What’s this called?

[Gary WoodingParticipant @garywooding25363]

I need to measure the thickness of something that is surrounded by a raised border thicker than the item I want to measure. A calliper like this would do the job, but I don't know what its called and can't find anything like it. Any ideas?

[Gary WoodingParticipant @garywooding25363]

[BizibilderParticipant @bizibilder]

Double ended caliper.  lots on ebay, Amazon, Proops, RDG tools etc

Edited By Bizibilder on 16/02/2023 16:02:12

[Mick B1Participant @mickb1]

Dunno what it's called – maybe double-ended caliper – but why not just make or find a flat piece of known thickness greater than the depth of border that fits inside the border, insert it, measure the total thickness, then subtract the thickness of the insert?

Edited By Mick B1 on 16/02/2023 16:02:04

[Phil StevensonParticipant @philstevenson54758]

https://www.chronos.ltd.uk/product/double-ended-outside-calipers-6/

[egaParticipant @ega]

Woodturners use this sort of thing.

[Gary WoodingParticipant @garywooding25363]

Thank you. I tried X-calliper and cross-calliper. I didn't think of 'double ended'.

Mick: Unfortunately, the item I need to measure is on a curved surface.

[Phil super7Participant @philsuper7]

Try Axminster Tools Under Woodturners Calipers

[Michael GilliganParticipant @michaelgilligan61133]

I need mote Coffee … I’s just taken me five minutes to realise that Gary’s illustration represents the shape of the calliper, and is not a drawing of a Möbius strip

MichaelG.

[Martin King 2Participant @martinking2]

Michael G,

Do i correctly recall a Mobius Bottle?

Also I seem to remember something about a piece of amusing doggerel or poem about it?

Regards, Martin

[Ian PParticipant @ianp]

A friend wanting to measure the thickness of his car fibreglass bodywork made a lash-up double ended caliper with a 80cm throat at one end and a 30mm stroke dial indicator at the other. He made a calibration table to interpret the readings.

Ian P

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin King 2 on 16/02/2023 17:49:38:

Michael G,

Do i correctly recall a Mobius Bottle?

[…]

.

Very nearly

**LINK**

https://en.wikipedia.org/wiki/Klein_bottle

MichaelG.

[Sam StonesParticipant @samstones42903]

Ditto, Michael.

Even now my brain says it's a 3D ribbon loop, that flips between an inside and an outside centre-riveted continuous strap.

Holding the image flat in two pieces of sheet metal fashioned (as Gary intends), into a double ended caliper is a struggle.

Something stronger than coffee at work?

Cheers,

Sam

[HopperParticipant @hopper]

Yes, mobius was the first word that came to my mind when I looked at it.

Such double ended calipers are used by cylinder-head modifiers on car and motorbike engines for measuring how much thickness of metal is left between an enlarged port and thin air or the next port etc when grinding out the ports. So might be available from automotive tool suppliers.

[Gary WoodingParticipant @garywooding25363]

Now I come to look at it, it does look like a Mobius strip. Here's a photo of the 3D equivalent – a Klein bottle.

[Bootlegger BlackyParticipant @bootleggerblacky]

Double glazing measuring tool…

https://www.upvchardwaredirect.com/double-glazing-measuring-tool-glass-gauge-15494-p.asp?gclid=EAIaIQobChMIgqXzzp-c_QIVyMLtCh2fhAATEAQYAiABEgIKnPD_BwE

[egaParticipant @ega]

Eine Kleine Frage:

The liquid in the bottle seems to be above the level of the outlet; is air pressure keeping it in?

[Gary WoodingParticipant @garywooding25363]

You fill it by pumping the liquid through a thin pipe inserted from the bottom and threaded through the 'loop' part. Emptying is the same, but you have to suck instead.

[ChrisLHParticipant @chrislh]

Can't imagine what it might be but is there a practical application of the Klein bottle ?

[egaParticipant @ega]

Posted by Gary Wooding on 17/02/2023 16:52:47:

You fill it by pumping the liquid through a thin pipe inserted from the bottom and threaded through the 'loop' part. Emptying is the same, but you have to suck instead.

Thanks. I think I had forgotten that the essential feature is that there are no conventional openings in the bottle.

[David Davies 8Participant @daviddavies8]

Found this on the 'net.

A mathematician named Klein
Thought the Möbius band was divine.
Said he: "If you glue
The edges of two,
You'll get a weird bottle like mine."

I'll get my coat.

Dave

[V8EngParticipant @v8eng]

Maybe a bit late to the thread but Ceramicists use similar items. Not with same size at both ends.

Link to one of the many suppliers here.

BPS

Edited By V8Eng on 17/02/2023 21:40:45

[Jeff DaymanParticipant @jeffdayman43397]

You will find several choices of the type you sketched Gary if you search Amazon for "Figure 8 Caliper"

[HopperParticipant @hopper]

And if you do a google search for "Digital outside calipers" you will find this interesting mix of new and old tooling. Internal version is also available. Looks very handy for measuring oddly shaped things. And not very expensive at circa 30 Quid.

I have seen the figure 8 type referred to in an American cylinder head porting book as "indicating calipers" but a google search shows nothing under that except normal digital calipers and the above.

Edited By Hopper on 18/02/2023 03:57:45

[DalboyParticipant @dalboy]

THESE are used by woodturners they are not double ended as your picture and yes they are expensive but they do have a metric scale to read off.

I have a set for when I am turning hollow forms

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