Member postings for Martin Dowing

That depends, what they were machining.

Even with Plutonium 239 I am not aware of anyone dead due to radiation poisoning nor exposure traceable cancer.

Plutonium-239 is 200 000 times more radioactive than uranium btw.

Energy of alpha radiation is in range few MeV, very much like in case of Uranium and half life is 200 000 times shorter than uranium. Both do not posess gamma radiation associated hazards.

You really have to work with something short living to expose yourself to severe radiation hazards. Examples are Polonium-210 (half life less than half a year), radium (1600 years), Plutonium 238 (half life 89 years, this isotope is useful in spaceship batteries but useless for weapons) or fission products (hazardous waste requiring long term storage has half life between few and a hundred years or so).

Very short living materials like I-131 even if extremely dangerous, decay fast and doesn't pose risk for long.

I believe, the most dangerous radioactive material processed in large quantities is said Pu 238 used for spacecraft batteries. Such batteries could contain few hundreds of grams of Pu-238 each. Anyone absorbing 10ug (10^-5 gram) would be dead like a dodo within months to a year, very much like Radium Girls of the past. Radium girls could absorb 0.1 - 1 miligrams radium each...

hope this helps,

Martin

Martin

Edited By Martin Dowing on 12/09/2017 21:51:46

These days everything is highly toxic, carcinogenic etc, that is one of reasons why manufacturing industry have left UK and moved to China and it will stay that way.

Ever worked with stainless steel?

Read how dangerous chromium or nickel are (both highly toxic and cancerogenic). OK they dont get airborne easily while machining.

Ever used hard solder with cadmium? Awful... cancer guaranteed and you are dead man walking.

It is important to realize that discussed materials are presenting mainly *occupational* hazard and an odd contact with them won't do much harm, if any.

Also if you consider Lead to be radioactive (presumably due to minute quantities of Pb-210 present in freshly mined lead), then potassium fertilizer used in gardening is even more radioactive (K-40).

It is interesting that Lead recovered 500 and more years after smelting is no longer measurably radioactive and finds uses in nuclear research. Hence lead recovered from sunk medieval ships can be very expensive. High price makes diving for it a business proposal.

Fire hazards during machining uranium are real however. Normally such a process is done under argon.

It is difficult to extingush burning Uranium. Water or CO2 is out of question. I would use powdered kitchen salt. As per radioactivity of it, it has too long half life (in excess of 4.4 billion years for main isotope, second one has also close to billion years half life) to be of concern. Uranium ores are more radioactive and dangerous due to presence small quantities of other much more radioactive elements.

I suspect that any issues related to DU radioactivity on the battlefield, if accurate, have probably appeared because it was reprocessed reactor waste uranium, perhaps contaminated with fission products, what was actually used, even if not officially acknowledged.

Virgin uranium (not used before as reactor fuel) is only very slightly radioactive and would not be a source of radiation related health hazards.

Chemical toxicity is comparable to lead, eg not very great unless you are occupationally exposed for years.

Needless to say, it would be daft and outright stupid to attempt to work with uranium at home workshop or even only to try to acquire uranium metal.

You don't wont to spend rest of your life being observed/bulshited by beaurocrats of all sorts and possibly open yourself to legal challenges which you don't understand.

Go on and turn Platinum or gold with few % iridium alloy (which is hard, turns well and used in dentistry). It is as dense as tungsten.

Densest elements are Osmium and Iridium, machinable by grinding mainly.

I have commented on wide change of prices noted by previous poster, not on items like *handwheel for $ 1000 or so".

Regadring shortages of stuff.

It is our foolhardy assumption that most inteligent nations on Earth like Chinese or Koreans are going indefinitely to produce "stuff" for us and accept payments with funny money generated out of thin air as need arise.

At some point they will demand payments in harder assets, the terms we cannot meet.

Then prices of Chinese crap will skyrocket and due to lack of domestic manufacturing base (which got legislated out and outsourced) Europeans will not be able to afford even panties.

As I have said, our economy is just a hot air.

@SilyOldDuffer,

Tactics which you have noticed is one of many symptoms of far wider disease of Western economies in general.

There is less and less to sell and more and more hot air blown in. No substance, no manufacturing anymore, just rules & regulations forcing us to do nothing and more debt everywhere. Fraud out of plain necessity becomes about the only viable business model, at least for larger entities.

It is no longer economy, it is just pretense which is going to blow up and lots of hardship and pain will follow.

All is OK with reasoning above, but I bet that an odd fool sometimes *does* pay.

No, it cannot be.

About 2/3 inch is threaded from one side of pipe but there is taper on entire lenght of pipe, threaded or not.

Tapered threads are not this long anyway and taper is steeper.

From second side (one which srews into base of oiler) only few turns are made with the same thread and thread doesn't look tapered.

Hi,

The thread is from an end of brass pipe screwed to the base of RDG oiler for ML7. This pipe with small holes nearly bottom, oil pass down through these holes down to sight tube.

Unfortunately it is impossible to tell, is it 55 or 60 deg, because it is (like many other items from RDG) quite badly formed. Angle seems to be somewhere between, flanks of thread are torn while new and pipe has taper 4 thou per INCH.

So weighing all evidence, it is probably 1/16" BSP.

NB. Poor engineers from old Myford are turning in their graves or getting very upset in their old age seeing so badly made stuff sold under this brand.

I have measured thread of a bolt for which I will need to fabricate nut, so it will be necessary to purchase appropriate tap for this job.

So OD is 0.3" (7.64mm) and 28TPI.

I have failed to find such a thread in my reference booklet.

It that a standard thread (and if so, what it is) or perhaps something weird, non standard?

Hi,

I am now in the process of doing very much the same (rebuilding or rather improving precision) of old ML 7.

1. Spindle bearing. This one usually need scraping in.

When I got my replacement set, I still have bought new set from Myford Nothingham.

I was advised that the set is carefully made and and it is unlikely that futher scraping will be needed once installed. All what I had to do is to sdjust shims.

I was recently wiggling test bar homed in socket and there was no more than 0.5 thou of DTI movement as checked on side of spindle register.

That is very good.

2. Leveling.

Precision level with accuracy better than 1 thou per foot (0.05mm/m) was used across bedways at headstock and tailstock. This is a bit overkill, lower grade level, say 3 thou per foot is good enough but I only have much better one.

Leveling was done up to 1 thou per foot accuracy. A lot of piddling here...

3. Headstock allignement.

Once lathe got levelled I have done a turning test on it,

Decent 1 1/2 inch diameter MS bar with 2 bobins od 2 inch diameter F/C steel spaced 6 inch was installed on 4 jaw chuck, centered properly and turning test was done and measurements taken

Unfortunately that was much off, something like 8-9 thou a foot off!

This sad state of affairs had a long legacy. When I have bought my lathe, it was worn. Bedways, saddle and tailstock base were rescraped by professional but dmaged spindle bearings was left as they were because I didnt have a new set yet. Hence said professional couldnt allign a headstock and now I had to do it. I had to reallign machine once new bearings and spindle have been fitted.

Fortunately it was not as difficult as many legends are stating.

So 4 high tensile strenght screws bolting down head to bedways were loosened.

No, usual Allen key wont do it, had to buy a proper one with a socket.

Then 2 screws pressing headstock to a shear was losened and I hoped to be able to move the headstock but I couldn't.

Some moron, sorry, pevious owner, filled everything with paint. I had to use (carefully) some lever to disassemble "paint welded" headstock.

All the paint was now cleared from vital surfaces.

There is some play between headstock and shear, allowing for a tiny twist.

Adequate shimming was inserted from rear side and headstock was bolted back. before final tightening 2 screws pressing head against a shear were also tightened.

Some maths is handy here and it helps greatly to calculate thickness of shims before scewing it back. Armed with basic trigonometry I needed to make final adustement only once by *axially* moving already installed shims less than a quarter of inch.

Final accuracy by turning test better than 0.0005 inch a foot.

Not bad... but it is not all.

Now *vertical allignement had to be checked... and turning test is not very good for it (less sensitive).

So I removed test turning bar from the socket and inseted hardened 25mm ground bar used in linear bearings and centered it very well in 4 jaw.

First I reconfirmed horizontal allignement, few times, turning chuck a bit each time to make sure the bar is not bent.

I was really pleased to record better than 0.0005 inch a foot allignement again.

Now I checked vertical allignement by applying DTI from the top.

Oops... head was watching up about 1.5 thou a foot.

This was remedied by loosening bolts like before and inserting shimstock under back of head (trigonometry help here, first attempt was the last...

All described drill were repeated, final outcome was better than +0.0005 inch a foot horizontally and no measurable deviation with my dti vertically.

But what about facing?

To check error there I needed a decent *flat* faceplate... and all of mine are concave with concavity exactly like my lathe produces.

So I grabbed one and gave it to professional guy on surface grinder... and he ground it flat.

I have installed it on my machine and checked with DTI for "wobbling". It seems that professional guy done his job right as it didnt "wobble".

Now I have run DTI across. Just below 1 thou a foot. Thanks God... Crosslide/saddle alignement is good enough.

Unfortunately this is not all... You remember I was using hardened 25mm linear bearing bar held in 4 jaw for allignement testing. Meantime I have ordered one to use with Morse socket and it came.

And guess what... once installed it wiggles about 4-5 thou per foot of lenght. I started to look on this test bar with utmost suspicion, after all it came from RDG... However centered in 4 jaw it shows very good allignement like my previous test bar did. Unfortunately 12mm hardened linear bearing bar held in 12mm hardly used original Myford collet also shows bad runout.

It seems that taper need regrind. Now I am making substantial cross slide mountable holder of my machine mountable internal grinder. It is Milwaukee tool and can rotate up to 30000rpm. My ML7 has taper turning attachement so I should succeed.

I intend to but hardened *master MK2 male taper* to accurately allign everything befor this tiny 0.2 thou cut, grind few sockets to make sure I have learned to do it right and then fingers cross and hope for the best...

I will probably ask few question before I actually do it but I welcome any suggestions now.

Also who sells this *MK2 male master taper* with reasonable price?

Yes.

This "wide guide conversion" is a good idea and quite often discussed.

Presumably regular gib strip in front side of saddle need to be shaved a bit to widen gap on the back. Probably unused shear will need scraping to provide better bearing surface. What do you think about it?

Anyway at the moment my lathe doesn't need it albeit I do wonder if doing so would allow me to get rid of a little bit of stifness noticed while carriage is winded down to tailstock.

Edited By Martin Dowing on 06/09/2017 23:24:22

I have turned 8 tees from a round bar on my ML7.

4 was done in C45 (EN8?) and another 4 in increased tensile strenght stainless.

22mm round bars were used

Then, using vertical slide, I have milled shoulders. Then M8 threads were cut with die and ready parts were chopped off chucking bits

So there was NO drilling holes, tapping or brazing, but still much more work.

Drawbacks: 2 days wasted.

Advantages: they seem undestructable.

63 tooth gear gives rather poor accuracy in metric/imperial translations.

There are far better combinations than that with standard gears of 20-21-25-30...75 teeth.

For superb accuracy you will also need 38 and 42T.

127T gear even if perfect is rather impractical (too large).

Read "Screwcutting in the Lathe" by Martin Cleeve.

You will find nearly everything you need to know (and more) there.

@Lambton,

Yes, I did. This 1 thou is what you get this way.

With some force applied (within reason) it will go 1 1/2 thou but then spring back to 1 thou.

@ Neil Wyatt

The nice thing with flat bed is, that even amateur with moderately advanced skills could scrap it back to shape once need arisen.

But of course it is better if there is no call for it at the first place.

Thanks for your comments.

As I have written, lathe is cutting clean, so no alarm yet but It is nice to know that situation is "very acceptable".

I just wondered how much "wiggling" is acceptable in industry, if machine is to be considered "precision".

I have seen big lathes where saddle was wiggling like a drunk man walking on the curb and still operated.

I was testing my ML 7 with a test bar and DTI

I have noticed that when I change direction of saddle travel there is about 1 thou "jump" on DTI reading, as if saddle "wiggles" slightly when dragged by a leadscrew right and left. Gib strips are adjusted

Of course more "jump" is close to headstock.

How much of such "jump " is acceptable before some bedways correction is called upon?

At the moment lathe is cutting clean, no chatter etc.

Edited By Martin Dowing on 04/09/2017 08:14:12

I have bought these RDG oilers.

They are a nuisance but got them working.

1. The sliding lid closing filling hole on the top is not good. Seal is not there and grit from workshop can penetrate inside. So the spring loaded closure from old broken oiler was soldered in to remedy nuisance.

2. Felt rings were made and installed on the pipe with hole at the bottom (oil pass through this hole from reservoir).

They act as oil filters and are important, if you don't want to have unnecessary problems with bearings.

3. For some reason oil was not dripping but flowing on the wall of short section of the sight tube. To remedy that rubber seal was replaced by identical one made of Teflon, punched from 0.5mm PTFE plate (carefully applied plumber sealing tape will also do). It repells oil (cannot be wetted with it, preventing capillary forces from drawing it sideways) and now oil drips, not leak along the wall of plastic sight tube as it was in original design.

4. Needle valve locking flow of oil was good as purchased. For now it doesnt leak and slow flow 1 drop per 1-2 minutes can be established. Actually if that was not good either, I would trow entire thing away. It is ahame that engineering company cannot design working oiler and I had to piddle a lot to re-engineer it to standard.

And it would not be even more expensive to make it right at the first place.

@Hopper,

Yes , it was done by professional fitter 12 years ago.

He advised me that job on bedways, saddle and tailstock would be done but bearings are in such a poor state that I really need to replace them.

Actually I did not need a fitter to find it out - spindle was "wiggling" under pressure. So he has advised me that headstock would be left as it is and I need to keep fingers crossed and hope for the best and with some bed twisting it might be acceptable if not perfect.

However I have been warned that I might need to allign a headstock once bearings are changed. In his opinion for ML7 it is rather trivial, so I should cope. As I have said it was long time ago and contact is lost.

BTW, by principles it seems trivial, but I try to gather knowledge how to do it the coorect way and find out about any tricks there, just to save myself fiddling and piddling for a week, before arriving at correct setup by chance.

Regarding bearings.

Now I live in quite secluded area (and a country) which is really beautiful and charming but entirely devoid of peoples capable to do bearing scraping or most of other industry and I am not yet up to the task myself.

Such a job could certainly make them a bit better but up to date observations are not revealing obvious troubles from this source.

So I would either need to take machine 200 miles to outlet which does it (tedious) or pay for them to delegate worker to me or find a fitter and fund him a week of holliday in my place and meantime job would be done (I have terminated my professional careeer in chemistry and now run small hotel for a living).

@ john,

Many thanks for your comments. These are valuable.

Regarding my bearings.

These *are* phosphor bronze bearings working with hardened spindle. They were not scraped in, however I have bought them new as a set in old Myford works , in Beeston nearly Nottingham in 2004.

Peoples there have advised me that they have made certain rectification of manufacturing process and as per their belief it is unlikely that I would need to do hand scraping before bearing adjustment due to wear is needed.

Lathe had some rather light use but recently, during last year or two it is used more (interest in precision mechanics grows with age and it seems to be inversely proportionate to interest in women :D ).

Bearing surface was inspected occasionally at the time of belt change and pulley slipping trouble and nice shiny contact areas have developed, may be not as nice as those in properly scraped bearings but still reassuringly large.

There *is* some resistance of a spindle when I attempt to hand turn it by pulling a chuck. After a moment system gives in and begin to turn. No "double cuts", unless initial one was rather heavy or even more so if heavy and done with slender boring bar.

Bedways and saddle scraped by professional fitter to bring machine to its former glory.

Btw, this 7/32" Allen spanner to undo head bolts already ordered and guess, it will come with 3/8" square socket. One with 1/2" square socket would be too clumsy.

Regarding horizontal and vertical misallinement.

It seems that first is the one to look for and second must be catastrophic to matter, unless very small diameters are turned.

For 1 inch diameter horizontal misallinement of 10 thou per foot would give 20 thou total taper over said foot of distance.

With vertical misallignement of the same magnitude on 1 inch bar error would be 2 x  0.0000999 of thou (say two tenths of thou of total taper over foot).

On 0,1 " diameter error would grow to 2 x 0.99 thou, say 2 thou per foot total taper, still acceptable. Based on those it seems that in normal work undertaken by model engineer vertical misallignement matters little, but those attempting to turn a hair a bit could really fret aboit it - they could end up turning nothing at all.

Martin

Edited By Martin Dowing on 04/12/2016 20:32:55

@Brian,

Well this idea is what I will try with great care, however due to a lack of test bar I will have to rely on bar with 2 bobbins mounted in 4 jaw and used for test turning. Aternatively I have 1in diameter and 20 inch long high precision round grounded, hardened bar which is not bent for sure and this one mounted and centered in 4 jaw may do as replacement for a more usual Morse taper ended test bar.

@Hopper

Bearings are OK. No play really and not long ago parting of 1 inch diameter steel bar 2.5 inches from the end of chuck and without tailstock support went with not much fuss and this indicates good bearings. My understanding of a bearing is that there is about 1/2 thou of oil clearance there, so longer steady pressure would at the end displace this oil and even good bearing would give in this 1/2 a thou or so.

As I have written, my measured misallignement of nearly perfectly levelled lathe is in excess of 9 thou per foot. Bearing fault to deliver that would be substantial, machine would produce a horrible chatter (but my cuts clean) etc.

Also bed twisting can reduce taper to 2 thou per foot, unfortunately taper narrows to tailstock end. However bed twisting has its limits and I got there shiming with 50 thou under far end foot of the tailstock end. IMO it is a cut off. Such a shiming doesn't correctly allign lathe either as certain diameters tend to be turned more paralell than others and at this point it is time to address real issue and not pretend that something is done if it is not.

Headstock allignement done intelligently is the way forward here and I have decided not to approach it as a tabu subject and no go area, as many of us are doing.

Important are details, about procedures used by Myford, as those may save much trouble and effort.

For me it seems certain that such work need to be done with decently levelled lathe to begin with. Precision level is a must here. Later it is a matter of *twisting* headstock until the tapers are within a range of thou per foot or better (Myford works were happy with 3 thou per foot albeit majority of lathes got much better deal than that).

Most what matters then is horizontal misallignement. Vertical one (business end looking up or down) is much less likely and consequences are not as severe, unless substantial.

@not done it yet

It was turning test, not bar in the chuck + dti test

Edited By Martin Dowing on 03/12/2016 21:22:19