# Threading aluminum



## Displaced Canadian (Jun 4, 2012)

I'm trying to thread the inside of a piece of 6063 aluminum and it's not going well. I'm using a 10x1.5 tap and using oil and going a 1/4 turn and when I turn it back to clear the tap out it jams up and destroys the threads. I even drilled the hole 1/64 over and am having the same issue. Any thoughts?


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## kruger (Jun 4, 2012)

the hole is 10mm - 1.5mm = 8.5 mm


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## ctubbs (Jun 4, 2012)

Christopher, the very best aluminum threading lube I have found is a magic compound of H and O in the formula H2O.  Alright, I am still a smart alack, water.  It cools the metal and allows the threads cut to stay where they belong.  As always, YMMV.
Charles


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## rherrell (Jun 4, 2012)

You might try using 6061 instead of 6063. 61 has alot more tensile strength and it's alot harder, 63 is kind of gummy. 61 is what they use to make machine parts and trailers, 63 is what they use to make extruded parts like window frames. :wink:


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## mredburn (Jun 4, 2012)

What size did you drill the hole?  Plug or taper tap and not a bottoming tap I take it. IF your not even getting the threads started youmay need to drill your hole even larger.


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## Rich L (Jun 4, 2012)

rherrell said:


> You might try using 6061 instead of 6063. 61 has alot more tensile strength and it's alot harder, 63 is kind of gummy. 61 is what they use to make machine parts and trailers, 63 is what they use to make extruded parts like window frames. :wink:



I'd do that, too. Machinability of 6063 is not rated very high.

Assuming your hole is the right size and you're using a taper or plug tap you _might_ try going in at least a full turn at the start before you try to back out. You don't need to back out any more than 1/4 turn. In other words, you might try to keep going forward. I use stuff called Alumicut or Cool Tool - whichever I can reach at the time.

Let us know what works.

Cheers,
Rich


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## BKelley (Jun 4, 2012)

I agree with all, I'd use 6061 T-6 or even better 7075 T-6.  As for lube, I use just plain ole kerosene.

Ben


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## Paul in OKC (Jun 4, 2012)

WD40 has been used for aluminum with good results.


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## Displaced Canadian (Jun 4, 2012)

I drilled the hole 11/32 which works out to 8.7 mm. I do have some 6061. I'll give it a try tonight.
 I understand you subtract the pitch from the overall size to get drill size. Is there a formula for what size to turn a tenon before threading? The tenon was originally turned to 10 mm but wouldn't thread until I turned it down to closer to 9 mm. The post is a clear materiel with a ribbon in it. Not exactly sure what it is.


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## mredburn (Jun 4, 2012)

If you have to move on to another piece drill the first one with an S drill bit and see if that will work. We have had metric taps that don't always follow the rule of thumb. I usually turn the tenon .2mm smaller than the called for diameter. Itf the material is really soft and will stretch .3mm smaller. I would start with 9.8mm for the tenon with a 45 degree starting taper.


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## Paul in OKC (Jun 4, 2012)

Yes, diameter of thread minus pitch will give you a hole size for aprox. 75% threads. OD should be no bigger than stated diameter.


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## Sylvanite (Jun 4, 2012)

This may sound crazy, but what brand of tap are you using?


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## Displaced Canadian (Jun 4, 2012)

I bought my tap and dies from NAPA, 
I used a piece of 6061 and it threaded just fine. I did however change to a 3/8x24 nf tap. The 6061 does seem a lot harder to turn than 6063. Almost tempted to try the fine thread tap is the 6063 because it is easier to turn, but I'm guessing if it is harder to turn it should stand up to more abuse.
 As for tenon size, I think I may need to taper the leading edge a little more for the die to start.
 Thanks for all of your help.


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## Sylvanite (Jun 4, 2012)

I don't know what quality taps and dies NAPA sells, but I know from experience that some brands are worthless.  The harbor freight set I have won't thread aluminum at all.  It just smears.  The ones from Hanson, however, cut great.

Regards,
Eric


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## djknisle (Jun 5, 2012)

you might try lubricating the tap with beeswax


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## Displaced Canadian (Jun 11, 2012)

Sylvanite said:


> I don't know what quality taps and dies NAPA sells, but I know from experience that some brands are worthless.  The harbor freight set I have won't thread aluminum at all.  It just smears.  The ones from Hanson, however, cut great.
> 
> Regards,
> Eric



Just to follow up, I had some craftsman dies that gave me a lot of grief, I bought a replacement from NAPA and it works much better. It is true that not all dies are created equal.


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## yort81 (Jun 12, 2012)

Chris.... are you getting the taps and dies from "our" NAPA dealer on State Street??

And if so... do they have a fairly good selection?

Troy


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## Displaced Canadian (Jun 12, 2012)

Yes I am and Yes they do. They have standard and metric in coarse and fine thread. The best part is you don't have to buy a set and they have both the taps and the dies. Prices are reasonable too.


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## Paul in OKC (Jun 12, 2012)

Most of the auto store type tap and dies sets will be carbon steel. Good for rethreading a bolt or nut, but near worthless for new threads. I have had sales people tell me the theirs is lifetime guarantee, including a fellow co-worker insisting we try Snap-On because they were life time. I told him know way because they wouldn't be able to keep us supplied. He gave me a funny look and ordered some anyway. First use broke teeth off. I got it replaced and they sat in a drawer for a couple of years, then I traded them back to the Snap-On guy for something we could use. For good stuff it needs to be HSS. Even in plastics I wouldn't use the carbon stuff.


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