[BAD DOG]

WE MACHINE A TON OF PARTS ON THE LATHE THAT GET A 1/4-18 NPT FEMALE PIPE THREAD IN 5/8 316 SST HEX. (CNC LATHE)

HAVING TROUBLE GETTING INSERT LIFE.

WHAT ABOUT USING A TAP.

ANY HELP?

BAD DOG

[g-codeguy]

Good luck with that, friend! We have basically given up on that size thread in that material. Cost is too high. We tap as a secondary.

I certainly would like to know if you do find a combination of insert, RPM. DOC, etc. that does work. Bet plenty of other inquiring minds would like to know also.

[BAD DOG]

I WAS ALSO THINKING AS A SECOND OP,,, WE DO A LOT OF THREAD MILLING AND THAT MAY BE THE WAY TO GO

BAD DOG

[One of Many]

Have you tried these?

Besly spiral


Dormer also makes some

Don't know if it would help to cut the hole tapered before tapping so the tap has less to remove. I have heard that these help retain tapping oil like sulpher based cutting oils to prevent material buildup. Might be worth a try in high production where the increased through put pays off better than single pointing.

DC

[RMDMARINE]

BAD DOG

In our (my son and I) business we manufacture marine hardware and use a lot of 316l S/S and tap a lot of fuel and oil manifolds. We have found the best way, is to drill and taper reamer for the NPT size and use stagger tooth taps with a high Sulfer base cutting oil, you need the sulfer for lubricaton since 316 has more soft Nickel and will gall.

If I was doing it on a CNC Lathe I would drill base hole and then run a NPT taper reamer then single point the hole.

It also helps if you ream to the max pitch diameter.

Bob

[g-codeguy]

BAD DOG

In our (my son and I) business we manufacture marine hardware and use a lot of 316l S/S and tap a lot of fuel and oil manifolds. We have found the best way, is to drill and taper reamer for the NPT size and use stagger tooth taps with a high Sulfer base cutting oil, you need the sulfer for lubricaton since 316 has more soft Nickel and will gall.

If I was doing it on a CNC Lathe I would drill base hole and then run a NPT taper reamer then single point the hole.

I prefer to single point anytime I can. Only problem single pointing a 1/4 NPT is there is no place for the chips to go. Inserts won't hold up.

It also helps if you ream to the max pitch diameter.

Bob

I assume you mean max bore.

[djr76]

Use an OSG VA3 tap or SS specific tap and rigid tap it, be much faster then single pointing that small.

[StephenBorst]

If you got the skills grind a little more relief on the backside of the tip of the insert try around 15 to 20 deg. I had chip clearance issuses and that helped. Also try .002 to .003 D.O.C. per pass. And if you can richen up your coolant to 20%

[PixMan]

If using the full-form inserts as I suggested, grinding a relief is not possible nor advisable. The only adjustment is the shim seat under the insert which must be matched to the lead angle of the thread. The smaller boring bars and external threading tool holders may not have the interchangeable shim seats, but their smaller inserts are thinner and made with the side reliefs at high enough angles to handle almost any thread lead angle. (The lead angle increases as the diameter shrinks if given the same number of threads per inch/mm.)