Member postings for Tim Stevens

I live on Offa's Road - but the NHS and various other official departments omit the apostrophe. Not what one expects from a government manned by the products of our public schools.

Of course, e-bay misses the apostrophe too, as you might expect.

Cheers, Tim

We are advised that white metal bearings in a Myford will 'tolerate' a bit over 600 rpm, with its drip-feed oilers.

Old car engines with similar oiling systems (a bit more oil mist, but dirty oil) will stand up to 4000 rpm and much higher out-of-balance loads. And much longer periods of continuous loads.

So - could we push our Myfords round rather more quickly?

Regards, Tim

I give the 'correct' spelling for the UK - according to the latest info from the New Scientist.

Cheers - from an old scientist

Tim

See SK at 21/07 ...14:46:50 above - Of course, the invar will extend slightly as the weight of the bob is added to it, but having extended, the mass will remain the same, and the centrifugal variation with a modest swing will be next to buggerall, so the extension should remain almost as nearly constant as gravity.

And - later, different topic: The traditional arrangement of compensation suggested here is to use the invar (eg) from the pivot through the bobweight, then brass tube (eg) up again. This makes the pendulum longer. It seems possible to avoid over-length by having the brass tube upwards from the pivot, the Invar down from there. With this design, the extra length could be hidden by the horse, cuckoo nest, or whatever ornament is added above the dial. And in some clocks could rock a boat. Why not?

Cheers, Tim

Hard Rubber may well be an alternative (? colonial) term for Ebonite - as used for the cases of car batteries until this century. (=/-). Another description is hard vulcanised rubber - in which more sulfur* than usual is used, so the rubber loses its springy nature. The black is carbon.

And a further warning re celluloid - it is only a smidgeon different from nitro-cellulose (gun cotton). So don't hit it. Old cellulose is hard because the plasticiser (? camphor, from memory) slowly evaporates. That is why the coating on pre-war steering wheels is fragile.

* yes, that is the correct modern spelling. It derives from a country where ass doesn't mean donkey.

Regards, Tim

Has anyone considered that the problem 'banjos on commercial fuel filters' might be a lot to do with the design and material used on fuel filters (nothing like brake pressures, of course) rather than the idea of a banjo itself?

Tim

127 is a useful (but prime) number. Useful for english to metric conversions. But difficult to make from scratch and somewhat huge.

Tim

Has anyone every suggested adding a new 'lead-screw' to a lathe by using a wire wrapped around a drum to pull the carriage along (and back)? It would surely easier in a home workshop to make up a few pulleys and a drum or two, rather than making (or buying) an Acme or simliar screw set-up?

Tim

Surely what matters is what the motor is intended to do, in service? A motor for a toy drone is not at all the same thing as a motor for a town-hall clock, or one for a dentists drill, or one for use in a coal mine?

Horses and courses, all that sort of stuff

Tim

Edited By Tim Stevens on 21/08/2023 15:23:01

I would argue with Ady1 that the best start might be with a short (inflexible) drill, rather than a 'big' one. Get the hole properly central throughout and there is less chance of further eccentricity.

And just so you know, I think there is a generous selection of eccentricity in many of the postings, and a good thing too.

Cheers, Tim

I would try Option 4, and use a chain-saw file to clean-up the offending blemish. Once it looked OK, I would silver-solder in a bit of round bar to match - size and colour. Then machine to remove the excess.

The major advantages of using a chain-saw file are that the diameter of the file can be selected from a wide range (from about 1/8 inch to 1/4 or more) to suit the size of the blemish, and to match an off-cut of rod. And being the same diameter throughout, the fit of the newly filed groove should be plenty good enough.

I hope this helps

Cheers, Tim

Another thought: If you need the metal hard, and the bend is gentle, you could try the effect of coining the material. This means that you make both halves of the die of a hardened material (and chunky) and start with a strip of silver slightly thicker than the final product. Then you force the two halves of the die together so that the metal is squeezed to the final shape. A decent large vice would be good for this, or a powerful jack. A big fly-press can also serve, but you have less control over the amount of pressure.

The term coining relates to the way coinage and medals are produced. The metal is forced into every last detail of a hard steel die each side, hardening the metal as it does so. If t he dies are nicely finished, the result should need little further work. Any file marks or emery scratches will show in the silver, so do spend time to ensure the finish of the dies is good, and you will save time finishing the resulting presswork.

Cheers, Tim

I can help, perhaps, from my own experience as a silversmith apprentice. To make sharp corners in a silver box, I cut a groove along the line of the desired bend. The tool was made from a bar of silver steel, heated red and turned over at the end. then filed so that it cut a 90 degree slot when pulled along. And then hardened and stoned to the exact shape. A thick steel rule was clamped firmly to the flat plate, and the tool drawn along by hand several times, to remove about 2/3 of the thickness, along the length of the fold required. The same operation was then done for the other folds in that workpiece. Two parallel grooves, and two more at 90 degrees, gives the base and four sides of a box - and four off-cuts in the corners. These latter pieces were carefully removed and the edges filed smooth at the correct angle. Then the sides were folded up to bring the edges together, and propped on a heatproof slab with the sides held firmly together. Borax flux was then applied, and the joints were silver-soldered to give a smooth, rounded run of solder down each side and along each of the base edges. this resulted in the outer edges of the bottom being sharper than could be achieved by bending, and with no chance of roughness as the thinner metal was indeed bent rather than soldered, on the outside. At the same time, filling the join with solder made it much stronger (firmer) than a simple bend.

For your purposes, the tool (and the grooves) should be made sharper (say 40 or 60 degrees, not 90) to suit the geometry of your bend. But remember that if you need the result to have the stiffness of hard-rolled metal, this process might not be ideal as the soldering will surely anneal it.

I hope this offers a way forward

Cheers, Tim

Spectacularly made? Surely it must come from a bloke who cannot find his glasses?

Tim

SoD says: Art can't be quantified and checked against a specification. That means everybody's opinion of it is of equal value.

I suggest that this depends on how you define ‘value’. In the art trade, the value of an item is what someone will pay for it, so the decisions always depend solely on the views of the well-off. And clearly, the majority – who tend to have little or no spare cash – count for nothing.

Of course, the value of an item can be judged in other ways, but it seems to me that SoD is – just this once – wide of the mark.

Regards - Tim

My local show includes an award for 'Best Overall Display'.

All I need is a tailors dummy or two and I could show a wide range of overalls. What are my chances, do you think?

Cheers, Tim

If you are going to use a dead centre for this sort of push-location, use a small rolling bearing over the end of the tailstock centre, with a thick washer resting against the work. Much less heat will be generated, and much less wear on the centre etc. A thrust bearing would be best, but a conventional ball-bearing will take end loads for a reasonable time.

Then put the bearing and washer in a matchbox and keep it with your other turning odds and ends, ready for next time.

Cheers, Tim

Edited By Tim Stevens on 16/07/2023 10:55:20

The comparison - early in this series of messages - with cooking oil is not helpful or even relevant. Cooking oil is vegetable or animal in origin, but mineral oil is, well, mineral. That means it has been hanging around on the earth for millions of years, and anything which will go off in a year or two has gone.

Cheers, Tim

In any question of 'what is this critter?' it is hugely helpful if we are told which country is involved.

Trying to find a japanese moth in an austrian moth book is never easy.

Just a reminder - Cheers, Tim

You could use the term 'frequency' instead of Amplitude. But I suspect that there is a good reason not to. Using 'terms of the trade' rather than everyday expressions is a well known dodge in a wide range of trades and professions. It ensures a degree of aloofness - and I'm sure you realise that other terms are used for that, too.

Regards - Tim