1/2 - 13 TAP - 6061 Aluminum (Rigid Tapping)

[RJS100]

I am getting ready to tap a few 1/2-13 threads, 1/2 inch deep in 6061 aluminum. My converted benchtop mill has 2.6KW servo motor powering the spindle. The spindle can provide significantly more torque than is required to tap these threads. For some reason, I thought I read somewhere that a 1/2-13 thread should be done with thread milling, and not rigid tapping.

Is this true? Can I tap these holes with rigid tapping?

Richard

[suntravel]

Should be no problem to tap.

Uwe

[RJS100]

THANKS!

[RJS100]

Opps. The spindle servo stopped dead in its tracks. I got a servo fault and can't imagine why. The pilot hole was 27/64". This servo produces 10Nm of torque and 25NM for 3 seconds. Even with a 1:7 pulley ratio, that's still ample torque. Unfortunately, I forgot to read the error code on the servo.

I tapped this hole first with a depth of .300", then to .700". It failed on the second attempt. I am using a spiral flute tap with a bottoming chamfer and H3 tolerance.

Any thoughts?

Richard

[suntravel]

A good tap will need 5Nm for UNC 1/2.

Did you use high pressure lubricant?

TiN coating is not for aluminum, better use a sharp uncoated tap or with ZrN coating.

A drill chuck is als not for tapping, use collets.

Uwe

[RJS100]

Thanks. Most of my other taps have a TiCN coating. I used a mist lubricant. I will try this again with some A-9 cutting fluid I have on hand. The G-Wizard speeds and feeds calculator indicated 333 rpm for this tap. I think this may be too slow. Do you think I should run this faster?

One other question on a similar topic. I buy mostly YG1 Alu-Power end mills with a bright finish. There are some that say Alu-Power HPV 37 degree DLC coated for aluminum (see attached). Will the DLC coated ones last longer? Do you think I should stick with the bright finish?

Richard

[suntravel]

I am tapping a similar metric size in AW7075 with 700 rpm and use a drop cutting paste with high pressure additives.

DLC coating is ok for aluminum, though I prefer ZrN, but even only polished carbide mills will last almost forever in hobby use and they are sharper than coated ones.

Uwe

[RJS100]

Man... You are one handy guy to have around

Thanks for all your insight. I will try this again with your suggestions. Fortunately, I was able to rescue this part and with LOTS of effort, I turned the tap by hand

All the best.... Richard

[Black Forest]

Man... You are one handy guy to have around

Thanks for all your insight. I will try this again with your suggestions. Fortunately, I was able to rescue this part and with LOTS of effort, I turned the tap by hand

All the best.... Richard

Someone is building a belt grinder!

[RJS100]

Yes my friend. What else is a guy to do with an extra motor and VFD left behind from a spindle upgrade... Make a belt grinder. Now I just have to hope that all these pieces fit together when I am done! BTW... I tapped the 1/2-13 again at 700 rpm and some tapping lube and it worked great!