Tapping 6-32 in aluminum

wrote:


I've been satisfied with this USB power meter: (Amazon.com product link shortened)FBMV262PJEWDTNA8FE&pf_rd_t 1&pf_rd_p44687642&pf_rd_i0HTAH3KY
I don't remember exactly how accurate it was, and another could be different. It was close enough to tell which USB hard drives would run comfortably off the laptop USB2 port (WD) and which were marginal (Seagate) and should be on USB3 or a powered hub.
I sorta wish I'd bought a dual display meter because the drives can take longer than the Volts / Amps display switching interval to come up and stabilize.
-jsw
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On Tue, 7 Apr 2015 13:33:03 -0400, "Jim Wilkins"

! wasn't talking about the USB one - I was taliking about the higher voltage higher current ones used by the RC plane guys.

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wrote:

Oh, those! I have the 60V 100A AODE model. The voltage is pretty close but the current actually resolves to 0.2A (9 bits?) despite the appearance that it reads to 10mA. It fakes the difference by "dithering", or injecting random noise to make the display bounce around. (Amazon.com product link shortened) "USes DSP to increase ADC resolution ..." But not ADC accuracy.
It's still useful, just not to monitor trickle charging or equalizing. I put Andersons on the 33V, 3A meter for that.
-jsw
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On Mon, 6 Apr 2015 17:31:57 -0400, "Jim Wilkins"

I bought one of those solar wattmeters o eBay for $14 or so and it works well for 12v. The little ones above are USB, so they are for 5v USB circuits only. Since Ig said 5v, I keyed on it.
I forgot to check the charging rate of the little USB wattmeter through the solar charge controller, but will do that tomorrow. (Where the 'ell did I hide the little bastid, anyway?)
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wrote:

I turned the cable and a connector from a USB1 hub into a breakout cable to check the AboveTEK meter with a DVM and an external resistor load.
AFAIK USB2 ports can supply 500mA continuously, for USB3 it's 900mA. They are protected (?) by PTC thermistors that allow higher startup surges. I'm not about to risk my laptops or portable hard drives by measuring these limits.
I run into them with a USB3 ExpressCard that won't run a portable hard drive without externally supplied 5V.
-jsw
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On Mon, 06 Apr 2015 15:28:14 -0500, Ignoramus32423

I checked the charging current from the computer vs. the wall wart charger for my Kindle and the computer was 1/3 the current, taking a whole lot longer. It surprised me, but now I use the wall charger exclusively, unless I'll be at the computer all day.
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I just bought it
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On Tue, 07 Apr 2015 06:48:24 -0500, Ignoramus13314

They're very handy in their niche.
Shipped direct from China ($3/1 month dlvy time) or from the USA ($15/1 week)?
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On Monday, April 6, 2015 at 4:45:22 AM UTC-7, Ignoramus32423 wrote:

It'd be better if you used no tapping at all, just a smaller bolt (#4-40). The force needed to get a #6-32 into an undersize hole can warp the surface (and hurt the heatsinking). It can also make it hard to stop when the torque is 'enough': the copper of the heatsink tab can be deformed, and that makes for a TERRIBLE thermal connection.
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On Sun, 05 Apr 2015 09:30:13 -0500, Ignoramus10114

Have you considered adhesive, even hot melt? Another possibility is drive screws typically used to mount labels on machines. http://tinyurl.com/ov9n6d4 Self tapping? http://tinyurl.com/njbqope suggest rollform [no chips/flakes] square or torx drive.
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In aluminum heat sinks for controllers and drivers I often thread form 6-32.
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On Sun, 05 Apr 2015 07:59:56 -0500, "Lloyd E. Sponenburgh"

Both are the same pitch, 32tpi, Ig. So what's your real question?

Yeah, original posters, please don't say what it's _for_. <sigh>
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PS... a lot of heat-sink _component_ mounting hardware comes in M2.5x.45 size, for mounting things like TO-3 and TO-220 packages. That's smaller than 6-32.
L
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On Sunday, April 5, 2015 at 5:47:16 AM UTC-7, Ignoramus10114 wrote:

Either would work, assuming the aluminum is thicker than 1/16 inch.. you never want less than two threads. Be sure to check/flatten the machined surface (I sometimes rub it down with a whetstone) if there's any deformation, or the flat-to-flat heat transfer interface will be compromised.
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That would truly be a sin on a nicely anodized heat sink!
If it's not flat, it's junk anyway, I guess.
Lloyd
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On Sun, 05 Apr 2015 07:47:14 -0500, Ignoramus10114

Both are 32 threads per inch, so how is one "less course"?
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Because of bigger diameter.
i
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On Mon, 06 Apr 2015 08:13:53 -0500, Ignoramus32423

A couple of minor points: You can tap aluminum to a higher thread percentage than steel, because it takes so much less force to cut. But there's little advantage to cutting deeper than 70% depth in any material.
And two, if you have any old Tapmagic lying around (we who have it hoard it like it's fine whiskey), don't use it on aluminum unless it's the version that says "aluminum." It will boil and form a foul, black gummy mess as it eats your aluminum for lunch.
Oh, and one more thing: "coarse" is not "course." d8-)
--
Ed Huntress

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Ignoramus10114 wrote:

6-32 works fine. I do these often. A good, sharp tap (not the horrors from the local hardware store) work quite well. I use "Alum-Tap" from Wibro as a tapping fluid, it is incredible stuff. Makes the tap go in like it was already threaded.
Jon
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Oh, I don't know... if I want a 'standard' straight-fluted tap without having to wait, Hansons are pretty good quality. 'Never got a dull one, nor one not accurately-cut. They cut freely and don't leave any more burrs than any other reasonably well-made tap.
I prefer spiral-flute taps for most work, because about 3/4 of my stuff is blind holes; but there's nothing wrong with a Hanson tap. That's what ACE carries - carded, one per. I don't know about your local hardware store.
LLoyd
LLoyd
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