Vacuum Chamber Construction

For posts specifically relating to fusor design, construction, and operation.
User avatar
Nicolas Krause
Posts: 230
Joined: Fri Sep 30, 2016 7:36 pm
Real name: Nicolas Krause
Location: Canada
Contact:

Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Thanks for the suggestion! I might try that if I get really desperate, but after a quote from a local tool and die maker of $263 to remove the two bolts, I've ordered some flush bolt cutters and purchased a cobalt drill bit and and am going to try and solve the problem myself.
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Vacuum Chamber Construction

Post by Richard Hull »

As I noted drill 'em out you may save the fine threads if very careful and have the thinned remnant threaded sections separate using a pick. If not, just slightly over drill and tap to the next size bolt. (consulting the bolt and tap tables for drill size and tap, of course). I do not know your clearance below for a nut, but as I originally suggested you can just clear-hole bore for a suitable pass through bolt and nut. So many ways to skin this cat and no big deal at all, of course.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Rich Feldman
Posts: 1470
Joined: Mon Dec 21, 2009 6:59 pm
Real name: Rich Feldman
Location: Santa Clara County, CA, USA

Re: Vacuum Chamber Construction

Post by Rich Feldman »

Thanks for sharing the quote. More money than I had guessed. For that, can we expect absolutely no new damage to the threads, and no new scratches, scuffs, or dings on the flange faces? Does the work include fixing of presently damaged threads?

Bolt cutters will leave the stub distorted more than cut-off with a hacksaw, angle grinder, or any kind of abrasive cut-off wheel.
At our local self-storage facility, the office staff has lots of practice cutting padlocks. Primary tools are long-handled bolt cutters and battery-powered cutoff wheel.

Can your milling machine help to hold the workpiece and start the drill at right spot and angle?
Other drill-jig ideas that come to mind:

1. A thick nut, screwed onto a couple of threads deliberately left on broken bolt. We know those are not co-axial with threads in flange. :-)

2. Spare Conflat flange with matching circle of through holes, and a short tubular bushing with right OD and ID.
Drill jig bushings are available in many sizes, for example 5/8 outside and drill R inside. https://www.mcmaster.com/drill-jig-bushings/

3. Any scrap of flat steel, say 1/4 to 1/2 inch thick, with guide hole (and optional counterbore) made on drill press. If made on milling machine, it could have properly placed holes for a couple of other holes in bolt circle.
All models are wrong; some models are useful. -- George Box
User avatar
Nicolas Krause
Posts: 230
Joined: Fri Sep 30, 2016 7:36 pm
Real name: Nicolas Krause
Location: Canada
Contact:

Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Hi everyone,

I've managed to drill out the bolts to a standard that I hope will allow me to seal the chamber. The process was a bit finicky but it went as follows, flatten the top of the bolt with a mill, drill a starter hole with a carbide spot drill, then drill through with successively larger cobalt drills. One hole went quite well, and the other not so well, part of the bolt is still stuck in the hole and almost appears welded. I'd continue to attempt to drill it out, but the 250$ drill press I bought off of Amazon is really not very rigid. I'll hold off on trying to improve things until I have access to a better workholding setup.
IMG_1080[1].JPG
IMG_1081[1].JPG
IMG_1084[1].JPG
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Vacuum Chamber Construction

Post by Dennis P Brown »

If you have a small circular file, carefully remove the remaining bolt threads till their almost flush (the abrasive force might also help loosen the remaining threads); then lots of tap oil and re-tap the thread carefully (use a tapered end tap only!) I've cleared remaining threads that way. Just don't over force it. Running a well oiled tap through a 'rough' threaded hole is always a good idea to be certain threads are clear and uniform again. Remember, very small partial turns (1/16) and back off and repeat as needed.

Anti-seize compound (never oil) is one's friend with steel on steel bolts into threaded holes.
User avatar
Bob Reite
Posts: 576
Joined: Sun Aug 25, 2013 9:03 pm
Real name: Bob Reite
Location: Wilkes Barre/Scranton area

Re: Vacuum Chamber Construction

Post by Bob Reite »

Looking at the pix, if it were me, I'd just drill them out to clearance size and put a through bolt and nut on the back, there is more than enough clearance for a nut it looks like from the photos.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Vacuum Chamber Construction

Post by Richard Hull »

Thanks Bob for recommending my original quick and dirty solution. Works every time. He has plenty of clearance there for that solution.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Rich Feldman
Posts: 1470
Joined: Mon Dec 21, 2009 6:59 pm
Real name: Rich Feldman
Location: Santa Clara County, CA, USA

Re: Vacuum Chamber Construction

Post by Rich Feldman »

Whether Nicolas ends up with threads or a through hole, it helps if it's in the right place.
This is where a drill jig, clamped to the work, is better than depending on rigidity of drills and spindles. Especially when first round drilling-out has gone so far astray. (+1 on Dennis's suggestion to first attack with a round file).

A spare Conflat flange or blank with through holes, bolted to the work, would be easy. It's all you need if drilling to that size. To use it for guiding a smaller drill, a bushing can be contrived from short metal tube and/or thin sheet metal wrapped around the drill. Thicker sheet metal formed into a tube with aid of a mandrel and hammer and anvil. Maybe even straight wires/rods in bundle parallel to drill axis, or wire wound around drill. See what's already on hand that would be not too tight, and not more than 0.010 or 0.020 too loose.
All models are wrong; some models are useful. -- George Box
User avatar
Nicolas Krause
Posts: 230
Joined: Fri Sep 30, 2016 7:36 pm
Real name: Nicolas Krause
Location: Canada
Contact:

Re: Vacuum Chamber Construction

Post by Nicolas Krause »

I appreciate all the suggestions posted here, I've ordered some small files off amazon and am going to try and remove the remainder of the bolt using them. In the meantime I've hacked together a bit of a crude mounting system using a hacksaw and some aluminum bar stock. I plan on cleaning up the cuts when I have access to better equipment. But for now it works.
IMG_1086[1].JPG
User avatar
Nicolas Krause
Posts: 230
Joined: Fri Sep 30, 2016 7:36 pm
Real name: Nicolas Krause
Location: Canada
Contact:

Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Just a quick update, but the files along with a small pick and a rubber mallet worked very well, and the last remaining bit of bolt has been removed.
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Vacuum Chamber Construction

Post by Dennis P Brown »

Very pleased to hear it all worked out - both literally and figuratively.
User avatar
Nicolas Krause
Posts: 230
Joined: Fri Sep 30, 2016 7:36 pm
Real name: Nicolas Krause
Location: Canada
Contact:

Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Just a quick update. I've got the chamber all assembled, and sitting on its frame. While I'm sure in the future I'll like having so many ports, at the moment it's mostly a lot of tedium anytime I try and put it all together. This is the second time putting it together today as earlier I was nearly done, but ran into some problems again with bolts biting into threads on the top port. Rather than fuss about with it, I disassembled the top half and drilled out the threads on every hole up top. Don't have to worry about that problem again! Tomorrow I plan on tightening up all the bolts, and pressurizing the chamber with a bike pump I have handy. I'll use a soap and water solution on the joints to check for any major leaks.
IMG_1104[1].JPG
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Vacuum Chamber Construction

Post by Dennis P Brown »

Your system looks absolutely professional and you've obviously become an expert machinist, as well. I'd find it hard to believe that you'll see any leakage using pressure/soap because that system is too well made to exhibit any significant leaks. Look forward to your further posts.
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Vacuum Chamber Construction

Post by Richard Hull »

I'm glad you took my advice on just drilling out those threads to make it thru-hole. Threads are great and even demanded in tight or ill-designed conflat mountings, but plain holes with clearance warrants that a bolt that is snapped off in no problem. A messed up nut just be cut off without having the hassles you have had with stripped or damaged threaded flange holes. In addition, thru-holed flanges are cheaper.

My motto is design with clearances so you can use common hardware bolts, if you can, and use thru-hole flanges.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Rich Feldman
Posts: 1470
Joined: Mon Dec 21, 2009 6:59 pm
Real name: Rich Feldman
Location: Santa Clara County, CA, USA

Re: Vacuum Chamber Construction

Post by Rich Feldman »

Anybody here using nut plates instead of single nuts, to use fewer wrenches and lockwashers?
CF-Flange-Plate-Nuts.png
CF-Flange-Plate-Nuts.png (75.69 KiB) Viewed 10044 times
https://apexvacuum.com/product/conflat- ... late-nuts/
All models are wrong; some models are useful. -- George Box
Frank Sanns
Site Admin
Posts: 2119
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

Re: Vacuum Chamber Construction

Post by Frank Sanns »

I use those on my 2.75" flanges. They work great especially since I have so many connections of that size.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Vacuum Chamber Construction

Post by Richard Hull »

I use them on all my 2.75 conflats just like Frank. They are a real time saver, but at $6 or more per set of 3, I have never bought any as regular nuts are just fine. All that I have came off a number of surplus system disassembly efforts in the past. I guess I have about 4 full sets on hand. I used them on the abortive fusor V alpha. Now dismantled, I have them all at my disposal once again. I have 100's of nuts on hand. These plate nuts are handy for through hole flanges where a wrench to be placed on a nut for tightening is almost impossible to get to. They do serve a glorious purpose at times. To conserve the few I have, I have been known to use one in tight spaces and 4 regular bolts and nuts on the easier to reach parts of a flange. There are no vacuum police to regulate how they are used.

As far as I think, based on what I have and need in future, I'll probably never have to actually purchase any plate nuts.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Nicolas Krause
Posts: 230
Joined: Fri Sep 30, 2016 7:36 pm
Real name: Nicolas Krause
Location: Canada
Contact:

Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Dennis I appreciate the kind words, but reality is a harsh mistress. Looks like I'm going to be redoing some of the welds!
IMG_1106[1].JPG
User avatar
Nicolas Krause
Posts: 230
Joined: Fri Sep 30, 2016 7:36 pm
Real name: Nicolas Krause
Location: Canada
Contact:

Re: Vacuum Chamber Construction

Post by Nicolas Krause »

I was concerned about missing leaks on the underside of the chamber since a lot of the soap solution had dripped off, so I just completed a second leak test in the bathtub. Virtually all of the leaks appear to be coming from one of the main rings on the hemisphere. I'm unable to see any other bubbles from the underside to that's nice, there were also a couple of small leaks from some conflat seals I evidently hadn't tightened enough.
IMG_1107[1].JPG
User avatar
Rich Feldman
Posts: 1470
Joined: Mon Dec 21, 2009 6:59 pm
Real name: Rich Feldman
Location: Santa Clara County, CA, USA

Re: Vacuum Chamber Construction

Post by Rich Feldman »

Good clean toes. :-)
Assuming the main ring welds aren't leaking ...
Is it possible that a thick steel ring was rendered non-flat, beyond tolerance, by the welding operations?
I guess that could be checked by assembling without Cu gasket, all bolts finger tight, and check the joint all the way around with thin feeler gauge.

Would an elastomeric seal tolerate more non-flatness than traditional copper ring?
All models are wrong; some models are useful. -- George Box
User avatar
Nicolas Krause
Posts: 230
Joined: Fri Sep 30, 2016 7:36 pm
Real name: Nicolas Krause
Location: Canada
Contact:

Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Hi Rich, the bubbles are very clearly coming from the connection of the hemisphere to the ring, and the hemisphere's don't rock against one another when I press them together, so I think the most likely culprit at the moment is the weld itself.
User avatar
Nicolas Krause
Posts: 230
Joined: Fri Sep 30, 2016 7:36 pm
Real name: Nicolas Krause
Location: Canada
Contact:

Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Very happy to report that after a quick welding session, the welds appear to be sound. Visual inspection identified a couple of small holes, and just to be on the safe side I welded a few more spots that looked suspect. I repeated the soap and water test with the bicycle pump and no bubbles appeared! Next steps are to complete the program and pcb for my vacuum thermocouple gauge. I'll then be able to hook up my backing pump.
IMG_1118[1].JPG
John Futter
Posts: 1848
Joined: Wed Apr 21, 2004 10:29 pm
Real name: John Futter
Contact:

Re: Vacuum Chamber Construction

Post by John Futter »

Nicolas
Excellent keep at it
User avatar
Nicolas Krause
Posts: 230
Joined: Fri Sep 30, 2016 7:36 pm
Real name: Nicolas Krause
Location: Canada
Contact:

Re: Vacuum Chamber Construction

Post by Nicolas Krause »

Progress has been slower than I'd liked this summer. I'm still waiting on some parts to complete my thermocouple gauge sensor. The pandemic has slowed mail delivery considerably. In the meantime I've added some bits to the chamber and its starting to look operational. The mechanical backing pump works just fine but until I complete the vacuum gauge there's not much sense in pumping the chamber down. The vacuum line consists of two valves, a ball valve at the mechanical pump and a butterfly valve at the turbopump. In addition I have most of the components for the high voltage feedthrough either delivered or on order.
IMG_1132[1].JPG
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Vacuum Chamber Construction

Post by Richard Hull »

It is looking super professional and you have what it takes! You have shown it through your numerous reports as those baby steps were taken. This is something you will long remember and be proud of, not so much of the finished product, but of the struggle and effort. You have proved something to yourself about yourself.....That will last.

Oh, I am green with envy over that beautiful blue anodized lab build frame. WOW! In case you haven't noticed, I like blue around my fusor. I dare not think of what that frame and all the bits and pieces set you back.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Post Reply

Return to “Fusor Construction & Operation (& FAQs)”