Recommend a tool for 3/4-16 internal thread

[Mud]

We make nuts with a 3/4-16 LH thread. Up til now we've used custom taps. We're wearing out the taps, and we'd like to save the material we waste because of the overly deep thread length needed to allow the tap to cut full size threads in the bar. So we'd like to try single point threading.

Can anyone recommend a bar and insert for this? I have no experience at all in this area. Seems like a small hole to try to stick a bar into to thread. The material is 1144 stressproof. Machine is a 2axis lathe - can't threadmill.

 

[Cole2534]

How deep are you tapping?

 

[plothoundsman]

Sandvik should have a bar and a topper insert , I love those topper inserts , (bur free).

 

[PBMW]

Sandvik should have a bar and a topper insert , I love those topper inserts , (bur free).

This...
Toper inserts are great.

 

[michiganbuck]

Taps are expensive but are so fast.. Often much of the tap area is little used or dulled
.. Might it be possible to save a quantity of dull taps and then send them out for cut-off and re-pointing.

custom taps? could they be made a little longer to accommodate cut off?

 

[dstryr]

Single point with a topper insert like mentioned above.
Get a carbide 3/8 bar.

 

[Mud]

The threads are .600 long. One nut is .600" long threaded full length, the other is 1" long with a counterbore.

 

[michiganbuck]

Another tapping suggestion is to figure tap life and pull them at about 70% of life and have the ends resharprened by a top grinding shop that can restore end geometry at half or less than the price of new. So you might get another 70% or better for lower cost. Taps beginning to end dull can start making a tight thread before they are shot.
And still another idea is to qualify the tap drill for size.. Often a under size drill can stress taps to shorter life. A tap drill at the top of you thread specification can extend tap life.

No I am not trying to talk you out of single pointing you should try that for time and cost.

 

[Mud]

The tap wear is not a big problem. Getting them made and having them cut the right size when delivered is a PITA though, and now would be a good time to make a switch. We really want to go to single pointing because tapping requires that we tap almost twice the length of the nut before it is cut off, which wastes bar length.

 

[Limy Sami]

How about ? - go here http://ecatalogue.korloy.com/korloyMain.html?lan=en and look for ILH13N-11

Which should be an internal, left hand inserted threading bar, with a minimum bore dia of 16mm & 32mm length of cut.

 

[rnmmhunter]

Turn a right hand internal thread bar upside down and run in reverse. Done

 

[Tony Quiring]

Or get longer tap and make multiples at once.

Tap once cut 4

 

[Conrad Hoffman]

I think that was called a nut tap, but I don't know if they're common anymore.

 

[jkruger]

Are you facing the back side in a second operation? If so why not tap them last?

 

[6061Mike]

Turn a right hand internal thread bar upside down and run in reverse. Done

Upside down is relevant to the machine tool I guess... I think (been a few years since I been on a lathe) in Mastercam (with a Haas lathe) you threaded a lefthand external thread by running Z- to the Z+ direction (again, this all depends on your machine)

 

[bigjon61]

L166.0KF-D06C-2C (3/8 threading bar) with a R166.0L-11UN01-160 insert. (16 TPI topping, 1/4" IC insert) for left handed applications. Change the R's to L's and vise versa to reverse configuration (normal).

 

[rnmmhunter]

I run left hand theads with a right hand bar all the time. From z positive to z minus

 

[6061Mike]

Turn a right hand internal thread bar upside down and run in reverse. Done

I run left hand theads with a right hand bar all the time. From z positive to z minus

Huh? So you flip the bar around (180 degrees, regardless of "upside down/right side up" ) to run right and left hand threads?

 

[bigjon61]

I run left hand theads with a right hand bar all the time. From z positive to z minus

And it is even easier on a CNC.

 

[rnmmhunter]

Blank the nuts out and thread them on a second op.