Tapping 6-32 in aluminum

I have an aluminum heatsink that I need to tap , I wanted to know if I should use 6-32 or some less coarse thread like 8-32 would be better?

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What's the application? The 8-32 would be a stronger bolt, with more thread cross-section. But it may not be necessary for whatever you wish to hold.
L
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On 2015-04-05, Lloyd E. Sponenburgh <lloydspinsidemindspring.com> wrote:

strength not an issue
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Then one sizes it according to what you want to mount.
I mentioned 2.5x.45 metric... some also use 3 x 0.5mm, but even that's smaller than 6-32.
If you need to mount through screw insulators (like for mounting a transistor or a floating-case regulator like an LM-317, you may be hard- put to find any insulators that will fit even 6-32... metric has more-or- less filled that market.
Lloyd
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On Sunday, April 5, 2015 at 10:34:56 AM UTC-4, Lloyd E. Sponenburgh wrote:

With a rapidly expanding international market where demand for metric outstrips demand for trade (in everyplace but the US), its not surprising.
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On Sun, 5 Apr 2015 09:30:11 -0700 (PDT), walter snipped-for-privacy@post.com wrote:

That has little to do with it. Except for construction and transportation equipment, it's mostly a matter of whether the industry is heavily involved with science, in which case US fasteners are metric fasteners, just as they are everywhere else, or if it has an international supply chain.
It's useful to look at three markets: the market for off-road equipment (mining, construction, etc.); the market for automobiles; and the market for electronic devices.
In the first case, the issues are that the market is truly global and that the equipment has to be repairable around the world. Thus, Caterpillar was the first large US company to go 100% metric, beck in the '70s.
In the case of automobiles, US-built cars have never had much of a global market but they are now the end of a global *supply chain*. It is cheaper, and more flexible, to use metric fasteners for US-built cars, when they may be built from parts supplied by 20 different countries.
Electronic devices are designed and built in an environment that is close to the underlying science, where metrics have been the lingua france in the US for most of a century. Metrics are followed in the engineering and in the assembly; repair is a miniscule economic issue. Also, the supply chain is not only multinational, but also ad hoc; you may not know this week where your parts will be coming from next week.
The upshot is that, with 70% of our economy based on domestic consumption, there is little or no economic advantage to making sweeping changes to metrics in other industries. Thus, change is slow. And it has little advantage for anyone other than those industries described above.
--
Ed Huntress

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On 4/5/2015 1:40 PM, Ed Huntress wrote: <SNIP> > The upshot is that, with 70% of our economy based on domestic

70% of every product purchased in the U.S. is made in the U.S.? Wow, I didn't think it was that high.
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wrote:

70% of our GDP is domestic consumption. That's net of imports and exports.
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Ed Huntress

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On 4/5/2015 3:47 PM, Ed Huntress wrote:

Ahhh. I misunderstood/misread as consumption of domestic goods. Is there a doG? <G>
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wrote:

The dollar percentage of durable goods sold in the US and made in the US was 66.6% in 2010. The overall percentage of dollar value of consumer imports, in all categories including oil, was 11.5%, of which the actual cost was 7.3%. The remaining 4.2% goes to US transportation, wholesaling, and retailing markups.
If you follow US manufacturing and trade for a decade or more, you'll realize that almost every popular conception about our manufacturing and trade is wrong.
http://www.frbsf.org/economic-research/publications/economic-letter/2011/august/us-made-in-china/
--
Ed Huntress

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On 4/5/2015 6:10 PM, Ed Huntress wrote:

Thanks for the followup. Very informative.
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wrote:

Sure, Steve. It's easy to develop a completely wrong impression about our trade situation.
BTW, that research piece by the Fed is one of the few you'll see that analyzes the foreign-made components of products assembled in the U.S. It's not easy to measure, and off-the-cuff estimates are all over the map. This one looks like it was done right.
--
Ed Huntress

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6-32 is a course, ie nc, thread. 8-32 is a fine thread, ie nf. The fine threads do less cutting relative to the screw's major diameter. The 8-32 will be less likely to break than the 6-32 which, in steel, is a consideration. In aluminum probably either one would free of worry. Maybe the 8-32 would be a little freeer.
Hul

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On 4/5/2015 6:42 PM, Hul Tytus wrote:

"8-32 is a fine thread, ie nf"
No, 8-32 is UNC.
MikeB
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So it is. Thanks for the correction. The difference between 6-32 & 8-32 remains as stated, though.
Hul

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wrote:

I've always considered 32tpi to be "fine", too. I guess there are 6-40 and 8-40 threads for the fine side, though I don't recall ever seeing one so far in this lifetime.
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I learned something cool, I do not need to tap anything! If I drill a 1/8" hole, a 6-32 screw taps it for itself very nicely.
i
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Not really, Ig. If your 1/8" drill made an accurately-sized hole, it would be a VERY slight threadform.... .1380 in a .1250 hole only leaves about 7- thou of thread engagement. Unless it's only decorative AND the 1/8" drill is tuned up and used right, that's a 'barely holds' situation.
The called-out tap drill is #36 (0.1065), meaning about 16-thou of thread engagement, when done right.
Lloyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> fired this volley in

ps... that's all at the 'imaginary' fit of 100% threadform. It's less in practice.
Lloyd
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On 4/6/2015 11:20 AM, Lloyd E. Sponenburgh wrote:

1/8" is the specified hole diameter for roll tapping a 6-32. Admittedly, running a screw in, is not exactly proper thread forming, but in some situations, should work OK, if loads are low and servicing not likely. Just as much a factor I'd think, is the probability that the screw crest will deform due to not being hardened, and I believe this more than the hole size would reduce the strength.
Jon
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