Tapping aluminum

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Ned Payne

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I have a piece of aluminum that is .531" thick it is a piece of quarter panel moulding i had made. I need to tap holes to secure the moulding. Is there a minumn depth to drill then tap the hole so it is secure?
 
tap it as fine TPI as you can. 1/2 inch AL as a trim? Gnarly! Rule of thumb is min depth should equal diameter of screw. 1/4 diameter screw needs 1/4 depth.
 
Depends...what size bolt/screw and what thread pitch, fine/course.
 
I go course on something like that, the thread goes deeper into the soft material and holds better than fine.
 
Whatever you are taping need to have at least 3 threads to hold. It's better to have at least 5 but 3 is all that actually hold the part.
 
pishta said:
tap it as fine TPI as you can. 1/2 inch AL as a trim? Gnarly! Rule of thumb is min depth should equal diameter of screw. 1/4 diameter screw needs 1/4 depth.
Click to expand...

WHEN IN ALUM. , I LIKE WAY MORE THREADS BECAUSE OF THE SOFTNESS OF THE MATERIAL -
 
famous bob said:
WHEN IN ALUM. , I LIKE WAY MORE THREADS BECAUSE OF THE SOFTNESS OF THE MATERIAL -
Click to expand...

In trim he's probably going to need a #8 screw, so the threads of a 8-32 will pull out easier than a 8-24 because it has a better bite on the aluminum.
 
There are different types of drills and taps that will get you full threads to the bottom of the hole.
 
We need pictures of this badass molding you made.
 
I would not use "screws." Use studs even if you have to cut down screws, loctite them into the molding, and nuts on the inside. I would not use steel either, maybe brass or stainless

As redfish pointed out, there are several kinds of taps. You can "lightly grind" a bottom tap to get a bit "closer." So you might want to buy two bottom taps
 
The stud idea is a good one. You need to be careful when drilling and tapping what we call a blind hole. You can use Loctite 609 to hold the stud in.
 
I agree with studs and fine threads. WD-40 works well for me when tapping aluminum along with a good sharp tap, I prefer two flute over three, especially on small taps, although on aluminum it probably wont matter.
 
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