Cutting a 1/2" x 32 thread

[Pete22]

Had an occasion come up where I needed to cut a 1/2" x 32 internal thread in a lock ring. Didn't have an internal boring bar that small so I used a standard 10-32 tap. Mounted the tap in the tool holder and fed in using standard single point threading technique. What should I call it, MUTIPLE POINT THREADING ?
Result came out quite nice.

I'm sure others have done this before, curious to here your results.


Pete

 

[atex57]

Now that is slick!

Ed.

 

[Larry Dickman]

I would call it Mickey Mouse threading.

 

[jumpinjimmy447]

I wouldn't call it mickey mouse , I call it ingenious , and I don't think I would have thought of doing it like that , but now its another trick in my bag. I like it .

 

[yardbird]

Good Job! Wondering how did you do the pull out at the end? Did you stop the spindle at the end using a indicator at a very slow RPM?

Single point gives you a little fudge room at the end, using a tap seems the stop would have to be pretty much dead nuts every time or you'd bugger up the whole thing? Your lathe have a retract feature of some kine?

Brent

 

[Cole2534]

Had an occasion come up where I needed to cut a 1/2" x 32 internal thread in a lock ring. Didn't have an internal boring bar that small so I used a standard 10-32 tap. Mounted the tap in the tool holder and fed in using standard single point threading technique. What should I call it, MUTIPLE POINT THREADING ?
Result came out quite nice.

I'm sure others have done this before, curious to here your results.


Pete

Did the taper of the tap permit you to do it all in a single pass?

 

[Dan from Oakland]

Gonna file that one away for a rainy day!!! thanks!! Did sorta the same thing with a tap for another job- took a 3 flute tap, ground two of the flutes off and narrowed up the remaining one and used it for a thread mill for a bastard size ID thread. Narrowing the remaining flute minimized the rubbing from the tap lead. worked ok for a few holes.

 

[dsergison]

I've done this too. I Just wind the cross slide in quickly right before stopping. One hand on each control. Pretty easy. At 32tpi you could turn the chuck by hand. You certainly can turn the tap by hand and do it in one shot and it's the same amount of cut but the taps do deflect not being self supported in a hole so I do make multiple passes.

 

[CarlBoyd]

Did the taper of the tap permit you to do it all in a single pass?

Now that would be really slick!

CarlBoyd

 

[Ox]

I'm sure others have done this before, curious to hear your results.

I have 1/2-32 taps around her somewhere...

Otherwise I would have ground a point onto an old #5 center drill.



--------------------

Think Snow Eh!
Ox

 

[Pete22]

Thanks for all your comments.

In reply: I did it in 2 passes because I was afraid of breaking the tap. All of the cutting occurs on the taper of the tap. I had a thru hole which made it easier; just cranked in the cross slide at the appropriate time. This was all made easier because I did it on the worlds best threading lathe; a 1915 tiebar HENDEY


Pete

 

[EPAIII]

I would call it "job well done". Time for a well deserved break.

 

[L Vanice]

Keep in mind that the lead angle changes with diameter while keeping the pitch constant. A 10-32 thread lead angle at the pitch diameter is about 3.44 degrees and a 1/2-32 thread lead angle is about 1.19 degrees.

That means the 10-32 tap will not match the desired 1/2-32 thread profile because the trailing flanks of the tap threads will rub on the threads being cut. I am not saying the results are unusable, but the resulting thread form is likely a bit off from the theoretical profile.

Larry

 

[Pete22]

Larry:

Point well taken. The next question is how much is the interference ? Doing a super quick approximation I came up with 0.0026"

Pete

 

[Gordon Heaton]

. . .trailing flanks of the tap threads will rub on the threads being cut. . .

With a 10-32 tap in a #21 hole you have full circumference engagement. Sticking the same tap down a hole sized for 1/2" threads would result in a much lesser engagement, and I wonder if the trailing edge rub would be an issue. In any case one could grind back the tap for the desired clearance.

 

[DMF_TomB]

i once made a 1/4-127 tap by using the front of Vee tool bit to push or form threads. cut no chips. it was a very fine thread (max threads per inch lathe could do) and just used some anti seez compound for lubricant.
.
just remember you push or form threads the diameter changes. its like knurling you are pushing the metal and forming threads

 

[tnmgcarbide]

i have made improvised thread mills from taps by grinding off all but one flute, and then removing all but 2 or 3
teeth , and then grinding those to a point by removing most of the flank material. works well , but painfully slow.

 

[tomjelly]

How about this for easy pipe threading? No need to set a taper angle as its built in to the cutter, easy setup using a single cutter from a Ridgid die head. Be quick with the feed release though...

 

[Pete22]

Tom

Good suggestion. One limitation that immediately comes to mind is that my Hendey won't do 11 1/2 TPI which covers 1"-2" pipe

Pete