Screwed up drilling out a broken stud.

I bought a Jaguar IFS last week to put under my 57 F100. While stripping the crossmember, I snapped off a couple 3/8-24 studs that hold the spring plates to the lower control arm. One on each side. I drilled one of the studs out using a letter Q drill (.332") and was able to clean the threads up with a pick and a thread chaser. On the other arm, I wasn't so lucky. I drilled well into the threads, every bit of 25%. While looking down into the hole, the threads are gone from the 12 o'clock position to the 3 o'clock position.

Being that this is a suspension part and I probably don't want the spring plate shooting off while I'm driving, it looks like I'll be buying a used control arm at the pick n pull this weekend. However, is drilling oversized and tapping the next size up (25/64 drill, 7/16-20 tap OR letter Y drill, 7/16-28 tap) a safe option?

 

Yep or a Heli coil .

 

Sure you could go oversize but why not re drill and helicoil it? Least then your bolts/hardware will be the same size. And when done correctly helicoils are super strong.

 

Helicoil would be great. However, you will need to make sure you have the arm securely fixed and the drill bit needs to be fixed in position as well. As you know, the new larger bit will try to follow the original hole for a center otherwise. Anyone with a good drill press or better yet a bridgeport can help you out here.
But really, this is what you get trying to use Jaguar parts in a Ford truck!

 

Another item is called a Time-sert. It's basically a one piece barrel, kinda like a heli-coil but solid instead of a "spring like" design. Hard to explain on a tiny iPod thing, but TIMESERT.COM will show you what I mean. Good luck, I've used them with GREAT results, Ken

 

timeserts are cool, but spendy. helicoil or the like should work fine, i've used them on all kinds of stuff and if anything they seem like they're stronger than the original threads.

 

To get the drill centered, weld a nut over the hole and drill through the nut.

 

I could still screw that up! Seriously, that is a good tip.

 

Ditto helicoil

4TTRUK

 

"To get the drill centered, weld a nut over the hole and drill through the nut"

Agreed. Yes, you and I could still screw it up but... I am confidant that you are now paying close attention to the outcome.
Your question "is drilling oversized and tapping the next size up (25/64 drill, 7/16-20 tap OR letter Y drill, 7/16-28 tap) a safe option?".

Yes.

Dale
Cleveland OH

 

You have plenty of meat in the arm so I would go to the 7/16-20 and I would consider changing the other holes that are in a similar application so that they are common to each other.

.

 

Great tip!

 

Clean sert for a suspension piece. looks like a piece of pipe with threads on both sides. Not expensive and they will out perform a heli coil any day of the week.

 

"But really, this is what you get trying to use Jaguar parts in a Ford truck!"

Doesn't Ford own Jaguar?

 

EZ-Locks. Used them to repair holes in the shop

 

when i have broken bolts like this
and they are broken of near level
with the surface i put a washer
over the hole and weld the washer
to the broken bolt then weld a nut
to the washer that way the heat
from welding free the rusted bolt
no way to screw up the treads in the
hole or if there are plenty of space
around i drill a hole same size as the
broken bolt on some flatstock and
countersunk the hole then weld it to
the bolt and fill the countersunked hole
with weld let it cool for a minute then
unscrew it by twisting the flatstock

 

Grainger carries an ***ortment of thread repair inserts http://www.grainger.com/Grainger/wwg/search.shtml?op=search&N=11223&in_dim_search=1&sst=subset .

 

I'm just happy for you the stud is out and the thread repair can commence.

 

timeserts are soft. a steel, solid wall insert is the ticket. used in blocks when a head bolt hole is stripped.

 

I like the way you think.

 

while you're looking on the internet, look up keenserts. Just another way to skin a cat.

 

I write CNC programs at a machine shop here in town. I asked the tool room manager if I could have a heli-coil and if I could borrow a drill, the special tap, and the insert tool. Took all of five minutes.

 

Looks like a good fix.

 

Good job. That fix should last just fine and not cause any long term problems. Feels good to get it fixed right and doing it yourself.

 

Well done. Did you have a problem keeping hole straight?

 

No, I just went slow and let the drill follow the original hole.

 

Helicoil and red lock***e.

 

i don't know if the helicoil is as strong, but i do know you will not have to go thru the agrivation of finding out you have 2 different sized of hardware someday. i can't count how many times i have done this and wondered "why isn't this bolt threading in" when you brab the wrong one.

 

Helicoils work out great, but make sure you take to Machine shop, that has done this. I worked at Machine shop for over 6 years, before i went in to Service Station business. Good Luck.
Cruise On, Old Dude.

 

I just saw you did what I would have done. Cruise On, Old Dude.