[t_chance]

The last time I had this job I went thru 3 taps (broken teeth) on ten parts.
I tried drilling oversize, big chamfers, down to 15 SFM. Nothing seemed to work.

I just got them again. HELP
I don't want to do them by hand.

HAAS VF3

[extanker59]

Years ago I ran 1/4" NPT in 303 stainless. I used a tapered mill to get the correct taper before tapping. I also had a M00 to apply thick tapping fluid before each hole. I don't remember going through taps but it was years ago.

[LeeWay]

What is the material? What kind of holes? What size and depth of holes? What brand and style of taps were you using? What speed were you tapping at?

[t_chance]

REGAL BELOIT, SOME "WHO KNOWS WHAT" 5/16 304 BAR
The last time I had this job I went thru 3 taps (broken teeth) on ten parts.
I tried drilling oversize, big chamfers, down to 15 SFM. Nothing seemed to work.

[t_chance]

CUTTING LUBE
RIGID EXTREME PERFORMANCE THREAD LUBE

[LeeWay]

I assume you mean NPT. I think you need to have the perfect recipe of hole size, speed and depth to pull this off in a machine without breaking taps. I don't think I have ever seen a machine tap for an NPT thread. I am sure they make them, but I would not want to see the cost.
I did see these at McMaster Carr, but they are still intended for hand tapping.
https://www.mcmaster.com/2663a43

Not cheap either.

[Jim Dawson]

304 is a PITA to work with. Maybe a thread forming tap would work? http://balax.com/sites/default/files...-Pipe-Taps.pdf

[t_chance]

REGAL BELOIT, SOME "WHO KNOWS WHAT" 5/16 304 BAR
The last time I had this job I went thru 3 taps (broken teeth) on ten parts.
I tried drilling oversize, big chamfers, down to 15 SFM. Nothing seemed to work.

NOW 3/8 THICK NOT 5/16

[t_chance]

OTHER TAPS WHERE OSG ELECTRALUBE AND REIFF & NESTOR

[djm77]

Why not thread mill it?


Sent from my iPhone using Tapatalk

[Machineit]

Pipe taps do not clear chips easily, so I would use 4 or 5 steps to do it. Decreasing amount of cut for each pass. Oversize holes for sure, as the standard for hand tapping has the tap cutting the sides walls way too much.

[bhurts]

I have tapped a ton of npt threads in ss. I have had trouble with thread tear out of threads but I don't think I've ever broke one. I use taps like these.

https://www.regalcuttingtools.com/pr...aper-pipe-taps

I set the rapid low. Just as the tap reaches the r plane and starts spinning I add a heavy dose of tap heavy from a oil gun. I follow the stream up the tap to the height of tapping depth. In the other hand I keep the air hose. As the tap is retracted I blow a constant stream of air directed at the entrance point of the hole. This usually results in a clean tap you can follow right to the next hole and repeat. If there are chip that don't come off I feed hold and remove before it starts spinning again at the next hole.

Ben

Sent from my E6810 using Tapatalk

[t_chance]

Thanks Ben.
That was the problem, packing chips. My taps never snapped off, just chipped out the teeth. I'll give those a try.
Tom

[generaldisarray]

Threadmill. costs the same as two pipe taps, lasts a long long time, makes beautiful threads that gage perfectly.

[JFettig]

Definitely thread mill.

[Matt@RFR]

4th vote for thread milling. Stop banging your head against the wall.

[t_chance]

POINT TAKEN.
I've banged my head against the wall for too many years. THANKS

The boss wouldn't spring for anything more than a hand tap. He's a welder...