1/2″ x 40 ME nut

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1/2″ x 40 ME nut

This topic has 33 replies, 17 voices, and was last updated 31 March 2024 at 10:36 by Nealeb.

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28 March 2024 at 19:56 #722736
SillyOldDuffer
Moderator
@sillyoldduffer
Intriguing – it does appear to be a very fine 1/2″ thread, and might indeed be 40tpi. I wonder why though? My guess is it’s to resist vibration when the compass is fitted to a boat. Not good if the only fixing comes undone and the compass falls overboard! I’d Loctite it as well.

Or maybe the manufacturer used a non-standard threads so that spares had to be bought from him.

Dave
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28 March 2024 at 20:37 #722746
Andrew Johnston
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@andrewjohnston13878
On 28 March 2024 at 17:23 matric Said:

I forgot to add: I am in Cambridge (England) so posting shouldn’t be an issue…

Snap! Well nearly, I live in a village five miles west of Cambridge on the A428. I am happy to take a look and make some measurements if required. I also have the wherewithal to make nuts if needed.

Andrew
28 March 2024 at 21:24 #722754
noel shelley
Participant
@noelshelley55608
I’m about 50 miles away, have the materials and could deliver – an excuse for a ride out in the car. Noel.
28 March 2024 at 23:13 #722778
duncan webster 1
Participant
@duncanwebster1
At 1/8 thick, you only get 5 turns of thread even at 40 tpi. I suspect this is why it’s so fine.
30 March 2024 at 14:39 #723123
Nealeb
Participant
@nealeb
This compass was designed for use on a sailing boat, so that as well as the obvious pivot that allows for pitching, what looks like a handle into which the nut holds the compass also has to swivel to allow for the boat to roll – the “handle” is aligned with the fore and aft axis of the boat. A sailing boat does not spend much of its time horizontal! It’s many years now since I sailed on a boat with an identical compass and after that time, I cannot remember quite how the “roll” axis was built. I do remember it as being quite an easy compass to read and steer to.

I hope that this one has a couple of accessories! There should be a cover which fits over the compass with a small window which allows the helmsman to read it and from memory also carried a small light to illuminate the compass card, and with the cover removed, there is a sighting attachment which allows you to take bearings of other objects (fixed or moving) for position-finding and other-boat-avoiding purposes. At least, in pre-GPS, pre-radar, pre-AIS days…

Good to see something like this still in use.
30 March 2024 at 22:09 #723260
Nigel Graham 2
Participant
@nigelgraham2
The 2-axis mounting of a compass – or other instrument or the galley stove – is called a gimbal.

In this case it seems one axis is contained by the semicircular yoke around the compass body, the other axis may be accommodated by the yoke “handle” rotating within the visible, outer part. If so I would expect the outer, tube part to be held in some form of clamp screwed to a suitable point in the boat.

Commonly the gimbal consists of two concentric rings each with a diametrically placed pair of bearings. The inner ring allows the compass bowl to provide swing in one axis, but in turn swings on the outer ring’s bearings on the axis at 90º to the inner pair.

So one axis copes with the boat’s pitch, the other its roll.
30 March 2024 at 22:56 #723277
matric
Participant
@matric
@Nesleb: this is the full story:

Take it or leave it – part II
31 March 2024 at 07:20 #723414
Michael Gilligan
Participant
@michaelgilligan61133
On 30 March 2024 at 22:09 Nigel Graham 2 Said:

[…]
If so I would expect the outer, tube part to be held in some form of clamp screwed to a suitable point in the boat.

[…]

.. as rather nicely conceptualised in the patent that I linked on the previous page.

MichaelG.
31 March 2024 at 10:36 #723445
Nealeb
Participant
@nealeb
The Sestrel Moore compass I remember using was around 45 years ago, on a 40′ gaff ketch. Lovely boat. She was wheel-steered from a fixed position behind the deck saloon so this style of compass worked fine, and there was plenty of space under the boom. My own boat was a 28′ gaff cutter, and despite the traditional styling I fitted a couple of modern bulkhead compasses to read from either side of the cockpit. More practical if less “atmospheric”! The fact that there was a slight bend in the bulkhead so that there was a 2deg difference between the two compasses was never mentioned!

Nice to see that these compasses are still around – brings back some good memories.
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