Re: Servicing a Swift FM-31

On Dec 25 2008, 1:05 am, UKoncology <UKOncol...@xxxxxxx> wrote:
On 13 Dec, 15:42, UKoncology <UKOncol...@xxxxxxx> wrote:





On 13 Dec, 11:32, shiraz14 <shira...@xxxxxxxxxxxxxx> wrote:

On Dec 12, 6:01 pm, UKoncology <UKOncol...@xxxxxxx> wrote:

On 11 Dec, 20:21, Kevin Cunningham <sms...@xxxxxxxxxxxxxx> wrote:

On Dec 11, 7:52 am, UKoncology <UKOncol...@xxxxxxx> wrote:

Has anyone any advice on adjusting the stage travel on this scope,
please?
It works just fine, and is surprisingly good for an ultra-portable,
but currently brings to focus at the extreme of focus adjustment. I'd
like to adjust the rack and pinion so that focus is achieved nearer
the middle of the adjustment range. Thought I'd ask first, in case
removal of the cover of the r&p is likely to provoke a flying spring
problem. If anyone has stripped doen one of these, I'd appreciate any
tips.
Thnx, HJ

I'm not sure I've done a 31 but Swift is One Of Those Companies.  I
did a bunch some years back, all the same, but they were built by
different companies and didn't even use the same light bulbs.  Same
model number though.  Swift has never actually built a microscope,
they just ask for bids, low bid wins.

Are you really sure you want to make these changes?  Most microscopes
are designed so that focus will occur in the last 5% of vertical
travel.  That's so it's harder to damage the high NA objectives by
colliding with the stage.  Usually if you have to make that drastic a
change you will have to re-machine the back focus area, that's not
that easy to do, you need a good machine shop and it helps to have a
couple of microscopes so if you screw up the first one, a 50-50
chance, you go on to the next one.

Are you sure you want to do this?

Kevin Cunningham
SMS

On reflection, Kevin's last question is indeed very sound advice! The
answer is - only if it is straightforward. And they are quite
expensive! (though mine wasn't)
The FM-31 is a strange beast - an inverted portable about 7" long x2
x5. The overall design resembles a Macarthur but is quite different,
and there are no related designs that I have seen. The slide is viewed
inverted - cover slip down - and focus achieved by raising and
lowering the stage.  The total extent of travel is only a couple of
mm, and this is clearly intended, as there are a couple of black lines
on the moving sections indicating the limits.
BTW - these are quite serious instruments - well worth picking one up
if the opportunity arises. Optically, they are rather good, and better
than any of the traditional Swifts that I have tried, so the notion
that they are manufactured by someone else is interesting. They are
pleasingly solid, and very well engineered, but not in the same
league, of course, as a Nikon model H, though much more affordable.
Thanks for reminding me of my limitations, Kevin - I shall take your
wise advice and leave it alone!
best wishes, HJ- Hide quoted text -

- Show quoted text -

Hi,

Yes, you should take Kevin's advice (not only because the range of
travel is limited to the last 5% to protect against collision with
the
high NA objectives as Kevin has mentioned, although the FM-31 employs
long WD objectives, but also due to the fact that this actually
allows
you to view specimens which may be relatively high (e.g. a barnacle
cemented on a relatively small but high rock sample/pebble) through
inverse mounting on a slide and
raising the stage.

All the best for your field studies ...

Best Wishes,
Shiraz

Thanks Shiraz, my problem is that my x40 objective is not a LWD
objective (if anybody has one for sale, I'd be glad to hear from
them). However, I have found a low-tech solution by adding a thin
brass *** shim under the stage. this has the effect of raising it by
1mm, sufficient for my purposes. Dead easy to do, as well.
Thanks everybody, HJ

Just for the record, I've solved my own problem without the shim.
The answer is, in fact, trivial!
Under the square plate on top of the scope is a spring. Remove the
spring and lift out the stage casting through which is a 1cm x 3mm
grub screw. There is a tiny lockscrew holding the latter. The
grubscrew bears on a the side of a cone on the focussing spindle,
which moves laterally, and moves the grubscrew and stage vertically as
it does so. Altering the length of the grubscrew adjusts the travel.
Half a turn, tighten up the lockscrew, and you're done. Don't lose the
spring or the tiny lockscrew which should be loosened but not removed
unless you have very good eyesight.
Posting this just in case it helps any other FM-31 owners.
Thanks to all for advice. HJ
Fin!- Hide quoted text -

- Show quoted text -

Hi HJ,

Congratulations!

I don't own the FM-31 though, only noticing some pictures of it off
the Web, however from your description of the grubscrew as being the
main determinant for stage travel, yes, this is often the case for a
typical r&p system - what however is the main concern for worry in
this case, is that in future, you might potentially face backlash and
drift dilemmas occuring in the stage Z-travel of your FM-31 (as you've
tampered with the key regulator of the r&p mechanism).

Nevertheless, it is also probable that by that time, you might most
probably be considering the purchase of a new scope, so all the best!

Regards,
Shiraz
.

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