tapping aluminum?

[indoorsoccerfrea]

Is it possible to use a steel bolt (taper it, fire-harden it) to tap aluminum? I'm assuming it will work to some degree, but how much? I'm curious to see if anyone has tried it.

 

[Scrapperz]

You can do it but you wont get full thread. I have actually done this as a last ditch effort on machines, Drill, Tap, Drive the bolt tap home and be done with it.

 

[7X57chilmau]

I've successfully done it a number of times, in a pinch... I use a cut-off wheel in my dremel to cut a notch in the first few threads of the bolt, like a self tapping screw tip.... And will often taper the first few (usually 3) threads on a bench grinder first, to ease starting....

If you have a high grade steel bolt, this can also be successful in mild steel too... With much care, much lube, and much backing out to clear cuttings.... But yes, it can work.

J

 

[rcmodel]

Why bother when you can buy a real HS steel thread tap at any hardware store for a couple of bucks?

rc

 

[rmfnla]

Actually, I prefer to do it the way the OP suggested.

Instead of cutting the threads you are essentially forming them, and work-hardening the aluminum at the same time.

 

[whiskey3]

I agree with rcmodel. The right tool for the job is the best way to go.

If you do use a bolt starting the threading cleanly and square will be difficult. Make sure you have good threads or else the thread depth in the hole will not be correct and you will risk breaking of the hardware. Taper taps spread the cutting job out over a larger area than bottoming taps (or your bolt) and stay sharp longer. Bottoming taps dull quickly when used for hole tapping so be aware of your threading and use copious amounts of cutting fluid!!

 

[indoorsoccerfrea]

rcmodel, the reason I don't want to buy the tap I need is because it is around $60...
I need the buffer tube tap for an AR-15 lower and was thinking about all my options before I sprung and bought it...which I would like to avoid if possible.

 

[HankC]

delete

 

[Scrapperz]

http://www1.mscdirect.com/cgi/nnsrhm

Try this place maybe they have the tool at a reasonable price. Worth a try anyway.

 

[Owen]

Try renting the tap? A thread that big is really something I'd want to do on a machine. Straighness is critical. If its angled the carrier will bind.

 

[navyretired 1]

In the long run the tap is a cheap investment. You can always sell when your finished if you don't need anymore?
BTW before the flutes are cut in a tap it looks a lot like a "bolt" (kinda), but I would recomend for extention tube threads on an AR platform. I finally made a jig to align the threads as all the aligning would cause 1/2 the threads I needed and that was with the proper tap.

 

[Zeke/PA]

Large tap?
A tap made from a corresponding bolt?
You are asking for trouble.
I your use is a mere screw/ bolt type issue, its one thing but, somehow I get the feeling that it is more than that.
Think out you issue as a bad tapping job can surely spoil your project.
It won't hurt you on this forum to elaborate!
Respectfully, Zeke

 

[rcmodel]

Screwing a 1-3/16" -16TPI bolt in an untapped AR-15 lower would most assuredly result in a cracked and/or ruined lower receiver.
Don't even think about it!

rc