Unidentified Rule

This topic has 16 replies, 10 voices, and was last updated 26 February 2018 at 20:22 by James A.

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25 February 2018 at 11:10 #343141
James A
Participant
@jamesalford67616
Good morning.

This rule, which appears to be made of either bone or ivory, was amongst my gandfather's tools who was an engineer, designing tools. I have absolutely no idea what it is for or whether it is even a measuring rule at all.

I should welcome any information on it.

James.

Edited By James Alford on 25/02/2018 11:10:48
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25 February 2018 at 11:10 #33160
James A
Participant
@jamesalford67616
25 February 2018 at 19:30 #343192
Neil Wyatt
Moderator
@neilwyatt
I'll dive an and say … I haven't gota clue.

One interesting thing is that the angle scales measure out from the centre.

The straight scale appears to be ordinary inches from the end.
25 February 2018 at 19:59 #343201
Brian H
Participant
@brianh50089
Could it be a scale rule?

Brian
25 February 2018 at 20:01 #343203
Martin King 2
Participant
@martinking2
Hi, it is an Ivory sector rule, very nice item, is there a makers name?

Martin
25 February 2018 at 20:04 #343205
James A
Participant
@jamesalford67616
What puzzles me further are the letters at the end of the rule. On one side, it has S, T and T. The has L, S and C. A third set of lines has T*, S* and N*.

I have just noticed that even the thin edge has numbers and a scale.

I cannot find a maker’s name, but there are the initials FOL.

Ummm. What is a sector rule?

James.

Edited By James Alford on 25/02/2018 20:09:21
25 February 2018 at 21:06 #343223
not done it yet
Participant
@notdoneityet
“What is a sector rule”

There is a fairly comprehensive explanation on Wiki
25 February 2018 at 21:06 #343224
michael potts
Participant
@michaelpotts88182
Hello James.

There are currently seven sector rules on ebay at a variety of prices, all fairly high, all similar to yours.

Wikipedia has a long explanation detailing the various scales on the rule. Further editing seems to be needed on most of the scales. The origin of the rule appears to have been Italy in the early seventeenth century. It allowed the user to perform a number of calculations, some stated, and others described as 'complex'.

Put 'sector scale' into google or whatever, and be prepared spend some time looking at the various items that come up, because it does not take long to become complicated and complex.

Regards. Mike.
25 February 2018 at 22:07 #343228
James A
Participant
@jamesalford67616
Thank you for all of the replies. I have had a look at Wikipedia which I shall need to read more carefully later. I had wondered whether it were some sort of technical drawing aid, but I was obviously wrong.

Thank you.

James.
25 February 2018 at 22:21 #343233
Martin King 2
Participant
@martinking2
Good English makers increase the value of these and they can be highly collectable. Does it have tiny brass 'buttons' with a dimple in the middle for divider points to avoid wear?

Martin
25 February 2018 at 22:55 #343238
James A
Participant
@jamesalford67616
Martin.

I have just looked at the tiny brass buttons at the ends of the rule, using a magnifying glass and testing with a divider point, it does have the dimples in the brass inserts.

James.
26 February 2018 at 07:02 #343249
Speedy Builder5
Participant
@speedybuilder5
James – Sine, Co-sine and Tangent ,Log ,T* – Tanh, S* – Sinh, C* – Cosh. I don't remember how they worked, but seem to remember something at college 50 odd years ago when we made our own on white card strips.

Ah – the web to the rescue

BobH >**LINK**
26 February 2018 at 07:49 #343251
Martin King 2
Participant
@martinking2
Hi James, Looking at the middle 2 pics it appears to me that possibly it is bone not ivory, particularly as there is no makers name. Does close inspection show microscopic porosity in the stained brown areas near the hinge joint?

Also the slight warping in the middle is more common to bone.

There are varying quality types of these, some also made in boxwood.

Cheers, Martin
26 February 2018 at 08:29 #343253
pierre ehly 2
Participant
@pierreehly2
hi,

French & English sector (the ancestor of computer)

pm
26 February 2018 at 11:17 #343272
KWIL
Participant
@kwil
Fascinating, I want one.
26 February 2018 at 14:52 #343283
Brian Sweeting 2
Participant
@briansweeting2
Slide rule forerunner perhaps?

Damn clever our forebears weren't they?
26 February 2018 at 20:22 #343345
James A
Participant
@jamesalford67616
Martin:

I have had a look at the material with a magnifying glass. Rather than porosity, the structure seems to be more like very fine lines, like the grain in some cuts of beech wood.

BobH: thank you for the information about sines et all and the link to the web page. I have had a look at it and it has shed a lot of light on the tool. All I can say is thank goodness for modern calculators.

Regards,

James.
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