View Full Version : un threading tap

01-11-2010, 07:31 PM
:confused: Hi, being new on here I would like some help about a Tap to thread. I have borrowed one for now but need to find a new one I can keep. It is a 1.25-20UN GH4 4FP, 5.75 inches long. I found one at Traverse company but they do not list it as UN. Do I need to worry about this? I have searched around but have not found any others listed. Also if I find one could a person drill and tap the end? It is a special tool from Ford. They want $700. dollars for the kit. Thanks

01-11-2010, 08:03 PM
"UN" is the thread form or profile.

"Ford" or anyone else is quite free to make or specify any thread form, pitch or nominal (outside) diameter that they wish to suit their purpose as a "special".

At a guess, I'd say that that the "GH4 4FP" is a Ford code.

The limited availability and cost and suggest of a special tool/use rather suggests that it is a "Ford" job/tool/use specific item.

If the job is a "one-off", why not ask a local Ford Dealer or Mechanic as I'd be surprised if someone hadn't found a "work-around"? They might even do the job for you for a fee which may save you the effort of looking for the tap as well as the cost.

If the tap is HSS, I don't fancy your chances of tapping the end of it.

It may be possible to make the tap "from scratch" in your own shop to your requirements.

If its a "must have" "Ford" item I can't help any further.

doctor demo
01-11-2010, 08:20 PM
I'm afraid that I'm not going to be any more help than Tiffie, but depending on what size hole You need threaded in the end it could be possible to have a hole put in the end with an EDM and then silver solder in an appropriate sized threaded bushing. That won't be cheap either though.

I am curious as to the specific application of this tap and why it needs to be threaded .


01-11-2010, 08:56 PM
the only thing the tap does is makes threads in the injector sleeves and then you use it pull the sleeves out. The one from Ford Rotunda has the end drilled and taped and you use it as a gear pully, the threads and tap are what hold it to pull out.

01-11-2010, 09:19 PM
Based on what you've said, it sounds as though it should be possible to come up with a much cheaper way to pull the sleeves. It may be cheaper, for Ford counting labor costs, to have a special tool that avoids having to unscrew the tap and screw in something else to pull with...but I doubt you're worried about that.
And it sounds as though the thread spec isn't too critical; a standard tap ought to work. You'll need to come up with a threaded plug to be the puller after you tap the holes, but if you've got a machine shop that should be pretty easy.

01-11-2010, 10:14 PM
If that is all it is, it would be an hour or so to make a tap/puller from drill rod and thread the end prior to hardening. You could probably even use low carbon steel and Kasenit case harden it.

01-11-2010, 10:53 PM
Buy a 1.25x20 tap and drill and tap the end with the square and you have the same thing you borrowed. Or you can weld a nut on the end and use it to run the tap in the sleeve and then screw a slide hammer in the nut and pull the sleeve.

I have used a tap to pull stuff like that several times. I used a tap to pull the roll pin out of the body of the Cummins PT fuel pump to replace the governer sleeve. Of course the tap didn't last long but it did the job.

01-13-2010, 11:56 AM
I would use a standard tap to thread the sleeves, and a separate tool to thread into the sleeve for pulling. That would eliminate the chance of breaking the tap teeth in the sleeve if you had a stubborn one.

01-13-2010, 12:36 PM
.................................................. .................

It is a 1.25-20UN GH4 4FP, 5.75 inches long.


Where did you find this info?

The "GH4" indicates a ground tap (most all taps are ground these days as opposed to cut), the "H4" part means .002" over nominal (each H represents .0005").

As a guess, the "4FP" could mean four flute, plug style.

So far doesn't sound like anything but a normal tap, except maybe the length which I don't know about.

01-13-2010, 12:58 PM
Quote from JJwelder, "It is a special tool from Ford. They want $700. dollars for the kit. Thanks."

It's a Ford factory repair tool. I sure would like to supply them to Ford as well as other special tools they sell that are easy to make.