[AT] Drill size for bolt tap question

[Stephen Offiler]

Yup.  My chart actually says the 7/8" tap drill on a 1"-8 thread gives
73%.  You'll have substantially less engaged thread if the tap drill hole
is already 15/16", down in the 30% range I'd estimate.  I would fill that
gap with a good epoxy rather than Loctite.

SO


On Thu, Apr 13, 2017 at 2:45 PM, <rlgoss at twc.com> wrote:

> If I remember correctly, those drill/tap size recommendations are so you
> retain 75% overlap in the thread engagement.  It should work, but will be a
> loose fit during assembly.  It will easily be stipped out again, so use
> caution.
>
> Larry
>
> ---- Al Jones <farmallsupera1 at gmail.com> wrote:
> > I've got some wallered out holes on a Farmall Super A torque tube that I
> > want to fix.  They need to be 5/8" coarse thread, but somebody stripped
> 'em
> > out, then did some sort of funky drilling, and now my holes are 15/16" in
> > diameter.  I'd like to fix it myself but the longer I look at it the
> more I
> > fear a machine shop visit is in order.
> >
> > My notion is to try to tap the holes for a threaded insert.  If I drill
> the
> > holes out any larger for a larger tap, it's going to eat away the square
> > boss on the side of the torque tube, so I want to avoid that. Now, the
> > chart I am looking at says you need a 7/8" hole for a 1" tap. That means
> > the existing holes are 1/16" too big.  Can I still tap it with the 1"
> tap,
> > Loctite the daylights out of the insert, and get it to hold? These holes
> > are on the left side, and there weren't many implements that used these
> > holes, plus it's going to be mainly a show/plow day tractor.  But I do
> want
> > them functional and they have to "look good."
> >
> > I have a good torque tube, but this is an early (probably built the first
> > or second day of 1950 production) white demonstrator tractor, so I'm
> trying
> > to keep the castings original.
> >
> > thanks!
> > Al
>
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