On 2008-01-01, wrote:
I've got blisters on my hands from taping 20 holes manually and I have
hundreds left to go!
What machine or tools do I need to tap 5/16th-18 holes in aluminum? I
am using T slotted 1.5" square tubular aluminum for a lot of projects,
ranging from a workshed to a photobooth to a workbench and having to
manually tap the ends of this metal is going to kill me!

You're tapping the ends. How long are the pieces? Short enough
to fit between the base of your drill press and the end of a tap in a
tapping head?

I'm
specifically using http://www.8020.net/T-Slot-1.asp this stuff. I
bought two specialty taps that are a combination drill/tap bit from
www.mcmaster.com part # 2748A43 At $20 each they are pricy and I've
already busted them both after only about 6 holes each with a hand
drill.

A *hand* drill? Yes -- you are pretty likely to break them that
way. They are quite brittle, and it is difficult to avoid putting
side stress on the tap/drill when working that way.

And if you are drilling and tapping the *ends* of these
extrusions, I suspect that these are not through holes. The drill/tap
combinations are made for use in through holes as far as I can tell.
The drill tip has to clear the far side of the workpiece before the
tapping part starts working.

So -- you want a drill (in a drill chuck) followed by a spiral
flute tap to get the chips out -- or even better a rolling tap (thread
forming tap) which generates no chips -- but requires a slightly larger
hole. (Look it up and order the right size drill bits at the same time.
It is likely to be a Metric size. Look up the proper size in
_Machinery's Handbook_.

This would still be better done in a drill press if the
workpiece is short enough. If your drill press table will tilt to the
side, rotate it 90 degrees, and bolt a chuck onto it to hold (and
position) the workpieces. Drill them all, then change out the drill
chuck for the tapping head and go back through tapping under power. Be
sure to get the proper lubricant for the roll taps. But they will form
stronger threads in your aluminum than the standard thread cutting taps
will.

Now if you consider the drill/taps expensive, you *won't* like
the new price of a tapping head. But they can be found somewhat more
affordably on eBay -- given patience and luck. I got the smaller of
mine (TapMatic) from eBay -- and the larger from someone else at a local
metalworking club meeting.

Any help please?

You have my opinions above. Now to see what others have
suggested.

Good luck,
DoN.

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