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Camdude®

FEEDS & SPEEDS FOR 1/8-27 NPT

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I have to tap afew holes in 1018 using a 1/8-27 NPT tap. Doesanyone have a good feed and speed range for this tap. normally i would thread mill it but TPTB's don't want to do that so i'm stuck tapping.

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It depends if you are using oil or coolant (water based) and what type of tap and machine as you must have the power at low rpm. If coolant and standard tap and machine, I usually go slow. Something in the range of 10-15sfm would be fine. It's about 40% of what the book (OSG) would say. By the way, I always recommend tapering the hole using a taper pipe reamer or 1-1/2 deg em. This makes for much easier tapping and less chance of tap failure.

 

Mike

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quote:

tap failure

aka...POW!

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As said above, an NPT Reamer helps out alot.

Interrupted tooth taps seem to be better also (just from my own experience).

Try it at about 400 rpm's and see what the threads look like.

But overall, I've never had the best of luck tapping npt's on a cnc for some reason, the threads like to tear about 50% of the time.

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"the threads like to tear about 50% of the time."

 

1018, 50% may be an understatement... you say just a few holes, I'd just go deep enough to get them started & finish by hand.

 

cutting oil will be much better than coolant IMO.

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quote:

just go deep enough to get them started & finish by hand.

Another good thing about using an npt reamer is that it's way easier to start the tap by hand, if you don't start it on the cnc, provided that you take the reamer to the correct depth and let it chamfer the hole.

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I know you don't want to thread mill, but if you tap by hand, at the point that you stop there will be a vertical line up the flanks because it's cutting on the full engagement of the tap (unlike parallel tapping where it's only at the bottom/start of the tap).

We couldn't get around the line whatever we did (different oils/taps etc), so had to end up thread milling.

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REMEMBER....stop 1/4 turn before it breaks and you'll have no problems. biggrin.gif

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lol@Odell,

thanks guys gives me a start point,

like i said i WANT to threadmill but the powers that be do not>>>> mad.gif

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Use a good rich mix on your coolant or use tapping fluid if possible and peck tap if you have that capability. cheers.gif

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We run npts at my shop all the time. On a 1/8-27 i go 300 RPM 11.11 IPM and Z-.350 deep and we use tapping fluid

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Tapping oil +++ , coolant works sometimes depending on what coolant you are using. Using both won't hurt. Definatly use an interrupted tooth tap as others have said.

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