[time-nuts] Machining some aluminum help!

djl djl at montana.com
Fri Jul 28 16:27:58 EDT 2017

Good even for mild steel too. Best is your good advice to use the drill 
press to keep the tap aligned.  softer aluminum alloys are very "sticky" 
and demand backing off a turn for almost every turn forward for cutting 
taps to break the chip. I've found that the 6/32 tap is the most easily 
broken. sigh.
Pay attention, the tap drill is not the same for the forming tap as it 
is for the cutting tap.

On 2017-07-28 13:46, cdelect at juno.com wrote:
> Well I did some research and found my new best friend!
> If you remember I needed:  "I have a square aluminum tube 5" X 5" with 
> a
> .25" wall it's 8 1/2" long.
> I need 20 holes in each end tapped for 4/40 and 1/2" deep."
> This for a Rubidium standard I am working on.
> I found all about self forming taps!
> I drilled the 20 1/2" deep holes and then made a handwheel to attach to
> the pulley on my drill press. After mounting the tap in the drill press
> and putting a dab of Crisco on the tap I was able to tap each hole to a
> depth of 7/16" as fast as I could turn the handwheel!
> I then got another 8-32 self forming tap to do the holes for 15 
> feedthru
> capacitors, again as fast as I could turn the handwheel.
> I'm very happy to discover these taps!!!!
> Cheers,
> Corby
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Dr. Don Latham
PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304

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