper pin.
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JeffO, aka "Ortho amore"
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ebenbildmicroscopy
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Re: AO Cycloptic with bent shaft

#6 Post by ebenbildmicroscopy » Fri Sep 07, 2018 11:32 pm

One other caution... that knob is made of bakelite which, while it is a wonderful and durable, even insulating material, IT IS EXTREMELY BRITTLE. Use a drive pin punch for knocking that pin out and make sure the punch is a little undersized in relation to the pin diameter. Bakelite is a phenolic material and does not like hammer blows.

Wishing you every success!
JeffO
JeffO, aka "Ortho amore"
Leitz Ortholux I
Leitz Orthoplan
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Zeiss GFL
Zeiss Standard
Zeiss Photomicroscope III
Zeiss OPMI 6S
B&L Stereozoom and Balplan

MichaelBrock
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Re: AO Cycloptic with bent shaft

#7 Post by MichaelBrock » Sat Sep 08, 2018 3:00 am

JeffO, thanks for the heads up! The collar where the pin is appears to be painted brass so at least that's sturdier. And thanks for the idea of using the drill collars to make a "drill block". I happen to have a pack of various sizes that I bought for some reason (whatever it was, it wasn't for their intended purpose).

MicroBob
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Re: AO Cycloptic with bent shaft

#8 Post by MicroBob » Sat Sep 08, 2018 6:56 am

My suggestion would be to take a board of the thickness of the lenght of the brass collar, drill a hole in it the size of the diameter of the collar, cut the board right through the hole and clamp the board in a vise/vice. Make a little room for the pin with a sawcut or two. Hold the assembly by the knob, the shaft touches nowhere and can't be bent thus.

The tapered pin remark is good, but I don't expect that they used a tapered pin here because service personnel would always get the direction wrong because it is so small and difficult to identify the taper. Anyway use caution in this regard. This will probably be a straight pin with some grooves in the middle to increase thickness here.
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MichaelBrock
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Re: AO Cycloptic with bent shaft

#9 Post by MichaelBrock » Sat Sep 08, 2018 5:59 pm

I asked this question on the Facebook American Optical Microscope group and a knowledgeable person there is warning me that these shafts are frequently bent...and frequently break when attempting to un-bend them. I will probably give it a shot but I may be back looking for a new shaft :)

Hobbyst46
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Re: AO Cycloptic with bent shaft

#10 Post by Hobbyst46 » Sat Sep 08, 2018 7:21 pm

If not for the hole on the other side of the knob, at 180 degrees from the pin "head", I would think that the shaft's last cm is not a perfectly cylindrical rod but is half-circular, shaped like a cam, and the knob is fixed to the shaft by means of a set screw that presses onto the flat side.

In cheap mechanical devices (not microscope parts - more like modern washing machines and ancient radio knobs) the knob has a matching "half-round" hole and is being forcibly pushed over and onto the matching cam end of the shaft.

Could that be the original connection here as well, until someone "improved" it by adding a tapered/non-tapered pin that passes through? that might perhaps explain the freedom of movement of the knob against the shaft. \it would also mean that the shaft is not bent... just cheeky fantasies :lol:

MicroBob
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Re: AO Cycloptic with bent shaft

#11 Post by MicroBob » Sat Sep 08, 2018 9:00 pm

If it breaks it would be possible to cut of the shaft, turn a recess and shrink or glue an extension on it. So if you know a friendly machinist, a repair might be quicker than searching for a parts donor microscope stand.

apochronaut
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Re: AO Cycloptic with bent shaft

#12 Post by apochronaut » Sun Sep 09, 2018 3:57 pm

I ended up with a Cycloptic that had a completely broken off knob but a good shaft, which I replaced with an entire part from a junker cycloptic. You can have my part , if you want; shaft and track. You could then drive out the pin on both and put your good focusing knob on mine.
I'm pretty sure those pins are peined slightly. To remove them, it might be a good idea to file the head off one side. I have a tiny drift punch that will do the job( I think. I haven't measured it or used it for that particular job). I will check and if it will work; I can include it in the package with the part.
Shipping that will jot be that expensive, probably around 10.00-12.00.
You can mail back the punch in an envelope , when you are done.

MichaelBrock
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Re: AO Cycloptic with bent shaft

#13 Post by MichaelBrock » Sun Sep 09, 2018 8:09 pm

Apochronaut, thanks for the offer! I'm gong to go ahead and give the de-pinning and unbending a try and if that fails I'll take you up on your offer.

apochronaut
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Re: AO Cycloptic with bent shaft

#14 Post by apochronaut » Sun Sep 09, 2018 11:32 pm

I have straightened about 10 AO pinion shafts....most of them the thinner versions on horseshoe based microscopes and one or two cycloptics and stereostars. They get knocked off of tables.

In each case I used very small amounts of force in increments. After each stage i would rotate the spindle to determine if that amount of force was enough to make a change, increasing or maintaining the amount based on that. Too much will definitely cause the metal to begin to cleave. Minimum , then rest, then minimum etc. etc. It worked in all cases.
Your bend is worse then any I have done. Mine were more of a wobble. It will be interesting to see how it goes. Good luck with that.

MicroBob
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Re: AO Cycloptic with bent shaft

#15 Post by MicroBob » Mon Sep 10, 2018 12:13 am

In a quality microscope it is to be expected that the steel of the shaft is heat treated to a medium hard condition. This makes a break more likely to occur.Steel is a material that generally prefers to be moved in warm condition. So it could be an idea to remove the pin and both knobs in cold condition and then do the bending after heating to a red color with a propane torch. The heat would remove the tempering and make it easier to bend the shaft.

MichaelBrock
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Re: AO Cycloptic with bent shaft

#16 Post by MichaelBrock » Mon Sep 10, 2018 4:41 pm

Try as I might, I was not able to remove the pin with the force I was comfortable in applying. I tried with Microbob's suggested jig but ended up splitting the first one (grain the wrong way) and just putting quite a dent in the second one. What I did discover in the process though is that the shaft is not actually bent at all! The brass collar which holds the pin is apparently a fairly lose fit. I found that I could simply push the knob against the direction of where the bend seemed to be and the shaft shifted inside the collar. I think it is simply pivoting around the pin. I managed to get it quite well aligned. It is maybe a little looser than it should be though and I suspect it will easily get knocked out again.

Thanks again for all of the advice and I apologize that I was unable to bring much of it to bear Hobbyst46 did suggest the possibility that the shaft wasn't actually bent!


I'm enjoying using the Cycloptic. The depth of field isn't quite as good as I was expecting of a stereo microscope (it's my first one) but it is definitely quicker and easier to use for opaque objects (namely sand) and of course the only option for anything of any thickness. Now I'm keeping an eye out for a 2x auxiliary lens.

MichaelG.
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Re: AO Cycloptic with bent shaft

#17 Post by MichaelG. » Mon Sep 10, 2018 5:28 pm

All's well that ends well

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Hobbyst46
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Re: AO Cycloptic with bent shaft

#18 Post by Hobbyst46 » Mon Sep 10, 2018 5:38 pm

MichaelG. wrote:All's well that ends well

MichaelG.
Likewise.

MicroBob
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Re: AO Cycloptic with bent shaft

#19 Post by MicroBob » Mon Sep 10, 2018 6:04 pm

No repair is better than a part thar needs no repair!
May be you can fill the gap with epoxy to keep the knop in the right position.

apochronaut
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Re: AO Cycloptic with bent shaft

#20 Post by apochronaut » Mon Sep 10, 2018 6:52 pm

Very good. one thing, I couldn't determine is; how did you get the shaft out of it's housing? You must have removed the other knob, somehow.

MichaelBrock
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Re: AO Cycloptic with bent shaft

#21 Post by MichaelBrock » Mon Sep 10, 2018 11:53 pm

apochronaut wrote:Very good. one thing, I couldn't determine is; how did you get the shaft out of it's housing? You must have removed the other knob, somehow.
The other knob just screwed off. The AO exploded diagram for the Cycloptic shows that end threaded and there was no pin. I held the pinned end and unscrewed the other knob. I figured it made sense since it is the process of screwing them in/out to adjust the focus tension (and as it turns out, keeping the entire head from simply sliding down...I may have cleaned and lubricated too well).

apochronaut
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Re: AO Cycloptic with bent shaft

#22 Post by apochronaut » Tue Sep 11, 2018 11:08 am

I think that is how the one I have got broken. After a few years the threaded side can get super tight and resorting to vice grips or other methods isn't going to be kind kind to the old bakelite.

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