# Aluminum threading help



## Stevej72 (Nov 20, 2011)

i started on a closed end aluminum pen today.  I got the cap shaped and threaded.  The body and the tip piece (not sure what you call it on a rollerball) are drilled and I threaded the inside of the body and the end of the tip so the screw together nicely, although the threads look a little coarse but that is all I had that would fit.

My problem is threading the outside of the body so the cap will screw on.  I bought the tap and die 2 or 3 years ago on a group buy and have never been able to thread with the die.  I've tried acrylics several times over the past couple years and today I tried the aluminum.  When I take the die off all of the thread have been torn off.  Not sure what  I am doing wrong.


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## AlanHil (Nov 20, 2011)

*Threading problem*

I was a machinst for 13 years and that would sometimes happen when hand threading softer metals. The solution is to get a Swiss-type multi-axis machine like this that does more than one operation at a time.
http://www.youtube.com/watch?v=hjVXbEUZJJs&list=PL283E3FDF9AA3CA35&index=18&feature=plpp_video

Barring that, it looks like it's cross-threaded. It could be a bad die, I've had that happen once. But try using a good quality cutting oil. If you are threading it in a lathe, use the tail stock to steady it. You might also try backing up and breaking the chip every half turn. 

It might also be bottoming out against the work. 

Good luck.


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## Stevej72 (Nov 20, 2011)

Thanks Alan,  I guess I should have posted my procedure.  I mounted the die in a holder and put it in the drill chuck on the tail stock end.  Then I put pressure on the tail stock (toward headstock) while turning the chuck on the headstock of a metal lathe.  I did back up a little every little bit, not really sure how far I turned before I backed, but less than a full revolution.


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## BigShed (Nov 20, 2011)

Have you used a good cutting oil for aluminium?

Makes a world of difference to threading on most materials, I use Trefolex on steel, cooking spray on acrylics and Relton A-9 for aluminium.

In addition, make sure you remove swarf regularly, if necessary by going back all the way and blowing swarf out of die with compressed air. Sometimes aluminium swarf can really get stuck in a die and it will be necessary to remove it with a sharp pick or something similar. Continuing with the swarf stuck will ruin your thread.

If in doubt, withdraw and lubricate, repeat as necessary.


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## cnirenberg (Nov 21, 2011)

I found this out the hard way so I'm not ashamed to ask.  When you threaded the tenon and inserted the die in the holder was the side that has the writing (size etc.) on the outside of the holder?


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## PTownSubbie (Nov 21, 2011)

Are you using a Carbon Steel (less expensive) die or are you using a High Speed Steel (HSS) die?

I got the same results using a cheap Harbor Freight die and when I used a better quality die from Victor Machinery, the results were perfect.....

Just a thought.....


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## studioso (Nov 21, 2011)

having had more experience stripping threads than producing good ones, I would wonder if you turned the diameter small enough. aluminum probably needs a smaller D than plastic (IAP gods, please confirm that). so either turned the shoulder down a bit more, open the die (if it's adjustable)


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## PenMan1 (Nov 21, 2011)

A little tip I learned from George (Texatdurango) for threading acrylics, works equally well or better on aluminum.

George taught me to slightly chamfer the leading edge of the threading. This helps the die get a "little bite" on the material and helps reduce cross threading (that's what your photo looks like, to me).

And to the question about material reduction, I have found the "need" to remove a little more material from an aluminum body than from other materials. This allows me to put less pressure or 'force" on the tailstock and keeps it running accurately.

THIS IS NOT a definative answer as I still "misthread" often, it simply is the best answer in my shop.


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## PenMan1 (Nov 21, 2011)

Another plug for George.  I have found TWO resources in the library that I use almost daily.

The first is Wayne's chart on tube sizes and bushing sizes (and REALLY not relevant to this post). The second is Texatdurango's "another way to make a pen" tutorial. This post is photo intensive and a good study that I always go back to when I encounter issues with making "non-standard" products.

I hope this helps.


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## Stevej72 (Nov 22, 2011)

Thanks everyone.  I wasn't sure which way to put the die in the holder so I will make sure that the writing is out.

Don't know if it is carbon steel or HSS.  The 3 start tap and die cost over $100 together so you'd think it would be good steel.

I looked at the tutorials and  am going down to the shop now to try again and will add a chamfer to the leading edge and make sure the die is in correct.


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## PTownSubbie (Nov 23, 2011)

Stevej72 said:


> Thanks everyone. I wasn't sure which way to put the die in the holder so I will make sure that the writing is out.
> 
> Don't know if it is carbon steel or HSS. The 3 start tap and die cost over $100 together so you'd think it would be good steel.
> 
> I looked at the tutorials and am going down to the shop now to try again and will add a chamfer to the leading edge and make sure the die is in correct.


 
If it is the triple start, I missed that. It is fine for the aluminum if that is the case.....

Yep, check the die. There is a slight taper to one of the sides that makes starting of the threads easier. Also, don't put a ton of forward pressure on the die, let it move forward with the threads. I have placed too much pressure on it with resin and striped the threads....I wouldn't think that was possible with the aluminum though.

What size tenon did you start with?


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## workinforwood (Nov 23, 2011)

I do not bother with cutting oil on aluminum hand threading. There's just a few little tricks.  The OD of what you are threading must be exact or slightly less than the die size. So for example, a 12x1 die would require a 12mm tennon. Make the tennon be 12 mm or 11.95 mm, but not 12.1 mm. Only the teeth can cut, not the flat beyond the teeth or you will be taking off too much meat and the material is too soft to handle that. Rule #2 would be to go very slow, have tons of patience. A 12x1mm die threading a 1/2" long tenon may take you 20 minutes to thread. That's a meaty die, so you would only enter an 1/8th of a turn while pushing in on the tailstock at the same time, then have to back off and clear the threads for your next 1/8 turn. It's a lot of work. From what I see in the pic, the threads on the success are real meaty, so you have to feed those super slow and the larger the OD, the slower you will need to go.  I do assume you are using a lathe to do your threading..like you hold the part in a collet and use the tailstock to hold your die and pull them together as you spin the collet by hand. That's basically what I would do..so you have control and alignment.


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## Stevej72 (Nov 23, 2011)

Thanks Fred,  I tried some different tenon diameters, but about 12 mm  is me most recent.  Earlier tests were slightly less than that.


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