[OpenSPIM] OpenSPIM Digest, Vol 42, Issue 5

[David Potter]

Kathleen,

The hole through the stilt is a clearance hole for the M4x0.7 cap screw (or
#8-32 for the Americans) which will mount your 1/2" lens holder to the RC1.
The size standard for cap screws dictates shoulder diameter as 4 mm
maximum. A good quality cap screw is going to have a real world major
diameter measured at the thread of ~ 3.90 to 3.95 mm. The standard diameter
for a close fit clearance hole is 4.2 mm so you would go best with the 4.25
mm diameter. 4.1 mm might work for a short cap screw, long screws can bind
in the hole, but you'll need some "slop" in the fit to allow you room to
move/tweek the 1/2" lens, in its holder, concentric and perpendicular to
the beam axis.

You should note: just screwed together and mounted on the table it is very
unlikely your lens will be on the same axis as all of the parts purchased
and custom manufactured by "you" will have fit tolerances and error
including the concentricity of the Thorlabs doublet lens to the lens holder
it's mounted in. Careful parts and sub-assembly matching will go a long way
in tuning your build.

For what it's worth: contrary to a common held belief, screws don't locate
anything - they simply hold things down. Dowel pins or surfaces locate
items. The part designer here is co-oping the close fit between the cap
screw thread and the stilt hole it passes through in order to use the cap
screw as a poor man's dowel rod. This was very likely done as a cost
consideration as it's an inexpensive solution.

Best of luck with your build.

- David

David Potter
Lattice Light Sheet Microscopy Manager
Monash Micro Imaging - Advanced Optical Microscopy
Monash University Clayton, VIC 3800, Australia



On 20 December 2016 at 05:00, <openspim-request at openspim.org> wrote:

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>    1. Files for parts on OpenSPIM Wiki (Kathleen Chen)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Mon, 19 Dec 2016 11:20:34 -0500
> From: Kathleen Chen <chens18 at rpi.edu>
> To: openspim at openspim.org
> Subject: [OpenSPIM] Files for parts on OpenSPIM Wiki
> Message-ID:
>         <CAGv7iOhrJzyAoVRkdnNdfnCoVo2e-8xoQC89dsFCd-dQLNW_1g at mail.
> gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hello,
>
> My name is Kathleen Chen and I am a graduate student researcher at
> Rensselaer Polytechnic Institute. My lab group is interested in building an
> OpenSPIM according to the specifications provided on the OpenSPIM Wiki.
>
> I have recently been looking at the parts list for the OpenSPIM website, in
> particular the "self-made" parts. I noticed that there are some
> inconsistencies between the PDF version and the STL/STEP files for two
> parts: "RC1 vertical slit stilt" and "RC1 Ø1/2" lens stilt."
>
> Specifically, the measurements in the files are different. For example, the
> inner diameter of the slit stilt is 4.1mm on the PDF drawing, but the
> STEP/STL files show the inner diameter to be 4.25mm. Which measurement is
> the correct one to follow for the manufacturing process?
>
> Thank you,
> Kathleen Chen
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