ec, as I understand it).
closest "ideas" (if you want to call them that) that I've come up with inv olve modifying aluminum extruded-type cabinets, but I haven't found one a) large enough, or b) semi-custom off the shelf.
earch business.
aucho) via my Alexa as I type this so please forgive the rambling. :) All help appreciated!!!!
aper
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use a thread forming tap,
There are thread-forming screws that don't generate as many chips as self-tappers. One of those would probably do at least a few boxes.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Curious design, that one. Has no reliefs cut into it!
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The screw holes aren't closed tapped holes, they are open on the sides, to the interior of the box.
The self-tapping screws dump shavings inside. If we tap the holes, to use regular screws, the taps tend to break.
The extrusions could have had solid cylinders for the screw holes, drilled and tapped, but I guess that would cost more.
Hammond also uses weird self-tapping screws, #6 threads with #4 size flat-top heads, so it's mainly useless to experiment with using different kinds of screw threads. It's ugly.
We should do our own extrusions one of these days. The Hammond boxes have other problems.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
it doesn't cut it forms the thread by displacing material
like rolled threads on screws,
Long [threaded] rods with couter sunk nuts between front and back? |==----------------------------==|
eehh
The screw holes aren't closed tapped holes, they are open on the sides, to the interior of the box.
The self-tapping screws dump shavings inside. If we tap the holes, to use regular screws, the taps tend to break.
The extrusions could have had solid cylinders for the screw holes, drilled and tapped, but I guess that would cost more.
Hammond also uses weird self-tapping screws, #6 threads with #4 size flat-top heads, so it's mainly useless to experiment with using different kinds of screw threads. It's ugly.
We should do our own extrusions one of these days. The Hammond boxes have other problems. ========================================================
With the side of the hole open there will be a bit of spring so I wonder if a thread forming (not cutting) screw for plastics would work and be cleaner? Look at part
-- Regards, Carl Ijames
They're selling you the wrong screws. You want screws that deform the metal rather than cutting threads. The ones we use are called "tri-lobe" screws.
I don't do "instruments" but you've seen (and use, apparently) castings for such. They aren't difficult to design, as you well know. Hell, just steal a design and size it for your use.
If you look at the drawing of a Hammond extruded box, you'll see that the screw hole is not circular, and has one side open. For example: The star like pattern has several functions and problems.
- It forms an addition PCB slot.
- It provides less surface area that must be deformed by the screw.
- If provides a place for the chips to collect after tapping. This can be a problem if you remove the screws and the chips fall into the electronics.
Notice that there are no dimensions on the screw holes. That's because holding tolerances on an extrusion is not easy. On some extrusions, the screws (usually 6-32) will fit nicely. Other time, they will either jam or fall out. I've seen both problems from the same manufacturer.
I once tried to solve the problem by using nylon "push in" fasteners and threaded screws but without threading the extrusion. It worked, but only if the fastener wasn't removed after installation. The nylon would be deformed and would not hold the 2nd time.
Common straight fluted taps don't work well on ductile metals that have seizing problems due to galling, such as aluminum. Try a spiral tap next time: or use some aluminum tapping lube: Use a drill press with a tapping attachment, or use the drill press as a tap alignment fixture something like this: to keep the tap perpendicular to the hole. If you try it by hand, it might break the tap.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
If we do our own extrusion, it would be different. In the Hammond box, it's hard to access the PCB, especially the boxes that don't have a removable top cover. Even those are a real pain; you have to remove six screws and one of the end plates to slide the cover off.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Cursitor Doom wrote in news:pgok6i$8ib$21@dont- email.me:
At that point it is actually "knurling". Something usually done to automotive valve guides.
"Carl Ijames" wrote in news: snipped-for-privacy@news2.newsguy.com:
No... it doesn't. It has plenty of compression.
But anyway... these guys are the masters...
"Carl Ijames" wrote in news: snipped-for-privacy@news2.newsguy.com:
Yeah... they did not believe Howard Hughes either when he said that fluids ARE compressible.
Anyway, without it being a cylinder, and therefore not able to be simply drawn from a tried and true guide, the best seal will occur after a couple design/adjustment cycles, because it still uses the same principle as a cylinder/piston seal.
"Carl Ijames" wrote in news: snipped-for-privacy@news2.newsguy.com:
No... it doesn't. It has plenty of compression.
But anyway... these guys are the masters...
I was asking about the width of the groove, not the depth. It looks like it has about 30% compression (how much the oring sticks up out of the depth of the groove, and too much is also bad), but it looks like there is no room laterally to permit deformation without extrusion as the oring is compressed. If you followed the Parker guidelines as I recommended elsewhere in my post for both width and depth for a gland seal then it should be fine.
-- Regards, Carl Ijames
Plutonium is compressible too.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Cows Are Nice wrote in news:ph3k6g$ta1$ snipped-for-privacy@gioia.aioe.org:
Lasse Langwadt Christensen wrote in news:ed068e9a-9cf0- snipped-for-privacy@googlegroups.com:
It is an 18MB file. What are you running? A 386 with an MFM hard drive? Sheesh. It works fine.
snipped-for-privacy@decadence.org wrote in news:ph3lmv$uus$ snipped-for-privacy@gioia.aioe.org:
A simple online search reveals that foxit has had problems with 3d pdfs throughout its existence. Even abandoning support at one point.
OK, Adobe Reader 9 does the task, with only minimal flakiness. Thanks.
And Zenith http://148.163.81.10:8006/ brings us an hour of Pink Floyd, Saturdays @ 2:00pm left coast time.
Cows Are Nice wrote in news:ph3rb8$179p$1 @gioia.aioe.org:
@gioia.aioe.org:
Zenith is great.
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