MicrobeHunter.com Microscopy Forum

This RMS-threaded object recently came to me. It has a sort of blunted hypodermic needle that communicates to a very small cavity at the back. It is open and would leak, but is threaded so there might be a plug. With a plug installed there would be only a few cubic mm of volume left. By means of the small knurled area it can move down about 6mm and back.

The needle doesn't look suitable as either an ink marker or an engraving tip. It appears to be made of an ever-so-slightly magnetic stainless steel. There's no sign of the threaded cavity it communicates to ever containing ink (or anything else). The slip fit between the brass outer body and the aluminum inner "piston" (knurled at the end) doesn't appear to be leak-proof.

Were it to dispense immersion oil, seems it would leak fore and aft.

The movement of the tip itself is not spring loaded. It will drop by gravity. So it's not something one would want to mount on a turret and swing into play if the tip were actually meant to contact a cover slip.

The tip doesn't seem hard enough or of a geometry to work as an indentor or a scribe.

Anyone know what it is?

Pretty heavy knurling, more reminiscent of hose fittings than microscope parts.

Were it now for the trouble someone took to send this out for chrome plating after machining and knurling the brass body, it might be a shop-made one of a kind.

I've never seen an RMS thread on a hose fitting. So, still a mystery . . .?

Hi Pete,
this looks very much like a pen used to draw technical drawings that were to be reproduced by a classic optical method. This drawing ink was applied by a pen consisting of vertical tube, a wire with a weight to allow to free the nozzle by shaking, and in the back a labyrith seal that allowed for limited air access. You might google for Rotring Isograf and Rapidograf. I learned technical drawing in my studies and the final step was always to draw all lines and text with technical ink. This is not ink like in a fountain pen but more fine black flakes in a fluid, forming a very light proof layer.

I know that this has been used in microscopy to mark objects with some kind of permantent paint. For a single circle not much paint is needed so this item is perhaps as complete as it ever was. You could dip it in a bit of slow drying paint and then paint your ring. Ah: Object markers have a pen tip that is excentrically mounted, to allow the painting of a ring - is this the case here?

Bob

I've never seen an RMS thread on a hose fitting. So, still a mystery . . .?

Looked up pipe fittings. Apparently there are two standards, British and American.

Here is an article on the RMS thread: https://www.sizes.com/library/technology/RMS_thread.htm

and one on the British Pipe Standard: BSPP: https://amesweb.info/Screws/bspp-thread ... lator.aspx

The basis of both seems to be Whitworth

Looks to me like it might be a sampler, swung round on the turret when a sample is needed from a specific area of an uncovered culture dish. Turning the knurled section would dip the hollow tip into and out of the sample medium, later retrieving the contents for further analysis.

The pen and sampler ideas both seem possibilities, thanks.

As a Rapidograph-like pen, it's missing the needle and weight. Still could be. Having entered my seventh decade, Bob, I still have Rapidograph pens, Kodak Carousel projectors, and the like still around. Just got rid of the Teac reel to reel tape deck - according to one article they are now back in fashion as the "new vinyl."

As a sampler, maybe.

The design flaw for either is that it isn't spring loaded; and so wouldn't stay up when the turret was moved. Instead, it would drag across the cover slip, slide, dish, etc.

Maybe this was meant to be plumbed somehow at the nosepiece to dispense a reagant or ???

Perhaps it serves the same function as this:

https://flmicroscopes.com/collections/n ... ect-marker

JGardner wrote: ↑

Sat May 02, 2020 8:29 pm

Perhaps it serves the same function as this:

https://flmicroscopes.com/collections/n ... ect-marker

I have one of the Nikon object markers. This one is quite different, still somewhat a mystery to me.