Odd-leg calipers ??

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
But great for marking arcs at a set distance from edges.. The tangents of 2 arcs are a straight line at the set distance.
You can also use them for determining the centre point (intersection of 3 arcs) from 3 edges... of a cylinder, hex, square, etc.
And other uses.
Being taught the purpose of tools makes them more useful, and solves many inaccuracies when precision work is undertaken.
Enjoy learning,
Searching both Blackgates & RDG Tools in the UK for "Odd Leg Calipers" yields Hermahrodite calipers, and Guy Lautard's mentions of Odd Leg Calipers in TMBR show Hermaphrodite as well.

Zoro has these, which should easily be transformed by simply rotating flipping one of the legs:

View attachment 142738
However, at $13.28 I doubt that you'll receive Moore & Wright from Sheffield, particularly since the Country of Origin is listed as "China."

eBay has a NOS listing for 4" M&W calipers for $28+/- (from Canada), and many others (search "firm joint inside calipers")
I call these internal calipers.. for bores.
To mark a line parallel to a straight edge, something like this is so much easier.

The 2p is for scale.
Centre of round bar- use a centre square. Hex or square bar- scribe diagonals corner to corner. To mark out really accurately you need a surface plate/height gauge with scriber.
Hi Dave - I agree. I never use hermaphrodite callipers (never heard of that name before this thread.) for trying to mark a straight line, they were intended (Or so I was taught) for scribing an arc from a side. Always use a scribing block on flat surface, or the engineering equivalent of the carpenter's marking gauge - as you show. The only ways of making a line parallel to an edge (I.E. by transposing from a straight line/surface).
The odd legs that are the original query are new to me, but I can see their use as described in the old book on post#1.
Hi WisJim, I'm just glad if anyone reads the (Tripe?) comments that I write! It's the "old persons' syndrome".... Any conversation is better than talking to the wall... I'm not old but have suffered from it for too long already. (You don't need to reply to that one!).
Did you get a sensible answer that you liked - amidst all the other comments about what odd-legged callipers have been made? I think the sensible option is to strip an internal calliper and re-assemble with one leg reversed was a sensible solution. But I cannot see me doing that as there are other ways of measuring the tool setting (and similar) as described. - I have used a depth gauge/mic/vernier satisfactorily...
And thanks for finding a subject that so many find of interest.
It would appear that "hermaphrodite" calipers are a marking out device, whereas the "oddlegs" are more for measuring/setting dimensions. I would think that both can be replaced by the modern digital caliper ( or even a vernier one). As I previously posted, I have had the ones I have been told are hermaphrodite for over 40 years and never found a use for them.
Hi Dave, Use whatever you are most comfortable with.
Personally, I prefer Verniers to Digital devices, as I find some of my digital things have flat batteries when I need them - or other issues. - Similarly, I prefer slide rules/pencil/paper to calculators and computers because the digital devices can "hide" errors, whereas you must know and understand the calculation to use a slide rule... (I call it fun!).
I was taught the "old-school" methods, because they need you to understand what you are measuring/setting/marking before you start, so a logical approach to the whole process ensures the best accuracy from the tools and measuring devices available. e.g. It is no use measuring to microns if you can't control the settings and machining to that same degree of accuracy. Also. even if you can machine to a high accuracy, if you cannot measure to that same level life can be impossibly confusing/difficult.
Callipers (without accurate scales) are purely comparators, to translate a dimension in a difficult access to one in an accurate measuring device. (e.g. from a bore to an external micrometer). The accuracy of measurement is then one of repeatability of measurement and use of the tools. - This is one aspect of machining I enjoy, as it was a key to stuff I was taught in the 1960s - and later within industry.
Many "hobby" machinists without the training and experience (In my experience) can make very good stuff, but some can't simply because they cannot translate one accurate setting to another.
Hence when people discount "old" tools it is often just because they simply don't appreciate their worth.
Personally, I would need a whole new workshop and tools to make models to the accuracy of the parts in my car.... as most are to 1/10th of the error and variability that I can measure. But the stuff I make works, because it is designed to work at the level of accuracy my tools and expertise can achieve.
Enjoy your hobby!
Hi Andy, Please take me to the office party, I am that kind of bore... but internal callipers are for accurately converting an inside dimensions to an external dimension - not something I would like you to do to me!
Ho Ho HO!
The Moore & Wright Inside Calipers arrived today, and I converted one to Jim's specification:

Inside n Odd-Leg Calipers.jpg

Not quite as easy as I had originally thought: the joint & caliper legs were locked tight and it took a 1/4" drive 13mm socket & wrench on the head of the "screw" to break things loose. Then I had to press the "nut" out of the back leg – the nut had a minimal straight knurl on the end of the OD and the hole in the leg was an interference fit (plus the metal was upset at the hole so I needed to flatten that end ofthe leg). I enlarged the hole slightly so that it was a better but still interference fit, pressed the nut through from the other side and reassembled.

Based on the overall quality, including that of the stamped name & location, indicates that Moore & Wright are letting down the team: while the stamp doesn't say Made in Sheffield England, the M&W branded label on the box does say "Made in The United Kingdom."