Microns ...

On Tuesday and Wednesday this week, I attended mmc2019

**LINK** ... https://www.mmc-series.org.uk/

Amongst the incomprehensible exotica on display, there were some items of 'engineering' interest.

Here are a couple of photos dedicated to the fond memory of John Stevenson; who strived to convince us that it was impractical to work to microns:

A fairly standard optical microscope, retro-fitted with Marzhauser mechanical stages:

The XY stage [controlled by the joystick] is good

But the Z-axis is very good !

Yes ... that display is reading nanometres, and Yes, it is justifiable !

It was the 500 micron version ... Check the spec.

**LINK**

https://www.marzhauser.com/en/products/motorized-focus-drives/piezo-z-stage.html

MichaelG.

.

Edit: In John's absence ... incredulous comment is welcome from anyone.

Edited By Michael Gilligan on 04/07/2019 23:45:32

Michael,

Very nice I am sure and a fantastic piece of kit but I am with John on this one and such an instrument for what I do has no place in my shed lol.

Building a half size version of an early 1900's traction engine and following the prototype where limits and fits were to the closest 5 thou or 1/16" on the cast gears I have no need or desire to work to the tolerances capable of being measured by this!

A common mistake by new builders of steam engines is to make everything to too close a fit and consequently they are so tight they won't run! I have a 5" gauge loco built by an early mentor of mine now long sadly gone which is now 58 years old, on its 3rd boiler and has done 1000's of real miles over the years giving rides on a portable track. Apart from the boiler replacements it has had one set of piston valves and a couple of bushes in the motion to my knowledge and that's it. Yes it clanks and bangs a bit (as does a full size if you get the chance to ride one) but it still goes like the proverbial rocket and I consider it now properly run in. Everything on it was measured with an old manual Moore and Wright vernier and I think it's service record shows that was plenty good enough.

Dont get me wrong, as a time served fitter turner I can make things fit adequately for purpose but I am not going to spend time working to limits that are not required for a decent practical end result. Half a thou is as small as I practically need to measure.

Paul.

No issue with that at all, Paul

It was acknowledged in my subtitle.

MichaelG.

Would it not be displaying 242,107 if it were reading in Nanometers, as I see it the display is in microns to 3 decimal places

I suppose you have to be careful how much you move x, y & z as you could soon heat up the machine and all the callibration would go to pot with the heat from the motors that move the axis.

Yes dear

The display is calibrated/scaled in microns ... but it is still reading nanometres [as the third decimal place]

MichaelG.

Edited By Michael Gilligan on 05/07/2019 07:54:28

Hi, I agree with Michael. This should make it a bit more understandable **LINK** It's just like saying 245.107 inches is 245107 Thou.

Regards Nick.

I suppose it all depends on what you are doing. In my day job, before retiring, I would regularly measure the thickness of thin films to plus or minus a couple of nanometres. I needed this degree of precision to make sure that the films were fit for purpose.

As far as model engineering is concerned 0.5 thou is as good as it gets as far as I am concerned. For most jobs, a couple of thou would be nearer the truth! Horses for courses.

Andrew.

That all seems a bit agricultural to me.

I have just made a bolt for my 1 5000 scale engine that I am building on my 1902 Drummond lathe.

The bolt measures 57 nanometers in diameter and is accurate to 5 picons (can I call them that?)

I am happy to send it for inspection.

Regards.

David.

Sorry I have just sneezed and it seems to have jumped out of tolerance and floated out into the garden.

David.

I thought that was what Michael was saying

If I read that I would say it is displaying 245 point 107 microns. the um after the number is a big clue

Michael is saying it displays 245,107 nanometers. Which I would say should be displayed as 245107 nm

I'm sure if it had been the other way round the pedant in Michael would have been the first to point it out.

Edited By JasonB on 05/07/2019 09:37:20

.

Oh no he isn't !!

Michael showed a display of microns to three decimal places

... and commented that it was reading nanometres

MichaelG.

I'm lost. Please can you press the button that converts it to imperial.

Hi, I think the point is that it has a resolution of 1 nanometre. That's 10000 times better than my Lab scales that have a resolution of 10 micrograms and I've just weighed a piece of Brass swarf about half the size of a pin head and it came to 5.5 mg, or 5500 nanograms if you like.

Regards Nick.

Edited By Nicholas Farr on 05/07/2019 10:25:38

Hi Bazle, about 0.0096 inches. The readout having a resolution of 0,00000003937 inches

Regards Nick.

Edited By Nicholas Farr on 05/07/2019 11:04:46

Horses for courses!

If that level of precision / resolution is necessary, suitable equipment can be supplied / made. BUT at a price, and in an environment which is controlled equally closely, and expensively.

In our non temperature and humidity controlled workshops, working with our "commercial" tools, machines and measuring equipment, John was correct. We can get micron fits, by lapping, perhaps, but not accurately measureable, or repeatable, in most cases.

Working to tighter than necessary tolerances adds cost but little benefit.

The Great Western Railway worked to much closer tolerances than any other UK mainline railway. Their loocos outperformed others in term of economy and durability for many years. But one of the rebuilds of King George V , in preservation, was too precise, and ran a hot box soon after leaving Paddington on an excursion train.

The fit needs to suit the application and its environment.

It was said that in the development of the atom bomb, a naval gun was to be used to bring the uranium plugs together almost instantaneously to exceed the critical mass. A naval gunnery expert criticised the process, as the muzzle velocity would be so high that the barrel would only survive two firings. He was unaware that after the first, it would have been vapourised!

Howard

Well, I'm impressed. Working to a thou or tenths may be all that's needed for most mechanical engineering, but that's child's play compared with what manufacturing does today. While grandad moans about modern youth not understanding tape-measures, chip makers are fabricating reliably in the low nanometre range. Buy a new computer today and it will likely contain a 14nm processor. It might even contain a next generation 10nm chip, but such is the rate of development that 7 and 5nm will be commonplace in 5 years time. There are 25400 nm in a thou.

Even though much of it is obsolescent you might find extraordinary high precision mechanics in the same computer. Rather inexpensive DVD and hard-drives are both built to specifications well beyond anything that could be made in a home workshop. Whilst HSS on an Imperial Myford has it's place, leading edge manufacturing is a century beyond that. Amazing what's done with optical and other micro-technologies.

If you fancy a challenge try making the mechanical parts of a CD-Player from bar stock!

Dave

As we know the first successful Atom Bomb was made in the USA. It's 'quite interesting' to look at what everyone else was doing in the early years. HG Wells' 1913 novel 'The World Set Free' described Atom Bombs 30 years before any understanding of how to make one. The first patent for an Atom Bomb is owned by the British Admiralty, and the first determined build project was a joint Canadian/British endeavour (Tube Alloys) . At about the same time, the military possibilities were being looked at more-or-less seriously in at least Italy, Germany, France, the USA, and Japan. Obvious to all that development was going to be very expensive.

The story is that the physicist seeking massive funding from the Japanese War Ministry explained to a non-technical Colonel that a lump of metal about the size of a hand-grenade would destroy an entire city. Funding refused because the Colonel couldn't see any advantage in soldiers throwing hand-grenades that powerful...

Dave

I suppose it would do for bricklaying and carpentry

Mike

Mike You forgot dressmaking

Roy 

Edited By roy entwistle on 05/07/2019 11:46:53