Wikipedia:Reference desk/Archives/Science/2017 July 23

= July 23 =

Judgement of "healthy" and "sick"
If someone gets an infection and shows visible signs of illness, then it is obvious that the person is sick and requires treatment/cure. But having a pathogen is not so clear-cut. The pathogen may hide within the body and can manifest when the person's immune system weakens or when a person unconsciously spreads it to someone else. If a person catches a pathogen and the pathogen is strong enough or the immune system is weak enough, the person will get sick. But if the pathogen just hides in the body (chicken pox/shingles), then is this person sick or well? Also, what about chronic diseases? One may have an excessive amount of body fat and statistically would be more likely to have obesity-related diseases. But if that person eats many fruits and vegetables and does vigorous physical activity regularly and has no signs of chronic disease, then is that person healthy or is the increased risk for an illness enough to qualify as sickness? 50.4.236.254 (talk) 01:54, 23 July 2017 (UTC)
 * Your name is not Mary by any chance is it? 110.22.20.252 (talk) 06:04, 23 July 2017 (UTC)


 * We all carry many pathogens, some active and some dormant. I would use adjectives such as "infected" and "overweight" rather than "sick" or "ill" for such situations.    D b f i r s   06:41, 23 July 2017 (UTC)


 * Check the origin of "sick" and it's reasonably clear that it means someone who has symptoms, i.e. has been "weakened" by whatever ails him. ←Baseball Bugs What's up, Doc? carrots→ 07:25, 23 July 2017 (UTC)


 * They'll probably have signs as well as symptoms. Richard Avery (talk) 07:58, 23 July 2017 (UTC)

An interesting article for this is Endogenous retrovirus; see also. There are actually a handful of sequences that humans require to be healthy which are based on pathogens. Wnt (talk) 16:08, 23 July 2017 (UTC)


 * scores of thesis and books (i mean, serious books made by people teaching in university) have been written about this subject, with historic, ethnographic scope, and environmental so don't expect any straight answer. Social definition of the normal (including healthy/ill) change in place and time.
 * You know the sentence "it's not a bug, it's a feature"? Well, in biology/medecine you have the same thing happening. Sickle-cell disease is another example of the difficulty: it is either just a disease or an adaptation depending on whether malaria is controlled or endemic.
 * Gem fr (talk) 08:56, 25 July 2017 (UTC)

drilling and reaming
I'm trying fit a 1.5mm dowel pin into a piece of brass. My current plan is to:

1. Drill a 1.45mm undersized hole

2. Ream it to 1.5mm with a 1.5mm reamer

My question are:

Is the 1.45mm undersized hole really necessary? Or should I start with a 1.5mm hole right away?

Is the reaming step necessary? Would a 1.5mm drilled hole still be able to achieve an interference fit with a 1.5mm dowel pin?

Should I use HSS or carbide for drilling and reaming brass? Covfefe beans (talk) 05:36, 23 July 2017 (UTC)

Looking at the reamers, some are advertised for hand tool use, and some for machine tool use. What's the difference? The machine tool ones are significantly cheaper.

Would I still able to jerry rig a machine tool one for hand tool use? I'm only making ten holes with hand tools for hobby usage, so I can't really justify paying 5 times the price for the hand tool ones. Covfefe beans (talk) 05:41, 23 July 2017 (UTC)


 * Since you haven't specified what the use is, it is impossible to answer your main question, but a 1.5 drill will produce an oversize hole. As to machine reamers as opposed to hand ones, I suspect but do not know that the hand reamer will have a more progressive lead-in taper. At that size yes you will probably get away with a machine reamer. If it is too difficult to get houing then grind some more taper on it. Greglocock (talk) 10:21, 23 July 2017 (UTC)
 * I'm trying to mount a 15mm long 1.5mm diameter dowel pin coaxially on a 60 tooth brass gear, and using said dowel pin to drive another rotary mechanism. The gear is 5mm wide, and the hole is through all, so the dowel pin will sit 5mm deep into the gear. Ideally it will be an interference fit so that I won't have bother with glues and stuff. Covfefe beans (talk) 11:34, 23 July 2017 (UTC)


 * Is there a reason you choose not to use Tap and die tools to cut threads on the pins and holes so they can be simply screwed together?
 * A possible tool for your plan is a Dremel power drill with stand. If you begin with a slightly undersized hole, you may
 * Chamfer the edges of pins and holes for easier insertion.
 * Noting that the Thermal expansion coefficient of pure Brass is 19 x 10-6 K-1, freezing a pin may allow it to be pressed into a warm undersized hole.
 * A last resort is to split the end of a pin with a very fine saw so that it can compress to fit the hole. To keep a strong fit you could use Cyanoacrylate or Epoxy adhesive. Blooteuth (talk) 16:26, 23 July 2017 (UTC)
 * Dowel pins are case-hardened steel, so a die won't even scratch it. You'd need a CNC gear grinder to get a thread on there.
 * Though you do bring up a good point. I could go with a M1 or M2 tapped hole, and put a threaded rod or some sort of a headless screw in there. I actually never considered that approach. Covfefe beans (talk) 02:06, 24 July 2017 (UTC)


 * Use your experience to judge the best method. Gain some experience by just trying it, with the accessible tools you have.
 * There's more than one way to do this, the best is often simply that which works, given what you have.
 * A 1.5mm reamer is brittle as anything (and expensive) and must be used in some sort of jig - a vertical drill press or tapping machine, turned by hand but held accurately vertical. Holding it by hand is (IM-clumsy-E) just a way of snapping such thin, brittle reamers. If you must, use a pin vice rather than a (heavier) tap wrench.
 * I would suggest finding some books on clockmaking, or even watchmaking (1950s ones are best, as representing a level of technology that's easily accessible by a hobbyist today, 60 years on). They'll discuss plenty of ways to put an axle into a wheel, attach it firmly, then true it afterwards. This seems a far more achievable goal than trying to make a perfect hole, then have a pin fit into it perfectly, by the Power of Optimism.
 * Another approach to achieving impossible standards is to find a reason why it's not needed. Redesign the mechanism such that it's less critical for perfect alignment. Using a larger pin, or a pin with a larger mounting boss, or a flat-face flange against the face of the disc, could all be useful approaches. Andy Dingley (talk) 20:40, 23 July 2017 (UTC)


 * A rollpin is a better choice than a dowel. I think you'll find clock makers often used tapered pins for this job. The reamer for a tapered hole will probably cost more than a cylindrical one. It is possible to make your own finishing reamers, called D-bits in our workshop. basically take a steel rod, turn it to the desired shape, and then grind half of it away. Then harden it and you have a single flute reamer. It is accurate but not much use for anything other than final sizing. Greglocock (talk) 20:48, 23 July 2017 (UTC)

North Korea fissile material
Where does North Korea currently get its fissile material? According to North Korea and weapons of mass destruction, it could be at the 5MWe reactor at Yongbyon or at the spent fuel reprocessing facilities (also part of Yongbyon?). The same article says that NK has 6 to 10 plutonium warheads or 13 to 30 nuclear equivalents for plutonium and uranium stockpiles.

Where does NK produce fissile material? Have the North Koreans ever built a nuclear warhead? If so, where? --RoyGoldsmith (talk) 21:38, 23 July 2017 (UTC)
 * "Have the North Koreans ever built a nuclear warhead? If so, where?" They've built at least 5. One was around 10-30 kT TNT equivalent. Yongbyon is the most likely assembly facility. it is a moot point as to whether any of these devices were physically small enough to be a warhead. Greglocock (talk)
 * Do you have any sources? As near as I can tell, your statement about (1) five warheads with one 10-30 kT and (2) Yongbyon being the most likely factory isn't mentioned in the article. If we have reliable sources, we ought to modify it.
 * Also, where does NK produce fissile material in 2017? I'm talking about centrifuges and all that. Not the assembly of a warhead (however small) using the fissile material. Again, the article doesn't say that it's all done at Yongbyon. Do we have any sources? --RoyGoldsmith (talk) 10:59, 24 July 2017 (UTC)
 * I don't know about the production sites, but we have an article about warhead tests: List_of_nuclear_weapons_tests_of_North_Korea. The sources for that article may help you find more. --Lgriot (talk) 15:04, 24 July 2017 (UTC)
 * Idle googling suggests http://www.aljazeera.com/news/2017/05/north-korea-testing-nuclear-weapons-170504072226461.html as a good place to start, but first of all you have to skip the many existing wiki articles on NK nukes. Greglocock (talk) 20:07, 24 July 2017 (UTC)