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Silver steel or stainless?

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Chris R 125/01/2019 01:39:15
29 forum posts
18 photos

I'm not that confident the tailstock on the lathe will be very near the axis...

 

ANyway you asked for pictures:

This is the bit of microscope, the one existing rod is in place, screwed in a the point arrowed. It IS steel of some sort that it goes into. As you can see the rod goes through a large hole. Quite why they break I don't know.

rod.jpg

It's moving a filter cube in the fluorescence illumination head of a 'scope. There are two filters and a dichroic mirror in the cube. You use light of wavelength X, which reflects through the objective lens onto the subject, which you preload with fluorophores which emit at a different wavelength Y. None of X gets up the eyepiece / camera, so you only see your excited bit of subject, emitting in its own colour. Then you use a different excitation wavelength and cube and different fluorophore, for a different bit of your subject. The light source is usually a mercury arc lamp, though LEDs are replacing them because they're made with a narrow colour bandwidth.

Normally you tag a protein or drug or whatever so you can see where it's got to. You can tag cancer cells or TB cells, or things smaller than a wavelength of light. They emit so you know they're there.

Here's a picture c/o Zeiss of a bit of gut, with ten different fluorophores and sets of cubes/filters.

gut.jpg

 

 

Edited By Chris R 1 on 25/01/2019 01:46:02

Edited By Chris R 1 on 25/01/2019 01:49:03

Chris Trice25/01/2019 02:15:06
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1362 forum posts
9 photos
Posted by Emgee on 25/01/2019 00:06:09:
Posted by Chris Trice on 25/01/2019 00:01:36:

Just chucking in the idea of drilling and tapping the end and then screwing in a long high tensile M3 machine screw with the head subsequently cut off.

Chris, You are the 3rd to suggest that or similar so must be a good idea !!

Emgee

Sorry, I skimmed. Reading back I see that. Great minds blah blah blah....

Grindstone Cowboy25/01/2019 02:42:04
124 forum posts
1 photos

How about a bush in that hole to provide a bit of support?

Michael Gilligan25/01/2019 08:52:25
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14011 forum posts
608 photos

Posted by Chris R 1 on 25/01/2019 01:39:15:

This is the bit of microscope, the one existing rod is in place, screwed in a the point arrowed. It IS steel of some sort that it goes into. As you can see the rod goes through a large hole. Quite why they break I don't know.

rod.jpg

It's moving a filter cube in the fluorescence illumination head of a 'scope. [ ... ]

.

That looks unusually poor engineering for Zeiss Nikon Chris ... but I suppose they have 'moved with the times'

I suspect that the reason they fail is that they unscrew slightly, in normal use.

The bending stiffness should be maintained by face-to-face contact; but if the joint slackens the load will be taken by the screw.

Is there room to add a sleeve to the end of your new rod ... to span the joint line question

... it only needs to be a thin tube.

.

MichaelG.

[ tinkerer with microscopes ]

.

Edit: Just noticed the manufacturer's name on the cube !

Edited By Michael Gilligan on 25/01/2019 08:56:03

Edit: for the general interest

https://m.nikoninstruments.com/content/download/16085/353426/file/Fluorescence_Filter_Cubes_2CE-MRJH-3.pdf

Edited By Michael Gilligan on 25/01/2019 09:00:44

Bazyle25/01/2019 09:51:50
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4724 forum posts
186 photos

Another vote for the drill and tapped brass rod with a long grub screw to provide the thread. That way when it is broken you only have to replace the screw in 5 minutes. You could drill and tap the body and put a little line of spare screws in there.

Good idea abouthe sleeve by MG.

Chris R 125/01/2019 10:44:42
29 forum posts
18 photos

Not sure where you mean a sleeve.

There's no space between the surface which has a circular depression in it, and the inside of the end which has the 1.25 sticker on it. Maybe 1mm - enough for a washer is about all. Maybe there was a washer or washer pair once, but there isn't much thread...

On looking closer

rod2.jpg

rod3.jpg

Tell you what, I've had an idea - why don't I drill and tap and cut off an HT screw and.....nerd

By the way if you think that threaded bit looks bent, you're right, it is.

Michael Gilligan25/01/2019 10:52:17
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14011 forum posts
608 photos
Posted by Chris R 1 on 25/01/2019 10:44:42:

Not sure where you mean a sleeve.

[ ... ]

By the way if you think that threaded bit looks bent, you're right, it is.

.

A thin tube fixed onto the actuating rod and a sliding fit on the stub on the cube ... it only needs to bridge the gap.

Your pictures demonstrate my point nicely.

MichaelG.

.

img_2709.jpg

Edited By Michael Gilligan on 25/01/2019 11:08:34

Vic25/01/2019 10:58:50
2255 forum posts
11 photos

As Simon said earlier, a Hex Socket Set Screw would do the job, plenty of suppliers on the auction site but I tend to use Kay’s or sometimes Boltbase.

SillyOldDuffer25/01/2019 11:14:01
4711 forum posts
1010 photos

Looking at the photo, I'd try fitting a brass bush to the hole in the case (ringed in red below). The rod would be a loose sliding fit through the bush. The thread probably breaks because the operator moves the rod sideways whilst turning the knob. Fitting a bush would minimise any sideways forces reaching the screw-end of the rod.

micros.jpg

Best solution is of all to give the microscope to me. I promise to look after it! Don't give it to Michael - I have it on good authority he beats his microscopes to make them work harder and he keeps them in a leaky chicken coop next to a sillage tank full of nuclear waste...

Dave

Michael Gilligan25/01/2019 11:27:08
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14011 forum posts
608 photos
Posted by SillyOldDuffer on 25/01/2019 11:14:01:

The thread probably breaks because the operator moves the rod sideways whilst turning the knob.

.

Nearly right, Dave ...

But the rod works by moving in/out [left/right in the picture] not rotating.

In the jargon: It's a slidey thing, not a twiddley thing. angel

MichaelG.

Edited By Michael Gilligan on 25/01/2019 11:30:06

GordonH25/01/2019 11:36:07
13 forum posts
1 photos
Making a bush for the 6 mm rod would help reduce the bending moment. I wouldn't bother though, I would turn down a larger rod to a sliding fit in the hole then drill and tap the end 3 mm. A 3 mm high tensile grub screw or bolt loctited in would be better than a turned thread.
Gordon
Chris R 125/01/2019 11:51:00
29 forum posts
18 photos

It might break because the operator does it by grope while he peers elsewhere.

Errm, the m3 ole in the cube holder isn't concentric with the ole in the red circle. (The cube holder runs along a dovetail track - which needs some light grease, where can I get something suitable? Not silicone - it wanders everywhere,)

And there isn't a stub on the cube.

 

My wife would love you to pop in and pick up the microscope. I'm told it weighs 105kg. I don't think I'm that strong, but it was a bit of a grunt to get it upstairs (while she wasn't looking).

 

If you're interested in a commercial med application: Probably boring until the result at 1min 40 on.

Auramine-Staining using Primo Star iLED - ZEISS Microscopy

Lots of things fluoresce if you hit them with UV, You don't always need a stain.

This chap uses it, without stains. Look for the pics with the funny colours:

https://photos.app.goo.gl/MV9IynUtBdaKkVj53

 

Edited By Chris R 1 on 25/01/2019 12:04:02

Ken Biddle25/01/2019 11:57:12
10 forum posts
I have repaired a number of these sliders with handles and they usually are plated brass. When t huh e rod is pulled out it is fairly long and is subject to being hit which along with the small thread size tends to break at the prism end. I believe they were designed as a precison instrument sometimes not taking into account the real world.other manufactures have the filter cube wall threaded and the rod will break off leaving the threaded end stuck in the filter usually set with thread locker.
Michael Gilligan25/01/2019 12:03:01
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14011 forum posts
608 photos
Posted by GordonH on 25/01/2019 11:36:07:
Making a bush for the 6 mm rod would help reduce the bending moment. I wouldn't bother though, I would turn down a larger rod to a sliding fit in the hole

.

The clearance hole is in the casting ... How sure are you that it's coaxial with the pushrod ?

MichaelG.

Michael Gilligan25/01/2019 12:06:22
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14011 forum posts
608 photos
Posted by Chris R 1 on 25/01/2019 11:51:00:

And there isn't a stub on the cube.

.

Apologies ... Appearances are deceptive

MichaelG.

GordonH25/01/2019 12:17:24
13 forum posts
1 photos
Quote from Michael Gilligan:- The clearance hole is in the casting ... How sure are you that it's coaxial with the pushrod ?

From the picture and the lack of information to the contrary, I assumed that the desiner had done a competent job and lined them up

Never done a quote before, I hope that my text isn't added to the quoted text Edited to attribute quotation
Gordon

Edited By GordonH on 25/01/2019 12:21:40

Chris R 125/01/2019 12:19:42
29 forum posts
18 photos

Unfortunately there's no space for a flange, inside the casting.

ole.jpg

Edited By Chris R 1 on 25/01/2019 12:21:19

Chris R 125/01/2019 12:21:52
29 forum posts
18 photos

Ole is 8.1mm ish

When the rod is screwed in, hard up to its shoulder, it doesn't run true with its position in the hole, as you slide the cube.

Rod is steel, btw.

Edited By Chris R 1 on 25/01/2019 12:25:38

Chris R 125/01/2019 12:39:09
29 forum posts
18 photos

I see why it looked like there was stub - it was a reflection. Here it is unscrewed a bit.

Trying a bigger pic..scru.jpg

Simon Williams 325/01/2019 14:03:45
412 forum posts
67 photos

As I understand this it's an alignment problem rather than the rod being weak. If so, maybe the solution isn't to make the thread stronger, but to make the rod a bit bendy. I'd try drilling/tapping my favourite grubscrew into the end of a bit of nylon and see if that lasted better.

Rgds to all

Simon

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