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

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:

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.

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.

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.

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

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

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