Member postings for martyn nutland

Hello All

Thought you might like to see a few photos and it in place on the pivot plate and, this, hopefully, is how it's supposed to work. With renewed thanks to everyone who commented and advised, without whom I'd have probably have made a banjax.

Best Martyn

What it was Duncan, was that until you highlighted the fact that the main axis (segment) and that of the stud/lug were not that far apart, I was not clear as to how much off-set I might need and I was worried the jaws on the chuck I was using (150mm diameter I think) might not be able to accommodate it. That was silly. And as it happens, it didn't arise.

Thanks again (and everybody) for the most helpful guidance. Martyn

Thank you, Stuart. This was my original thought - more or less. I now have two options. Making it in two parts is definitely simpler, but is not as it was done originally. But then, that doesn't really matter because it was probably a stamping job and certainly not machined. My nervousness about trying to make it as one piece centres on off-setting when there's such a disparity between the diameter of what will be the segment (41.5mm) and the button (about 13mm). As I said to Duncan, I've probably made an initial mistake in not using my larger four jaw that would have given me more latitude (sic). I'll let folks know how I get on.

Meantime, many thanks all. Martyn

Got it, Howard. Thanks. The consensus seems to be, then, make it in two parts and forget machining as one piece. Fair enough.

Martyn

Hello Fellow Hobbyists

I am wondering whether anyone would be interested in preserving a very early Drummond lathe. My information is that it is No 7. I assume that that is its serial number, although not being familiar with Drummonds I may be wrong - it might be the model.

It belonged to my late uncle and is now owned by his son. It would certainly make an attractive addition to a collection of historic machine tools but is a viable proposition as a hobbyist's lathe. It currently 'lives' on the Isle of Wight.

If you are interested and want more information please contact Paul Leinthall-Cowman on [email protected] 01905 356482

Best Regards, as always, Martyn

Thanks for the extra comments.

I think the consensus on the simplest way to do this is to make ascending 'steps' (i.e. effectively tapers in both directions but in steps) using a narrow grooving tool, then blend them together with a flat file. That's what I'll do.

Martyn

John

Suspected it was like that; but most graphically expressed. Almost poetry. Thank you.

Thanks too Hopper for the toe tip. Not only bolted to the bench but bench bolted to wall eh.

Best from Martyn in sunny France.

Addendum!

As regards the thread - I've seen the major diameter expressed as 1.475 inches, which is about 37.4mm isn't it?

Martyn

Hello Everyone

I wonder if I might pose a couple of questions and try out an idea on the experts?

I want to make a bronze vintage radiator cap (I do know I could buy one but they seem disproportionately expensive and I like to make things!)

I thought... if I bought a nut of the same thread as that on the neck of the header tank, I could turn off the hex on the lathe, mill a bronze replica of the original cap and solder or braze it to the nut. Simples! Job done.

However, I can't for the life of me, and after consulting every table I can find, determine what the male thread is. The major diameter is 37mm 16 TPI. Any ideas?

Now I acknowledge the proper way to do this job is start with raw bronze and cut the female thread on the lathe, but I don't feel I have the competence or confidence to do this, not least because there are a few fundamentals I'm unsure of.

I use a Chester Super B lathe configured for metric. Assuming I know the lead screw pitch, can I gear a metric lathe to cut imperial threads, as would be required (I guess) for the radiator cap. And if I can, and someone knows the thread I'm talking about, what change wheels might I be looking at.

Hope all this is not too bizarre.

Best, as always, from la belle France.

Martyn

Hello Everyone

I thought those of you who so helpfully contributed to the thread on the dangly probe on my new coaxial indicator might be interested in the denouement.

Jason thought, and I had also come to the view, that the reason it didn't work was a lack of resistance between the slot in the beam and the arm that holds the probe. He suggested the simple expedient of devising a way of increasing the pressure on the clamping screw. But of course, by then I had broken the arm!

So I milled and drilled a thicker replacement arm to create more friction in the slot. I had difficulty machining the 48° wedge shape (cam?) on either side that bears on the slope of the beam and my version is a lot less elegant than the original. But it does work and is made from good steel instead of some kind of 'monkey metal'.

I tested it at 100 rpm on the inside diameter of an Austin Seven piston skirt and got the needle on the indicator dial to quiver around 0.01mm of zero. I don't think I can do much better than that other than send for a Blake!

Bonne Weekend Martyn

ABSOLUTELY BRILLIANT!

Of course, I've broken the arm!

But I did think that when I make the new one I could make it a smidgen wider in the slot on the beam, thus introducing a little bit of friction.

Again, of course, it would have been a much simpler ploy to shorten the retaining screw or introduce a tiny shim, had I not been so stupid as to think the person who put their undecipherable mark on the 'quality assurance chitty' had actually inspected the instrument and it was ready to go! You live and learn.

Thank you all and especially Jason.

Martyn

Thank you everyone for the comments, observations and advice.

I think what I propose should work without the risk of major explosion or conflagration.

I have a Lucas SR4 magneto which originally had a spring metal hoop on the side that you clearly had to press against the body to short matters out and stop the sparks. The person who rebuilt the unit dispensed with the spring metal (very sensibly, in my view) and has left me with a stud, washer and nut which is obviously intended to take a lead, that, I presume, will go to a switch with a connection to earth. Thus, again I presume, the switch will short the magneto to earth in one direction and leave it live in the other direction.

Another instrument I have is a Bosch ZA4 and that has a thin lead coming out of the contact breaker cover, presumably for the same purpose as the set-up on the Lucas SR4.

The magneto I'm concerned with is a BLIC N4R and although it has no external leads at the moment other than those for the sparking plugs, I clearly need to provide something very similar to that on the Bosch.

That said, if the aforementioned lead is connected to the side light terminal on my Lucas ignition/light device and another lead goes to earth, switching from 'off' to 'side', the original side/tail lamp function, should activate and de-activate the magneto....shouldn't it!?

Thanks again for all the valuable input.

Martyn

Hello All

An electrical query if I may.

I'm sure many of you remember the Lucas ignition/light switches that were fitted to many British cars (and a few motor cycles) in the late 30s and 40s. There was a key slot in the centre and then a short Bakelite toggle that moved an annulus with a window to expose the words 'off', 'side', 'head' beneath (the posh version). Alternatively, there was a tiny arrow on the toggle that pointed to the words engraved on an exposed annulus.

Question is, can I wire just the 'side (light)' function at the back of the switch to act as a simple on/off switch for a magneto.

I know I can buy on/off devices from 'the usual suspects', but it seems a waste when I have several of the Lucas type on the shelf doing nowt. But will it work?

Many thanks for your thoughts and best, as always, from la belle France.

Martyn

Very many thanks everybody.

The maths is now clearer.

I think wear on the crankshaft-side dog (not surprisingly) is an issue, apart from the chewing (sic) the tips (points) are worn round unlike the nice sharp ones in the picture.

I also think the initial cutting on a milling machine, rather than sawing them, as I did, is acceptable. But I like the idea of finessing the shape carefully with a Dremel.

Tanks again.

Martyn

Howard/Nick

Can see quite clearly now that the Howard route is the way to go.

I have been studying all the comments and photos and have now mastered the rotary table as never before. I find I can divide a degree to minutes. I'm still a bit baffled by the six division vernier scale! But that's really no 'big deal' as we seem to agree the Vertex is not up to doing seconds anyway.

Many, many thanks. Will try to post pics of the coupling when I get there.

Martyn

I've got a Vertex rotary table. I think it's a V4 model. I've only ever used it to make incremental cuts (e.g. bolt circles) which is, admittedly, very easy using the main degree scale of the table and has been totally successful.

I'd now like to move the table through minutes and seconds ( to be precise 19° 3' and 12". I can't work out how to do this. Could someone please talk me through it in a Pooh-Bear-of-Little-Brain-speak?

Apart from the main 360° scale on the table I have 120 divisions behind the hand wheel (two hours?) and then six divisions on the inner scale (tenths of one minute?). So...wind on 0-19° on the main scale...then what...?

Also, could I ask, what is the pin/lever about an inch long that screws into the second scale ring for? All I can see that moving it ever does is reverse the direction of the table when you turn the handle (if you hold said lever it over!)

Sorry to be so basic. But guidance would be much appreciated and, as always, thanks in advance.

Best wishes and keep safe.

Martyn