[AT] Drill size for bolt tap question

Stephen Offiler soffiler at gmail.com
Thu Apr 13 14:23:58 PDT 2017


Good old JB Weld should do the trick.  The regular, 24-hour cure stuff has
about double the tensile strength of the 5-minute JB Weld.

SO


On Thu, Apr 13, 2017 at 3:53 PM, Al Jones <farmallsupera1 at gmail.com> wrote:

> What would be a recommendation on the epoxy?
>
> Al
>
> On Thu, Apr 13, 2017 at 3:05 PM, Stephen Offiler <soffiler at gmail.com>
> wrote:
> > 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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