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Member postings for Dave Martin

Here is a list of all the postings Dave Martin has made in our forums. Click on a thread name to jump to the thread.

Thread: Gosh trying to line a Loco is so hard any tips
20/10/2016 08:46:02
Posted by Neil Wyatt on 19/10/2016 21:44:51:......

Is it a good idea to have someone sat in the tender when its balanced on the stand?


Spot the shadows?

Thread: Tide recorder ?
07/10/2016 21:28:46
Posted by Andy Freeman 1 on 07/10/2016 19:48:24:

Today I went on a tour of RRS Discovery, a National Environmental Research Council ship that was visiting Liverpool. Some fascinating underwater probes, submarines, autonomous torpedos.

One thing that interested me was what I think is some kind of tidal chart recorder. Has anyone seen one of these. The instrument is powered by a small motor.

If all the cams are fixed, surely it would always repeat the same trace on the paper?

More photos in my album

Tide recorder

Edited By Andy Freeman 1 on 07/10/2016 19:49:15

Andy - as other have said, I think its a simple tidal predictor. If you're in the Liverpool area, you may have heard of the Proudman Oceanographic Laboratory at Bidston, that housed the Doodson tidal predictor.

Dave M.

Thread: Holding short lengths
06/10/2016 14:14:08
Posted by Raymond Anderson on 05/10/2016 14:28:38:

For ***** sake JS give it a rest , you're beginning to sound like a "parrot ". now please take note, I like soft jaws, no, I LOVE soft jaws, but It's going to be collets for the DSG. [ as well as the soft jaws ] Maybe I should put an advert in the Guardian in ten inch deep banner headlines "Raymond really does like soft jaws " but he's going for collets.smiley.

Raymond - I would suggest you think about taking your own advice. After your thread on ER collet issues, JS started this separate thread to discuss methods of holding short length workpieces. This thread is not about what you have decided to do....

Dave Martin

Thread: Alternative to PC based Cnc controllers
03/10/2016 02:11:48
Posted by Bazyle on 02/10/2016 22:12:59:

Yes it was the manufacturers I meant were missing out. I thought the inbuilt display a bonus for the applications I was thinking of, like small industrial oven process control (not everything is CNC) greenhouse control, central heating control, alarm system, that sort of thing.

Older PC beside me loading Linux over windows NT. Fingers crossed the 10G drive and 250meg memory is enough. It didn't self select to install the desktop so knows it's tight.

Bazyle - for non-CNC control applications, there are already small PLC controllers with integrated displays, such as the £270 Cubloc CT1820 with graphics, touch screen display, programmable with scripts or ladder logic; other smaller ones available which could be used to control an ATC etc.

Dave (no connection with CuBloc other than as a user)

Thread: extra-fine knurling
30/09/2016 09:15:01
Posted by duncan webster on 30/09/2016 00:47:28:

All this got me thinking. as the purpose of knurling is to increase the friction when turning whatever has been knurled, surely a straight knurl is what you want? Normal to the circumferential force. Why do we use diamond? Is it easier to create?

Two reasons I can think of - firstly, as Duncan suggests, it may be for production reasons / more forgiving of slight misalignment. The second is that if it is the head of something that needs to be pulled, diamond gives grip when applying axial force.

Thread: Sweating Plastic
11/09/2016 13:31:45

If it was just on the outside I would have suggested it could have come into contact with some form of spray (polish / air freshener / insect killer ...) which had reacted with the plastic.

The likes of padded car dashboards and flexible cable can exude plasticiser, but I've never seen it on a TV case and would wonder why they would be needed on something that should be rigid? Plasticisers work by preventing full bonding between molecules of the base plastic, and the un-anchored plasticiser molecules can migrate to the surface, especially under heat. Plasticisers contributed to the 'new car' smell in the 70s/80s; and can also the reason that flexible cables left undisturbed for years have a coating of grime - nothing to do with static but that the dust sticks to the film of exuded plasticiser.

If it was exuding like plasticiser, I think it would just be a surface film rather than the blisters you describe - that sounds more like a manufacturing defect - maybe the back was laid up from an impregnated mat but the materials weren't properly prepared or processed.

I would suggest it would still be worth contacting the vendors as there might be a latent defect which is emerging which they might already know about and/or might wish to investigate.

Regarding 'could it be dangerous or toxic' I would suggest treat it discretion until you know otherwise.

Thread: Is CNC cheating
04/09/2016 10:10:09
Posted by John Stevenson on 04/09/2016 09:08:00:
Anybody else thinks we have missed the point and are now onto armchair semantics ?

Don't open any more cans of worms! - next thing we'll have is angst about whether you should have declared if it was an Ikea armchair or a hand-bodged chair made from greenwood on a manual pole-lathe! wink

Dave (IOM) - one of the 'silent majority' who hasn't voted, who has never built a model but uses the most appropriate manual or CNC machine when needed.

Edited By Dave Martin on 04/09/2016 10:15:12

Thread: Sequence of huge explosions
04/09/2016 09:54:16

Could they have been supersonic bangs?

Thread: Churchkhela
23/07/2016 09:28:37

Thanks Neil - that brings back memories - I've enjoyed both Churchkhela and Khachapuri!

A ship management company I used to work for had a Georgian fleet under management, and I used to sail with then from time to time - marvellous people, and I had a Georgian ex-Radio Officer Evgeniy (pronounced zhennnya) on my team for some years.

Have been given (and enjoyed) Churchkhela onboard but possibly best export from Georgia is their champagne. Cooks onboard would prepare Khachapuri but would bemoan that they couldn't get the right sort of melting cheese to fill the bread boat.

Some ingredients were the same but just different dining habits.... One of the first trips with this fleet, a Fleet Manager and myself had just joined and sat down to lunch. Fred, a typical Scots Chief Engineer and very dear late friend, was renowned for taking a few teaspoons of water in his coffee (I think the recipe was 3 spoons coffee and 4 spoons sugar) but on this occasion there was a pot of tea on the table so Fred poured himself a cup - and relished it. In his Maybole accent he said:
  Fred: "That's grand tea - is it a special Georgian one?"
  Cook: "No, just ordinary tea"
  Fred: "Really - what sort of tea is it?"
  Cook: "ordinary Lipton Yellow" (which they called most loose black tea)
  Fred: "Well how does it taste so good - how do you make it?"
  Cook: "Put half packet tea in pot and add water!"
There was a jug of boiling water on the table as well - and in fact what the officers were doing was pouring maybe 1/8" of this tea from the pot (with the colour and consistency of Camp coffee essence) and then filling the cup with boiling water - whereas Fred had filled his cup with the concentrated tea - maybe having the equivalent of an ounce of tea!

Interesting ships as well - there was a remarkably capacious second radio room at the back of the accommodation, which by then only held the weather fax receiver - an excellent Russian set with what appeared to be better sensitivity than a Muirhead or JRC set, but the same ozone! That compartment, when the Georgian merchant vessels were trading under of the supervision of the Black Sea Fleet, had housed various radio monitoring equipment.


Edited By Dave Martin on 23/07/2016 09:29:18

Thread: What Did You Do Today (2016)
21/07/2016 09:02:55
Posted by Michael Gilligan on 19/07/2016 13:39:49:
Posted by Andrew Johnston on 19/07/2016 13:34:21:

That's because it's nowt to do with product safety..................



Sorry, Andrew ... I don't understand

Safety recall on 190,000 power supplies

... Presumably you know something about this that I don't.


Michael - I think Andrew was referring to the way that some suppliers are pushing to install smart meters on the grounds of safety.


Thread: Mystery Tool?
07/06/2016 11:13:25

Thanks Peak - as I suggested I thought they were ear-marking pliers and from the chart it's a combination of AZ and a CW variation. It could of course be used for marking hides etc. but I'm pretty sure its for cattle earmarking.

04/06/2016 22:05:37

Martin - just possibly its for putting identification notches into livestock ears? - on our farm we had various single-notch pliers but never saw a multiple set though.


Thread: Form Tool or other way?
21/05/2016 10:44:34

James - can't offer any more advice on the pulley but super-impressed with your machinery restorations.


Thread: BH600G Fine Feed Help
12/02/2016 09:04:54


If you haven't already seen it, have a look at this thread on a belt conversion - lots of useful real-world info from "Earl John".


Thread: Merry Christmas to one and all!
25/12/2015 15:28:03

Nollick Ghennal as Blein Vie Noa (Happy Christmas and a Good New Year) from the Isle of Man.


Thread: Three cornered Philips type screwdriver
21/12/2015 11:36:18

Brian - try searching for "tri-lobe" or "tri-wing". Cheapest may be a bit set such as this one.


Thread: Harrison lathe oils
21/12/2015 11:12:01


if the '68' is for the ways, if you can't find a Shell Tellus you should be able to find Mobil Vactra 68 which is what I use on my machines.


Thread: 3 jaw chuck D1-3 pins loose as a goose
21/12/2015 08:44:58
Posted by John Rudd on 21/12/2015 08:17:15:


Toward the end of the video, you mentioned the position of the locks being between the v symbols and adjusting the height of the pins on the back of the chuck.....does this mean that it is possible to have the pins set at differing heights?

Great explanation btw...yes

John, yes, the idea is that if the indicator mark on the cam lies between the two V-marks, that effectively equates to the tolerance for one thread's pitch on the backplate. This way (as I understand it) the backplates, and indeed the pins, can be 'free tapped/threaded'. The cam will always be clear of the pin bore when the mark on the cam is aligned with the mark on the nose at 12 o'clock above each pin; if the cam locks-up when its index falls between the V marks then its safely locked. On my Chester "Cub" lathe's D1-5 nose, it doesn't have the pair of Vs as Nick showed, it just has one mark at 12 o'clock and another at about 4 o'clock and at first I did needlessly worry that not every pin on every chuck locked at exactly the same position.

Dave (not Nick!)

Edited By Dave Martin on 21/12/2015 09:14:05

21/12/2015 08:26:24

Thanks Nick, a great explanation. A couple of things (as a D1-5 user) I'd add are:

1/ Reference the original question, the cam pins are a 'loose' fit for a reason. If the pin was fitted rigidly to the chuck, the axis of the cut-out in the pin would need to be on exactly the same radial axis as the cam in lathe nose - if it was out by even a degree or two all the cam effort would be on one edge of the cutout with potential damage to the cam and galling to the pin. Having a degree or two of float in the pin allows the pin to self-orient itself to the cam when the first pressure is applied; also the threads are often tapped a little 'loose' to ensure the pins can move sideways a tiny bit to avoid fighting with the tapered-register alignment between the backplate and nose (in some ways analogous to a floating reamer holder).

2/ If anyone ever need to replace camlock pins, just be aware that whilst the visible part of the pin is standard, the threaded portion that mates with the backplate can have different threads (I once bought a pin-less chuck and found none of my existing pins would fit - metric vs. imperial)

3/ If changing pins, there's often a groove scribed around the pin, screw it in until that is level with the register face of the chuck, then pop the locking screw in - then, as Nick said, don't be surprised if you need to go in or out a turn.

4/ If, rather than a 3-cam, its a 6-cam chuck/nose, then recommended sequence for nipping/tightening is 1,3,5,2,4,6 to avoid risk of pulling chuck off-centre

5/ Especially if its a really heavy chuck, always try & bring each cam to the top before tightening to counteract gravity

6/ I'd always use a board between the chuck & bed just in case!


Edited By Dave Martin on 21/12/2015 08:56:48

Thread: What did you do today (2015)
23/08/2015 23:23:19
Posted by Bob Brown 1 on 23/08/2015 23:00:35:


"There have been collisions between gliders and light aircraft in open airspace (Class G) in the UK. Although gliders are classified as aeroplanes, powered aircraft are supposed to give way to gliders in open airspace."


Bit like steam gives way to sail see **LINK** that doesn't work either



"Steam gives way to sail" is broadly the rule in the open sea, but according to the International Regulations for the Prevention of Collisions at Sea (the "ColRegs" ) vessels which are constrained by their draught have pretty much right of way when in a channel - there's lots of water for light draught yachts, not for large merchant vessels. During congested periods such as Cowes week, Southampton harbour master sometimes deploys their own boats to try to keep the channel clear (especially around the Bramble Bank turn) but the swarms of racing & spectating yachts can be even too much for the harbour master / QHM to control.

In this case, the skipper of the yacht was found guilty of a number of offences & heavily fined.

Edited By Dave Martin on 23/08/2015 23:26:34

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