Member postings for David Littlewood

Harold,

I drew David C's attention to this problem last month; see: **LINK**

David

John,

You are putting words in my mouth instead of looking carefully at what I said. I agree - and never said otherwise - that PTFE has a very low coefficient of friction, both with itself and with metals; I also said it would lubricate as long as it stayed on the metal. What it will not do is bond to the metal and form a long-lasting coating; it will stay in place only as long as its carrier liquid keeps it there None of the references you cited say anything to counter this. Yes indeed, it is possible to bond the polymer to steel, but only by activating it with same fairly hairy reactive compounds. Nothing which would be put in a spray for public use comes close to this level of reactivity. See for example **LINK**

In any case, the question was about rust prevention, not lubrication - not that this discussion is not of interest!

David

Chris,

You might find this book quite a useful introduction to most of the materials of use to model engineers, including the commonly used steel grades: **LINK**

David

Teflon is a solid polymer plastic, and when used as a lubricant as in these sprays is present in minute particles. One of its main qualities is not sticking to anything, so it is hard to imagine how it "forms a coating" to protect surfaces. In reality the solid particles will lubricate with moderate effectiveness just as long as the sticky carrier gums it in place, and not a moment longer. If you want something which bonds to the metal surface and forms a long-lasting lubricating layer you need a formula containing molybdenum disulphide or similar.

David

The OP was asking about hand tools kept in a bag, and was presumably concerned about rust-proofing, not lubrication.

David

Like I said right up at the top - Shell Ensis.

David

I always thought WD-40 was a teflon spray; certainly several of the similar sprays I have used over the years have been.

However, WD-40* is crap at rust proofing (and most other things; not bad for driving water off ignition leads, which is what (IIRC) it was first made for). Teflon is a low-friction polymer, and also has zero rust-proofing qualities. Tell him to wipe them with Ensis rust proofing oil instead.

David

Hansrudolf,

You are right - I was thrown by the length and pitch being the wrong way round, and the use of decimal points without a following .0

David

Garry,

Best of luck finding those! I've never seen any, though there are several ranges of ISO metric fine threads which does include M10.0 x 0.5. However, to help others to help you, could I suggest you (a) confirm the exact size you are looking for - you decimal points are in odd places - did you mean M10.0 x 0.5mm? and what was the 0.75? if it's a length, it's a bloody short screw! And (b), what is it for? someone may have some alternative suggestions.

David

Michael - not me, unless I did it in my sleep sometime!

David

Listened to an interesting programme on ammunition on Radio 4 last night (which they most annoyingly insisted on referring to as "bullets". It was suggested that the switch to 5.56 mm was made in cold war days, in anticipation of a European war with lots of close fighting and for which a range of 3-400 m would be fine. This was proving to be quite unsuitable for an Afghanistan-type conflict, and they were having to take 7.62 mm machine guns and rifles out of store to be able to engage, with some hope of accuracy, at long ranges.

If you missed it, you can hear the programme (for the next week) on the Radio 4 listen again facility. Some interesting stuff about making the ammunition.

David

Edited By David Littlewood on 29/08/2012 11:35:31

Clive,

Sorry, I misread your post - you said recoil, I read muzzle energy; my fault.

David

Swarf,

I second Norman's recommendation of the GHT book - it has to have been one of the strongest influences on my work, and I'm sure many other self-taught machinists. His little recipe for a topslide lock (only about half a page and a photo) is worth the price alone!

David

Edited By David Littlewood on 28/08/2012 18:14:37

Clive,

I'm sure you - and a lot of keen pistol shots - could achieve that kind of accuracy, but the military people who probably only got to fire a few shots in training, if that, would have found it very much more difficult to hit anything.

PS - I think you mean the muzzle energy of the .44 Mag is 1200 ft.lbs - 12 is the legal limit for air rifles! Certainly 1200 is the figure I have in my memory. I gather quite a few in the USA like long range target shooting with 0.5" BMG rifles at 12,000 ft lbs - now that's what you call a stopper.

David

Andy,

I think it was a WW2 general who said most soldiers he had known couldn't hit the sea from an open boat with a handgun. I recall another said that, in all his long military career, he had only known of 2 people hit by shots from handguns, and they were both on the same side as the shooter.

David

Neil,

SCAYT?

I think glycerin is the German spelling. Everyone knows that people in the USA can't spell for toffee anyway.

Potassium permanganate is readily available on eBay and elsewhere; it is frequently used for staining wood. It used to be used for treatment of athlete's foot, may still be for all I know.

David

Clive,

AIUI, the propellant is mostly nitro-cellulose (guncotton), though some recipes may nitroglycerine and other additives such as nitroguanidine. (Actually, for the terminally geeky, "nitroglycerine" isn't actually nitroglycerine either, it's glyceryl trinitrate - nitro compounds have a C-NO2 structure, whereas nitrate esters have a C-O-NO2 structure). However, it is probably toxic in the same way; IIRC most organic nitrates are powerful vasodilators.

And yes, I also had to hand in my pistol - only in ~1998, as I only had a .22 Hammerli. Still miss it, though I was never a very good pistol shot, preferred the rifle.

David

Edited By David Littlewood on 27/08/2012 23:31:23

Aidan,

I installed a Sino system from Machine-DRO to my Emco FB2 a few years ago. The installation was fairly painless, the instructions were helpful, and the company themselves were helpful when I needed to ahve something changed. Sorry you didn't get a reply from them, maybe something went awry or it was holiday period. I do recall having a chat with the Machine-DRO chaps at an exhibition, and they did seem quite helpful; maybe you could try that.

A year or so after these pictures I also fitted a Z-axis scale; this involved slightly more fiddling around with brackets to get both ends of the scale fixed to the column, but it was fiddling rather than difficult. The installation has worked flawlessly for me since installation. Here are some pictures:

I know there have been some articles in MEW about installing scales to various machines, but more often lathes rather than mills; I suspect this is because installation to milling tables is usually quite straightforward. What I would say is that the fitting of the DRO transformed the precision I could routinely (i.e. without very tedious exceptional measures) achieve in milling and drilling, and I would not be without it. I would say, don't let yourself be seduced by cut-price bodges with digital calipers or scales, go for the quality stuff; the pleasure is enjoyed long after the pain of paying is forgotten.

David

Edited By David Littlewood on 27/08/2012 13:06:34

Raymond,

I really must give you my warmest thanks for pointing me to that blog. As a D Phil organic chemist it probably appealed to me more than it would the average reader, but it just had me howling with laughter for over an hour. My wife must have wondered WTF... Brought back a few memories of near misses too!

Rather annoyingly, the thing would sudddenly freeze and then (after a delay) shift to an error page after a few minutes; pressing the back button went back OK, but it made the reading a little laborious.

David

Clive,

That makes sense; the two acids would react to form chlorine gas, only slightly soluble in water. Also highly corrosive and damaging to lungs - used as a poison gas in WW1 of course.

David