Leitz Laborlux focus block question

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Pitufo
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Joined: Sun Jun 21, 2015 4:32 am
Location: United Kingdom

Leitz Laborlux focus block question

Post by Pitufo »

I am currently stripping the above mentioned block, this particular one is a Laborlux S but it looks very similar to the Laborlux 11 and 12 shown here.

PDF brochure here http://earth2geologists.net/Microscopes ... ochure.pdf

EDIT: Instruction Manual for Laborlux S here http://earth2geologists.net/Microscopes ... ctions.pdf

These models have a common problem - the focus seizes but both of the black plastic fine focus controls (and one of the coarse focus controls) can be moved freely. One coarse focus is seized solid. I have come across the same fault several times.

I am having difficulty removing the black plastic focus controls from the sides. Does anyone know how to do this? If so, I would be very grateful for any suggestions.

There is a small black hole in the side of the fine focus control where you would expect a hex key might fit but it just appears to be a hole.

A service manual would be very helpful but I haven't managed to locate one.

I will post some photos but having difficulty uploading at the moment.

Kind regards,

John
Last edited by Pitufo on Sun Aug 05, 2018 12:51 pm, edited 4 times in total.

Pitufo
Posts: 260
Joined: Sun Jun 21, 2015 4:32 am
Location: United Kingdom

Post by Pitufo »

Photos now loading - see below.

A small hole (2mm diameter) is visible in the fine focus control. I have managed to peer inside the hole with a stereo microscope but I can't see a hex nut or cross-head screw.
Last edited by Pitufo on Sun Aug 05, 2018 1:08 am, edited 4 times in total.

Pitufo
Posts: 260
Joined: Sun Jun 21, 2015 4:32 am
Location: United Kingdom

Post by Pitufo »

Image

Image

enricosavazzi
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Post by enricosavazzi »

I don't have direct experience with this particular rack, but I cannot think of any other purpose for the hole in the side of the fine focus knob, other than passage for a hex key or screwdriver. The screw itself can be some distance inside the hole (some 10 mm is typical) and the screwdriver can wiggle sideways in the hole quite a bit, which means it takes some probing with a hex key or screwdriver at different orientations before you will find your target. Also, not knowing the size or type of the screw means you may have to try a few ones before you get the right tool in the right place.

If against all odds there is no screw behind the hole, sometimes the fine focus knob is held to the axle by a nut or screw hidden behind a metal or plastic disk on the top of the fine focus knob (which I cannot see in the pictures).
--ES

Pitufo
Posts: 260
Joined: Sun Jun 21, 2015 4:32 am
Location: United Kingdom

Post by Pitufo »

Thanks Enrico. I'm sure you are right.

I will continue to rummage around. I managed to see down the hole a little with a stereo but the no luck yet.

There is no cap on the end of the fine focus as is often found (it is a single moulded plastic piece).

Pitufo
Posts: 260
Joined: Sun Jun 21, 2015 4:32 am
Location: United Kingdom

Post by Pitufo »

Success. A 1.5mm hex key is required. It was quite hard to find the hex nut as the fine focus control had rotated out of position, so I had to turn slowly while looking down the hole with a stereo.

I will post some photos later. Whether I can get the thing to work (and then back together again) is another question...

Pitufo
Posts: 260
Joined: Sun Jun 21, 2015 4:32 am
Location: United Kingdom

Post by Pitufo »

A few photos showing the disassembly steps, in case it is of use to someone in future.

Only the right side fine focus needs to be loosened. The left side fine focus can be left on the axle.

Image
Image
Image

The coarse focus controls are quite tricky to remove. There are two cross-head screws located on the underside - a cross-head screwdriver needs to be angled in from the stand side.

Image

The fine focus mechanism seems to work fine and the visible central gears can be rotated easily. However the brass barrels on each side will not turn relative to the central steel section. I think this is where the problem lies.

Some crusty green gunk was visible at the meeting point of the steel centre and right hand brass section. This green crust is often found on seized joints in my experience (Does anyone know what it might be? Copper carbonate possibly? If so, I wonder whether vinegar might help).

So far it has resisted my advances, including drops of IPA and light viscosity oil which I have found sometimes does the trick. Also gentle heating of the brass has not helped so far.

Any suggestions welcome.

The right hand side brass section has two screws on it which I would like to remove but they are very tight and I don't want to destroy them, so I think I will wait for another tool (T-handle Rapidadaptor) which I think might be more use than the screwdrivers I am currently using.

Image

ChrisR
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Post by ChrisR »

That looks fairly frightening. ANother pair of hands for those screws would probably help.
If the assembly is parallel-sided, you may be able to put a screwdriver bit in a pillar drill (turned off) to hold its angle straight.
If the max force you feel like applying doesn't move things, try:
(in principle)
maintain that force, and put a rigid metal spanner(wrench/bar) on the chuck/screwdriver bit, and tap it with a light hammer in the undoing direction. The shock on top of the static force may well work.
I have a manual "instrument" impact-driver which is very light, designed for very small things, and a normal one is also OK if you have spare hands and a careful touch.
An obvious type to try is what you get in a cordless drill/screwdriver, good ones adjust to a very low level.
Chris R

Pitufo
Posts: 260
Joined: Sun Jun 21, 2015 4:32 am
Location: United Kingdom

Post by Pitufo »

Thank you very much for your helpful suggestions Chris.

I actually managed to free the brass section (without further disassembly) by screwing the steel axle back into position and then gentle applying pressure to the brass end using a cheap plastic pipe wrench (these also work well on stuck objectives - but can remove lettering so use with care). Very little force was required. See photo.

This was after several rounds of very small amounts of IPA then light viscosity oil applied at a few points around the brass/steel interface.Image

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