An observation and recommendation about IRO's hack 'n tap kit

[Nimrod]

I recently installed an IRO hack 'n tap yoke onto my NP242 TC. It was a straight-forward and fun little project. I haven't had a chance to test for vibrations yet because I've got to deal with a couple of unrelated issues before I can drive the Jeep. But I expect no problems.

I did make one observation about IRO's kit that I will pass on, along with a recommendation born of my experience for anyone considering this modification.

The installation instructions call for drilling a 1/4 inch pilot hole into the end of the output shaft (after cutting), followed by a 5/16 inch hole to be tapped. Drilling a pilot hole makes good sense of course, considering that the shaft is hardened steel. To ensure a straight and centered hole, IRO sells a drilling jig for $30, which I bought. Oddly though, the alignment hole in the jig is 5/16 of an inch, which makes it fairly useless for aligning the pilot hole. And once the pilot hole is drilled, the path of the 5/16 drill bit is determined and the jig becomes pointless. I overcame these issues and managed to get a perfectly centered and straight hole, but I will not credit iRO's jig with the success of the process.

My recommendation to anyone considering this modification is save $30 and do not buy the jig. It is not as helpful as it should be, in my opinion. With a little ingenuity you should be able to make a better jig yourself for a 1/4 inch pilot hole.

Here are some pictures to show off my handwork:

 

[Tim_MN]

Many Hack & Tap failures are caused by drilling off-center.

You could have used the jig, and a 5/16" drill to make drill bit start point. The start point does not need to be full diameter. Once the 5/16" drill makes a centered starting point big enough for a smaller drill bit, switch to the smaller bit.

 

[Nimrod]

Quite right. I agree completely. Ultimately, that's exactly what I did after I ground off about a half inch of additional shaft to get past the first hole that I started off-center with a quarter-inch bit.

I did not say that the IRO jig is entirely worthless. I said that it is not as useful as it could be, and that it is not worth buying in my opinion. To elaborate further, I would have found the jig much more useful if it were designed to snugly accommodate and align a 1/4 inch bit to aid in drilling the 1/4 inch pilot hole because once that hole is drilled, the jig's job is done. I hope someone finds this information helpful some day. And that's all I've got to say on the subject.

 

[Tim_MN]

For someone who is not experienced, the jig is useful, will probably help prevent failures, and I would recommend it.

I am a skilled Machinist, so I just winged it using my calibrated eyeball and a center punch.

 

[1990JEEPXJ]

Make a dot on the center of the shaft with a marker and spin the shaft. That will show if it is off center or not. Then center punch and carefully drill. That's how I did it and it worked great

 

[jjnavarro]

I'm about to buy one.
Does anyone have a jig they'd like to sell me?

 

[x-jay vision]

I have a jig. I could ship it on Monday.