Vacuum Chamber Construction

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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause » Fri Jun 29, 2018 12:44 am

After a bit of a school enforced break, I've finally managed to find some time over the summer holidays to return to the machining of my vacuum chamber. Using a carbide spot drill, a pilot hole was drilled and then subsequently enlarged to 3/8 size with a number of drill bits. I now plan on using a step drill to enlarge the whole to close to its final size and finally a boring head to take the hole to the precise diameter. The second hole visible in the photos below is from an earlier machining attempt that didn't work out.
image1.JPG
image2.JPG
I do however have a question about workholding. I'm using 4 toe clamps on a tilting table to hold my workpiece in place. The hemisphere seems to come loose rather regularly with the setup. After monkeying around with it for a bit I was able to find a seemingly stable solution that held the workpiece securely, but I wanted to know if there was a better way to go about holding the hemisphere. Or if I'm simply setting up the toe clamps in a way that doesn't use them effectively.
image3.JPG

John Futter
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Re: Vacuum Chamber Construction

Post by John Futter » Fri Jun 29, 2018 8:00 am

Toe clamps directly to mill slide bed
t bolt through the hole in the top with machined aluminium disc to fit hole now held top and bottom you will need to offset mill head to correct angle to bore hole.

enjoy

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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause » Mon Aug 06, 2018 11:12 pm

Thanks for your suggestion John, I've cobbled together a better workholding solution as a result. A t-bolt in the middle of the hemisphere is connected to a long bolt, which has a couple washers on the end. I plan on adding a dab of superglue between the washers to hold them together as a unit and make assembly and disassembly of the work piece a little bit less finicky.
image1.JPG

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Nicolas Krause
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Re: Vacuum Chamber Construction

Post by Nicolas Krause » Sat Oct 06, 2018 7:29 pm

Before returning to school I was able to complete the first angled port on one of my hemispheres. Now that I have the series of operations figured out I anticipate that I'll be able to complete the remaining ports much more quickly. I'll likely be able to get to it over winter break or failing that early spring once school breaks for the summer. A cheap step drill from china performed very well to rough out most of the hole and a boring bar was used to take it to final dimensions. Initially the boring bar was too long and excessive chatter resulted, but I switched to a much shorter tool and chatter was greatly reduced and surface finish improved drastically.
image1(1).JPG

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Richard Hull
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Re: Vacuum Chamber Construction

Post by Richard Hull » Mon Oct 08, 2018 5:10 am

Great work! You are using the exact same tilt table I use on my milling machine to do such work.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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