Any idea on what this item is?

Any ideas on what this is?

Many thanks

Just looks like an old rotary table to me.

Steve.

Same again ! an interesting rotary table. Noel.

Wierd really how the mind works. I say that because the 1st thing that came to mind when i 1st saw it was a wind up gramaphone. Ok just ignore me.

Steve.

There's no way of holding work to it, and it has a screw and a couple of pins sticking proud of the surface, so you couldn't lay anything on there flat, hopefully someone knows what it is.

Rotary table. Home made with graduations around the edge but I don't think it was used for machining. Light duty worm drive and no hold down slots or holes except for the one long slot and small location dowels. Possibly for mounting a telescope or some other type of instrument ???

Paul

Maybe it was made as a factory fixture to hold a part or a sub-fixture with a part in it for drilling reaming or tapping a series of holes along an arc. Looks like there is an index mark on the left side bearing, so the no of turns could be counted, this would explain my guess about it being for a no. of holes on an arc. The pins and slot on the table might have located the part or fixture, and cutting pressure / operator hand pressure may have been enough to hold things down to the table. As there are no hold down tapped holes or clamping provisions I'd say it was probably not used for any heavy slot milling or radiusing the ends of rods or plates. Just my thoughts on it.

I'd say it is a rotary positioning table but not intended as a manufacturing fixture, more likely a base for a scientific instrument like a theodolite. Could be put to use as a manufacturing fixture though!

Hi Jack, the round table and screw certainly do look more like theodolite parts as you said, or telescope related parts, as Paul said, than factory fixturing components. What made me think 'factory fixture' was that very non-theodolite non telescope-looking heavy T slotted milling style base plate. Could it be the round table and screw started out life as theodolite or telescope parts and were later matched up with the milling base as a re-purposing exercise? Maybe in wartime, to minimize costs / use what was at hand? Very hard to say for sure how it originated, but fun to think about.

Another thought - could it have been used for engraving numbers / lines on an arc shaped path / curved part, maybe a brass protractor type scale? If engraving, the work could be held by hand, and the table might be one off some sort of a Deckel or Rank style pantograph style engraving machine.

Hi, I think it's probably a special rotary table fore marking out or maybe measuring bespoke parts. Interesting to see there are two sets of graduations around the top between that shallow channel and the outer edge and each set is marked 350 through 0 to 110 anti clockwise, or it could have been for a theodolite as said or maybe a laser or prisms or mirrors for measuring other things with lasers, but of course the use could have been for many things.

Regards Nick

Edited By Nicholas Farr on 07/02/2021 08:14:21

I think it's an accessory for an optical table, laboratory equipment or educational. Had similar, but less well made, at school as part of a kit for studying lenses, prisms, interference gratings, polarisation, diffraction and reflection. The kit consisted of a table with a beam light source on which quite complex optical systems could be set up. The rotary table is for accurately measuring how much a prism or lens deflects a beam, or for accurately aiming or collimating it.

Lindsay's example looks old and is well-made from brass on a solid fixture, perhaps for teaching university level optics, or R&D. The modern basic example below is for schools, but precision versions are available too. Don't look up the prices - they're shocking!

When Lindsay's table was new, the laser module pictured above would have been considered proof of Aliens and flying saucers! No idea how lasers work back then, and making one was unimaginably beyond the technology of the day.

Dave

Nick All due respects, but I don't think they would have had lasers when this object was made.

Roy

Hi Roy, didn't know there was a manufacture date on it. I don't think it's appearance has any sway on exactly how old it is either.

Regards Nick.

I agree it was probably part of a Victorian scientific instrument such as a spectrometer. Sad to see it has been canabalised to little avail. The limit of 110 on the graduation might relate to a limit on the maximum difraction angle that will be encountered.

edit. Googling spectrometer shows they are mich lighter build. The heavy handle particularly could put it in the ex-military category in which case repurposing can be applauded.

Edited By Bazyle on 07/02/2021 10:20:24

It has been a long time since I taught physics at this level, but the fly in the jampot would probably have been the screw in the middle and the three studs getting in the way and the lack of any lines, like in Dave's example, to set a prism, lens or whatever so it was rotated and not moved through a circular arc of indeterminate radius

All I could think was: Mukkinese Battle Horn.

John.

My feeling is that the Tee slotted table is a red herring, it looks a bit home made especially the Tee slots which are a bit mis-shapen.

I reckon the brass parts have been robbed of another higher quality possibly optical instrument by a budding model engineer many years ago, and grafted onto the the cast iron base in the hope they will end up with a rotary table.

Phil

Hi Nick Clarke 3, surely sub plates could be made to locate on the studs and have a counterbore for the screw in the middle, whatever needs measuring could then be mounted accurately on the sub plate.

Regards Nick.

I'd 'go with the scientific uses - part of an instrument for regular use or in teaching; but subsequently adopted for some other use; perhaps in a workshop by fitting to a cross-slide. It looks too small and finely made for heavy use but if it was originally intended as a machine-tool accessory, it was in horological or scientific-instrument work

The lack of graduations is only due to the scale, perhaps on a shroud over the worm, having been removed or lost. Note that the worm-shaft still has its minutes scale.

The small pins probably did locate some particular article, as Jeff suggests, but not as original.

I would conclude someone adapted this rotary-table for a very different purpose from original, and I don't think "original" was on even a small jig-borer or engraving machine by any commercial manufacture. I doubt the adapting was by a manufacturing concern either. Unless perhaps under the exigencies of either World War, it would have been more much efficient, reliable and economical to purchase a machine-shop class rotary-table and add the locally-made jigs and fixtures.

Its being mated with a T-slotted slide, suggests to me that Lindsay has acquired the mortal remains of a home-made jig-borer or compound-table for a bench-drill. Or possibly something assembled from bits in a university workshop for use in the Physics Department?