Dumb question about taps for helicoil inserts.

plutoniumsalmon · Apr 7, 2019

Howdy.
I have to make a bunch of 4 40 holes for a 4 40 hellicoil. Do I use the same feeds and speeds as I would for a normal 4 40 tap? I need the same pitch, right?

Finegrain · Apr 7, 2019

Yes, same feed. I guess if you were wanting to hit a specific SFM for tapping you would slow down a little compared to regular 4-40. Bigger drill size of course :-). Helicoil website has charts for proper drill size.

Regards.

Mike

plutoniumsalmon · Apr 7, 2019

Finegrain said:
Yes, same feed. I guess if you were wanting to hit a specific SFM for tapping you would slow down a little compared to regular 4-40. Bigger drill size of course :-). Helicoil website has charts for proper drill size.

Regards.

Mike

Thank you.

Delw · Apr 7, 2019

if your doing these per a spec make sure you use a 120º chamfer otherwise your will get rejected chamfer dia for 4-40 STI .140-.170
I have best luck with a .122 drill or 3.1mm metric. we do thousands of 4-40 STI threads

heres a chart also
Helicoil Screw Thread Insert (STI) Tapped Hole Dimensions

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Dumb question about taps for helicoil inserts.

plutoniumsalmon

Hot Rolled

Finegrain

Diamond

plutoniumsalmon

Hot Rolled

Delw

Stainless

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