[AT] Drill size for bolt tap question

[charlie hill]

Al there is a product called Belzona (sp) that should work well.
It can actually be drilled and tapped
but generally it's only available to licensed applicators.
Or at least I think that is the way it used to be.

However, have you looked into Helicoils?  I'm not sure what sizes they
are available in but you might get lucky.

Is the rail you are going into steel or cast iron?  If it's steel you can 
always
look at welding it up and re-drilling and tapping it to the proper size.
Just make sure you find a PRO welder to do the job.

Charlie

-----Original Message----- 
From: Al Jones
Sent: Thursday, April 13, 2017 3:53 PM
To: Antique tractor email discussion group
Subject: Re: [AT] Drill size for bolt tap question

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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