{another ribald wisecrack about KNOBS goes here}

 The cleaned, polished, and re-inked... article.
Much verbiage about one simple task.

What's another word for 'knob'?

 I regret that I apparently did not snap a 'before' picture of this knob before restoring it.  It was actually quite a lot of work, tho I don't think the time or effort shows. It's not perfect, but I didn't think it needed to be a show piece. It's a control; it'll just get dirty again.

 This was just something to do that let me feel like I was making progress, while I am slightly stumped (for lack of a pilot lamp!) on the table feed.  I don't want to really dig into the feed  until I have got the motor drive licked.

 So anyway: before, the speed knob was scratched, dull, and covered in a hard film which no doubt combined thirty years of machining fluids, various dusts, and skin cruft (oils, perspiration, cells).

 The first thing I tried to do was match it to a nice knob from The Knob Collection*, but alas, no such luck.

 So I decided to restore the knob.  First, I scrubbed it with a toothbrush and some Greased Lightning.  That got it clean after multiple tries.  I think I also had a session with IPA in there.  I'd have used acetone too, but I am out at the moment.

 The top surface was easy to polish on the buffer, but the side flutes were less fun.  I managed a fair job with a small buff wheel intended for a dremel, chucked in the drill press. This I charged with soft green compound intended for hard plastics and soft metals.  Same stuff I used for the top with the bench buffer.

 The line where the flutes meet the skirt of the knob were a pure S.O.B. to get the polishing compound out of.  Managed that with paper towels, cotton swabs, and elbow grease, eventually.

 The white markings looked awful.  I dug out the circle and the line's groove with a dental pick, then cleaned them with a bristle brush and IPA.  I would have preferred acetone for this.

 After that, I carefully introduced some white nail polish to the dot... but when I attempted to ink the line, I got it everywhere.  New plan: fill in the line properly, let it be a bit messy, then wet-sand the excess off, and repolish the top since that part is easy.  This we then do.

 I thought I was done, but now I've seen this photo, it looks like there is a little more to take off, because the line isn't really that wide.  One more brief session ought to do it.  The thin line looks better, very sharp.  Maybe I should not have posted this until I got a truly final photo, but does anyone really care that much about my knob?

_____________
 * It's about one 2lb coffee can full, but with all of them in bags; I won it from the door raffle at a radio collector's meeting I only went to once.

 ~≈{👁}≈~

looking into their (gear) box, polishing my (speed control) knob

 

 Uh-oh, and yet, completely expected. The Experts On The Internet™ suggested I would find the lower housing (with limit switches and the user controls) full of oil from the gearbox above it, because good O-ring materials weren't widely available yet in the 1970s so they eventually softened and swelled out of place, or hardened and cracked.  Silicones and fluoropolymers (ie; Viton™) solved so many people's problems.

 I couldn't see any oil in the sight glass so I gambled and opened the gearbox.  Minor mistake, it still had some oil in it. It has less oil in it now. (it's all old and horrid looking and was always going to be replaced anyhow)

 I cleaned up the mess on the drive housing, and put a pile of Oil-Dri™ on the pile of oil on the floor.
It will take a few days to get most of the oil up.

 It needs a new sight glass, and I was surprised at the cost of simple pressed-in (at least I think it is) sight glasses, so I'm considering making my own.  A fun little project IMO except I can't start it until after I have moved the lathe. {fresh round of sighs}

 I need to take a hard look at what's inside the gearbox / switchbox assembly.  From what I saw at first, it looked like the mechanism could be greased and forgotten about - ie; no oil.  A lot depends on speeds of meshed gears which I can't look at yet because nothing works right now.  It sure would be nice to not have to worry about figuring out new seals if I return it to the factory condition.  Why are the limit switches inside the gearbox assembly and why is the limit function mechanical?  Why is any of this thing, the way it is? WHO IS RESPONSIBLE FOR THIS MERDE-MONTRER? (ahem)

 The design of this table feed is... eccentric... at best.  They farmed out the motor drives, but I don't think they farmed out the table feed / motor assembly.  They really should have.

 My summer nanny for a few years was fond of saying, "if you can't say something nice, don't say anything at all."

 Okay: Bridgeport made great milling machines. ;)

I've just made a $500 knob, haven't I?

 Right then: the table feed control panel has a knob (phenolic!) which, due to the depredations of being mounted at the end of a milling table, and thus subject to a certain amount of Strange Liquid Rain, and Metal Dust Hail &etc.  It is also handled by dirty, sweaty, human hands.

 It was not in good shape.  Restoring it was clearly a project so I first looked in my Can O' Knobs and found no matches, so then I decided to hand-restore the damned thing anyway.   This required getting creative with polish buffs running in the drill press, and some careful work on the bench buffer.

 I am now drying the white nail enamel I put into the dot and groove.  The groove was simply impossible to fill without being messy so I accepted that I'll have to wet-sand the top of the knob and re-polish it.  This is not onerous; polishing those damned flutes on the side, was.

 And that's the story of how I polished my knob and then clamped it in a vise.

 ~≈{👁}≈~

CRASH

 Apparently, when I was working out where and how to mount my over-built DIY collet rack, I must have assumed I would never have it cranked up and all the way back?  Never assume.

when two ships pass in the night...
and they love each other very much...

 At some point in the past, I actually bent the base/mounting part of the collet rack by hitting it here, while cranking the table and being too focused on the work -- but the collets are springy half-hard temper and no apparent damage was done to either motor or collet.  Even so, um, stupid?

 At some point in the future, I gotta cut up the mount and re-jigger it with some diagonal bits, moving the rack 4in higher but also I need to remove the base plate that mounts to the mill and pound it flat again before re-welding everything, because last time I let a couple welds shrink and it bent that plate out of flat and made the whole thing slightly wobbly.

 I seem to spend all my time fixing my tools instead of using them.

 And it's time to admit that I am straight-up miserable at welding.  Part is lack of tooling, part is lack of training / watching YT videos. <_<  But manage warping I cannot.

 And in the basement, a complete little 3D printing lab with all the toys, still languishes all alone, waiting for me to play with it.
 
 I heard once that you can make stuff with a shop. Some day I'd like to try that. 👽

 ~≈{👁}≈~

My God! My machine is sagging under its own weight!

(and so is yours)

 I happened to put a precision level on the mill table because I needed a level surface to check a different, cheaper level, I didn't want to unstack the crap on top of the surface plate (cover) which I am totally not using as a work surface at all, and I thought I had leveled the mill; Ghu knows, I pounded enough wedges under it to do so.

 But the level showed off by two graduations; um, I don't remember what the graduations mean, frankly.  Much less then a degree of angle, I remember that much.  There's a card in the tool chest that has the info, but I am thirty feet away inside the house, and with my hip/leg pain of late, I dislike changing positions.  On the same surface, the bubble in the cheap level I wanted to check just disappeared.  The precision machinist level from Starrett is more sensitive by a couple orders of magnitude, than the no-name woodworker's level.  But I digress.

 I thought I'd leveled the mill table, so I moved the level to the middle of the table.  There, it was level.  Moving the level to the other end, I find the table is out of level in the other direction.  Could that massive hunk of cast iron be bent and/or bending under its own weight?!?  NO WAI. 😱

 I moved the table to one end and measured the center again, and it's close to level but not as perfect as when the table was centered.  The far end was worse.  Same-same when I move the table to the other end. 

At this point, a picture began to develop.

 Number Uno, the table really does sag under its own weight, and that's normal!  A bit of research reveals that they sag when they are new.  If Bridgeport made it 2X or 3X as thick, it would still sag, just 2X or 3X less.  To take the sag out down to a tenth or so, would require a nine inch wide table to also become nine inches thick.  At which point, it would weigh as much as the rest of the machine.

 Numerus Secundus
 More importantly, that sag doesn't matter, because that isn't where one is machining.  The saddle holds the table up to the right height as the table moves under the spindle.  The only part that really matters (all other things being correct) is that the table not tilt on the saddle.

 The friend I bought the mill from told me something about how the saddle under the table is the actual flat reference you are milling with, ie; the saddle ways - it's not the table.  I don't remember what we were talking about, but I now perceive I did not think through all of the implications that I originally got from his advice.  Sometimes I learn quick.  Sometimes I learn slow.

 It also appears that my table does tilt - slightly - when extended, which I believe is a loose gib problem.  And that does need fixing because the whole table is tilting, work and all, under the cutter.  That's bad if it is significant, but fortunately that's a big if.  I think the saddle gib can be adjusted without taking anything apart.  I'll look during my second smoke trip of the morning.  It is possible my gib is worn unevenly and if tightened, will bind, making it harder to move the table (rough on the power table feed I am fixing) if I try to tighten it.  It is possible it was loose for whatever reason and just needs a snug.

 It is possible I will do the math off the level's reading and think to myself, "I can live with that".  Time will tell. 

 Okay, I did the math.  The calculated sag (making a few assumptions along the way) is over .009in.
That's a lot.  And there are multiple things contributing to that, not just the bending of the table.

And yet it doesn't matter.

 But man!  This just goes to show there is more than one way to measure something.  If I had actually set out to measure the sag of my table this morning, I would have wondered what and how I would mount my tenths indicator on.  I still can't think of a way.  Maybe building a heavy stand that sits on the floor?

 My reference point ought to be the spindle nose.  How could I attach something there (like an enormous Indicol?) and then hang it two feet out to pick up the end of the table?  I'd have to build a gantry/truss structure so it wouldn't weigh much, it has to be rigid in two dimensions, and uh, yeah, I'm not making that unless I'm gonna use it more than once. 

 But drop a level on the table and with a bit of math, I get the answer without having to make a one-time, single-purpose fixture I'll never use again.  The reader is referred to the Shop Math section of your copy of Machinery's Handbook. ;)

"When will I ever need any of this weird math?
I'm not going to become an engineer, I want to work
with my hands, maybe be a machinist or an electrician!"

 ~≈{👁}≈~

pushbuttons, toggles, and damfoolishness

"Inside every project are a bunch of smaller projects, trying to get out." - anon

 Damfoolishness first.  I had a careless/clumsy moment, the drive box hit the floor, and the power switch broke its fall:

 The toggle switch is a strange one from Tektronix, because I now perceive the baton was hollow plastic, not metal.  Sheesh.  Fortunately, the switch type is nothing special, and they are cheap.

 Next, the buttons.  I've been thinking about safety a lot lately, started making small tweaks around the shop.  Everything short of putting guards on my machines, heh-heh.

 One of the things that came to mind is this: suppose your spouse or neighbor hears you hollering for help (because your lathe has grabbed your hand, and wrapped your arm around the work, breaking it in seventeen places). They rush in and want to help.  How do they turn off the machine?  Maybe they've never seen a machine tool in their life, or maybe its your spouse but they just never made a study of the thing.

 You know what all those buttons, knobs and levers do - they don't - but you're busy.  There's eighteen of them on the average mill.  And you're probably hollering (I'm being optimistic) so your rescuer is panicky.

 OSHA and other agencies worldwide solved the access-to-dangerous-spaces (where the whirling bits are) the best they could with movable shields, light curtains, NO FOOT PEDALS, dual hand buttons and so on.  But just in case, every machine has an Emergency Power Off which is larger than all the others, it is orange or bright red, and typically on a yellow background close to "eye level" for an average person.

 I bet your machine doesn't have shields or light curtains.  Mine sure don't.  ^_^

 Well, my lathe had a red mushroom-head stop button when I bought it, but it could use better labeling. It's a bit of a reach too because they put all the buttons at the back of the headstock instead of the front somewhere. That appears to require a major re-structuring of the headstock, so it's a toss-up whether it will happen in my remaining forty (I'm being optimistic) years. <_<

 I originally installed a turn-to-select knob to control power to the rotary phase converter (which feeds power to the mill motor, if it's turned on) specifically this one:

 I wanted to change it to a modern EPO type mushroom head.  These were my options from what I had in my parts drawers:

 The big one on the left is a drop-in for the existing switch, but it is so big, it would cover up the "PUSH OFF" text on the tiny little Hoffman box the switch is mounted in.

aside: those old Telemecanique panel components are
super easy to install, change parts on, change functions...

 The next one to the right was no good because it's a momentary button, which is no good - only useful in telling a relay to drop out, but that's not what we want.  We want positive actuation of the actual switch contacts.

 The next one is exactly what we want; when it is pushed in, it positively holds the contacts open, and it stays firmly in either position.  Pull to run, and it too is a drop-in replacement.

 But the complete replacement from Itek on the far right has one thing going for it, which I like: you don't turn the power back on by pulling, you reset it by turning.  Howsomeever, I would need to buy new contacts for it, I would need to embiggen the hole slightly, and right now, the Telemecanique block is the ground for the whole box, very convenient, its jack screws dig through paint into the metal, no extra holes.  So the Itek doesn't seem worth the trouble.

 In the end, I went with #3.  To change it, the switch/lamp panel mounting body has to be loosened but not removed - two straight bladed jack screws on the inside of the panel.  Then the switch/lamp/whathaveyou bayonets out, the new actuator/lamp/whatever bayonets back in, re-tighten those two jack screws and you are done.  Voila:

I wish it had better labeling; at least my block printing is legible.

 I had to change the contacts too (from NO to NC) but I had spares.  It's one mounting screw per pole, and BTW they have good, easy to access wire clamps.  AFAIK, none of their kit is made the same way any more, more's the pity.*

 By the way, the reason this switch is in such a rugged, sealed, flanged box is that the available fault current from this circuit is several hundred amps before the breaker (motor time delay type) trips, which translates to a released power of 43,200 watts minimum.  That's a lotta calories while that breaker decides whether this new load is a big motor or a short cirtcuit.  If something shorts in that box, the flanges direct any arc flash or other ejecta away from the operator.  That's the downside to not having some relays in a box somewhere far from the operator.  OTOH, this is more failsafe. The box is also gasketed, don't recall what NEMA equivalent, but it'll keep out splashes of cutting fluids.

 Those familiar with industrial controls know that panel switches are only good for "pilot duty" which in most cases, including these Tele contacts, means 240VAC @ 10A.  The phase convertor pulls about 3A when idling, 5A when the motor is running.  Load or no load is nearly the same.  The actual increase in electrical load when machining is very low on this machine, the way I run cutters with low CPT loads.

 That said, those contacts could, in theory, over a long time, weld together.  I think I will install a pair of these QuenchArc components I just happen to have lying around (bought for air compressor), across those two contacts, eliminating arcing and extending their life past the life of the mill, in all likelihood. As soon as I remember where I stashed them. >_<

It's not paranoid to try to do a good job while keeping a weather eye on potential misfortunes.

______
* I believe this entire line of products was rendered obsolete by a Euro-initiated safety standard which disallows any conductive parts passing through the panel, which describes most of the old series Telemecanique devices.  D'oh!

 ~≈{👁}≈~

such power cord! many thought! wow! very trivia!

 This is about the power cord for the mill's power table feed.  This power cord goes between the motor drive housing on the side of the column to the power outlet.

 The original cord, dating from the mid-70s, was in astonishingly good condition.  After being exposed to cutting fluids etc for decades, it shows not the slightest amount of cracking or crazing.  The jacket is still quite flexible, the conductors inside are as well.  I could have re-used it...

 But it has paint and oily grime on it, and I am out of acetone, so I can't remove those things.  And with all the effort I've made to clean up all the parts, I can't have an ugly power cord hanging off it.

 It has a regular plug, and because the cord hangs down from a height, I prefer to make the plug a right angle type.  So I would be cutting off the original plug anyway.  I wanted one gauge larger of wire (from 16 to 14) anyway, and I wanted a little more flexibility, so I decided to replace the factory cord with SOW, which I have plenty of, on-hand.  It's black tho, and the original cord matched the machine's paint.  Sad face.

 But the SOW is larger in diameter than the factory cord and will not fit the original 3/8-ish cable gland on the housing.  Fine, okay, I found a cable gland of the right size (my last one) in my parts piles.

 Cleaned up one old one, installed one new one, got cables into glands, realized they now need to be swapped to fit the new arrangement of guts.  Thankfully I realized this before I started soldering.

 So, remove cables, remove glands, swap glands, re-insert cables. You have to put the glands into the box in a specific order, and tighten the first one before installing the second, otherwise, you can't get both of them tight...

 I'm actually still waiting for the pilot light (a maybe, I may not like the part when it arrives) so when that is finally selected and installed, I can do a proper and final fit test, to make sure it doesn't hit any of the parts on the mounting panel.

 It occurred to me that collector mindsets being what they are, some future owner may want the original power cord, so I'm keeping it around, and I'll clean it up when I have more acetone.

Now I am waiting for the rt. angle plug to arrive (and many other things besides).

EDIT, later: rt. angle power plug had been installed.  Turned out I ordered the wrong diameter pilot lights, so that item is still open.

 ~≈{👁}≈~

What are fiducial marks and does my banker need to know about them?

What's wrong with this picture?

It's subtle; There are two dots, they're supposed to be red.

 When I first took apart the power table feed for my mill, and removed all the guts from the mounting panel, I noticed whoever had made it hadn't cared to make the mounting panel's drilled holes symmetrical and mirror-image.  It went in only one way.

 To save myself time flipping and spinning the panel later to find the right orientation, I put "fiducial marks" on the housing and plate.

 And then one day when I was reassembling everything, and realized it was time for a fit check... oh.

Haha: everything fits!  Provided I spin the plate 180º because I forgot about the problem when I started rebuilding.  Oops.

 Well, the simple solution is to drill out the holes.  This bugs me because inevitably, one of the holes will show some hole under the screw head... where no one will ever see it... but I'm a bit anal-retentive, if you haven't noticed.

 On the very other hand, you can see where I already had to re-drill this plate for the motor drive heat sink.  (JB Weld, The Hole Eraser) Perhaps I oughta make a whole new mounting plate... I probably won't... but you never know...

 And then there's the preventably random engine turning on the plate... the plate no one will ever see again... but it bugs me. I was probably thinking "no one will ever see this again".

 The point is to do a better job of everything than the factory did in the 1970s.  I'm trying.

 All this stuff would go a lot faster if I didn't hurt all the time. And if I could still multi-task.

 ~≈{👁}≈~

Huot drill indexes, another unsolicited attaboy

  Many of my readers will share my desire to buy American-made tools whenever possible, unless it means sacrificing quality. Sadly, yes, there are a tiny few American companies that either make junk, or have a mixed bag of quality.

 But this post is not about them.

 Huot Manufacturing has been around for a hundred years.  Literally; they were founded in 1926.
They literally invented the drill index, and to this day, those are among their most popular products.  100% made in St. Paul, MN.  They aren't even outrageously expensive.

 I just paid around $60 for this index which has three sections for fractionals from 1/64 to 1/2 by 64ths, numbered drills from #60 to #0, and the lettered drills from A-Z.

 Herewith my on-arrival review. 
As usual, I bought this with my own
money, Huot doesn't know I exist, I am
not for sale, my opinions are 100% my own. 

The only other times I review something is if
something on it breaks sooner than I expected,
or I realize I've owned something for twenty years
and it has quietly done its job without breaking or
getting in my way, and that too deserves a mention.

granted, I only have two or three letter drills, so far...

  This replaces two indexes I had for fractionals (a Craftsman) and numbered (Harbor Freight).  It also adds an index for letter drills, which previously just rolled around in the drawer.

some differences:

    • the HF index has the thinnest steel for the housing, by just a few thou vs the other two.  OTOH
      the racks inside are paper-thin, and it's paint is falling off; typical for the source (and the drills
      that came with it are as hard as a bad day - no temper at all - will snap from a stern look, LOL)

    • the Huot index has a housing the same thickness of steel as the Craftsman, and slightly thicker
      steel in the inserts / drill holder parts

    • the Huot index has a nice paint job, halfway between spatter and hammer tone.  For a minute,
      I wondered why it seemed a bit rough, until my senile old brain tumbled: it is non-slip even
      with greasy / oily hands, without being grabby or lint-collecting

    • the Huot arrived with two racks (out of eight, I think?) which had a bit of sharp punched / wire
      - edge which was sharp enough to cut, but both were easily deburred in less than two minutes
      with a small hand stone

    • despite it holding every standard drill used in America (metric indexes are a complete but seperate
      product line, and one I don't think I need) the Huot index still fits in the same tool chest drawer
      the other indexes did, with a bit of re-arranging, and it's real nice to be able to open that drawer,
      open one lid, and have all my drill bits easily accessed.

    • The old indexes A) did not open in a convenient direction and B) the tabs and wires meant to
      pull all the racks upright when you opened the lid (a feature!) never worked right, and got in the
      way more than they helped, so I cut the wire bail and filed off the tabs.  The Huot hasn't got that
      convenience feature (how would you even implement it?) and frankly, I consider that a fine
      thing and not missed.

    • Oh, I almost forgot a major feature of construction:

 Old 'n' Busted (old Craftsman index) is on the left.  Both it and its Harbor Freight cousin sport a "hinge" consisting of just two folded sheet metal tabs.  In all fairness, they actually did hold up okay for decades.  That doesn't mean it's not cheap construction.

 On the right, The New Hotness, the hinge on the Huot index. Not only does it sport a piano hinge, the hinge wire is staked every few tabs.  We've all had piano hinge objects from which the wire kept trying to migrate out one end.  This one will never, ever do that.  I was impressed with construction and finish.

 That's everything I liked and didn't like, without having used it, any at all, yet.  Right now, even allowing for my very few gripes above, my recommendation (if you're in the market) is to BUY HUOT.  If I discover any warts while using it, I'll post about them later, as usual.

EDIT, a little later: I sure like this drill index.  It just feels less cheap, less loose, than the two indexes it replaced.  I haven't needed letter size drills often over the years, but they can be had cheaply enough as NOS on eBay, so I will pick up perhaps one per month and eventually fill that section in.  Those I would most likely use to make tapped holes for small plumbing fittings or similar.

 ~≈{👁}≈~

Ohhh, so that's why we bake the enamel one layer at a time!

That paint was harder than a bad day.

 I just now finished this.  It took me a lot longer than it should have.  The painting was routine.  Getting the paint off the lettering was not.  It turns out that baking enamel on as I do has the desired results - that stuff gets tough. It will not crack or chip, and it resists abrasion.

 I started with wet-sanding, but this went very slowly, even with nice, fresh/sharp, silicon carbide paper in a semi-course (200) grit.  Harrumph.

 Next I tried mounting it on the mill and running a little (sized for a Dremel) convolute abrasive point over it.  That seemed to move the paint around a bit.

 Finally, I decided to get aggressive; I put my largest fly cutter in there.  That did the trick.  Even so, it required multiple passes, and I had to touch up the 'ON', 'OFF', and the ®egistered Trademark symbol by hand-sanding with one of my paint-stirrer sanding sticks.

 The enamel finish was dulled in a couple of places by my carelessness during the first attempts to do it, and I haven't decided what to do about that.  First impulse is to mask off the shiny bits and just spray, but I worry the mask boundaries will look like dog yack.  Actually I think I will try wiping the dull spots lightly with acetone first.  We'll see.

Er, well, it turns out I own a buffer, with a selection of wheels and compounds.  I forgot. >_<  I'll mask off the lettering with aluminum tape and have a go with that, first.  We'll see, we'll see...

 The next step is wiring up the motor drive panel and its relays with the cable from the drive proper.  I'll need to cut back a bunch of the cable for service loop, and it's very tempting to insert a connector between electronic mounting panel and the housing with cables.  I like serviceability, even though I am  building this so it won't likely need serviceing again until the day it is scrapped for its iron. :(
(my ghost will haunt the person who does this, until I've driven them mad)

 I probably won't start that today because I have pain-brain.  I would probably cut the red wire instead of the blue wire and blow up the speeding bus. 😂 I need to think about the connector when I can think straight.  Oh shoot, I don't think I own a pair of crimper handles any more (the ones that accept different dies).  I'll have to look.  I think my regular ones (I had two) were in the tool kit that got stolen out of a rental property thirty years ago and I never replaced them because they are expensive.  Grump.

 I guess I'm competent enough to install the power cord, umbilical, and fuse holder into the box.  I might replace the plastic power cord with some nice SO cable. I have to give the original cable a hard look.  It doesn't move, so it's not as if it needs to be more flexible than the basic PVC, and the original power cord doesn't actually seem to have any age defects.  Perhaps I will let sleeping dogs lie.

 ~≈{👁}≈~

Does UV-C light speed polymerization of Boiled Linseed Oil? maybe a little)

 One camp says UV (such as in sunlight or from mercury vapor lamps - the shortwave stuff, not blacklights - hastens the curing of BLO, the other camp says no, only oxygen matters, and not even heat will speed up the process because it is not drying in the usual sense. Evidence - and I'm here to tell you that most woodworkers are not good scientists - suggests it's a little of each column.

 We are Fooling Around with every intention of Finding Out:

100 watts (electrical) of short-wave UV

 I actually put cardboard around it because I wanted to work near it, and use the bench, and even the stray scattered light from these things will give you - and your corneas - a sunburn, with bonus increased risk of skin cancer thirty years later.  Stay away from the evil-looking death light. :D

The strongest peaks in the mercury vapor spectra are:

Wavelength (nm)  Name  Color 184.45 ultraviolet (UVC) - !! 253.7 ultraviolet (UVC) - !! 365.0 I-line ultraviolet (UVA) 404.7 H-line violet 435.8 G-line blue 546.1 green 578 yellow
The brightest peaks are the UV, blue, and green lines, which is why it looks like an eery sort of blue-green color to our eyes.  The yellow line is weak, and I suspect we can all be grateful for that.  They used these in street lights (for you youngsters) before LEDs and before those, High Pressure Sodium.
UV light speeds polymerization of some resins, and with the UV-cure resins used in 3D printing for example, it can just be UV-A (blacklight, harmless).  But in theory, higher-energy photons should do a better job of polymerizing, right?  Well, we get higher-energy photons by going to a shorter wavelength.  Kids don't try this at home; shorter wavelengths (UV-B & UV-C) will not only sunburn your skin, they will sunburn your corneas.  (feels like sand in your eyes for weeks, and can cause permanent damage to your eyeballs.  You need goggles or UV-coated eyeglasses at the very least.  Thick glass lenses alone will stop UV-C, but for UV-B you need an anti-UV coating.  EDIT: early indications are that UV light may speed polymerization somewhat, it is not a dramatic effect, and not worth obtaining shortwave UV sources for this purpose; just use the sun, which also provides heat and fresh air which seem to be the primary oxidizers.  UV-C falling on some surfaces especially metal screens will create ozone, and it's possible that is the cause of UV having an effect for some and not others (people reporting online).  I did not notice any more ozone than usual - the lamp head is metal and the unit does make a small amount of ozone by itself.  And this limited effect was using a very nasty, hazardous, UV-C source which most people won't have access to anyhow.  If it's speeding up the polymerization only a little, there is no sense spending $400 on a 100w mercury vapor lamp and ballast.
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