Fix crossthreaded, threads?

[peejay75]

Alrighty, gang, got another one.

This is also not life-or-limb, but it's nagging me and I'd like to fix it properly, if within my scope!

Got a crossthreaded bolt, and it will only go in sideways. I'm guessing a tap is out at this stage, correct?

Is a heli-coil or some sort of thread insert gonna be the next-best thing? And if so, any tips on getting everything straight? My last/only attempt with a heli-coil was about 30 years ago on an engine block and it didn't go well (hand drilling, no kind of alightment setup, etc) and still haunts me to this day!

 

[no704]

Get a new screw, possibly a set screw. Run it thru the hole from the backside.

 

[whateg01]

Chasing the threads and then carefully starting the bolt would probably be fine for that cover. Can't tell if you can do it, but if it was me, I would probably chase the threads with a tap, from the back side of you can, where the threads might still be good. Then cut a chunk of all thread to use as a stud. Loctite that in and use a nut. If it was doing more than holding a cover on, yeah I would use a helicoil.

 

[MadMechMaster]

I would drill out and tap for the next size up.

 

[Bert_]

It's just holding the tin. Self taper?

 

[lilredex]

If it tightens up crooked, leave it be. If not run in a tap from the back or make a guide to keep it straight from the front, an angled block clamped to the side of that lug will do.

 

[peejay75]

If it tightens up crooked, leave it be. If not run in a tap from the back or make a guide to keep it straight from the front, an angled block clamped to the side of that lug will do.

A tap from the back won't wipe out the front threads, will it? By design it should "realign" the bad threads on the front side?

 

[peejay75]

It's just holding the tin. Self taper?

Didn't know about that, thanks!

 

[peejay75]

Y'all are all right, as long as the back threads hold, that's what matters, right?

Now, while we're here, do they make heli-coils/thread repair for through holes, i.e., what if the helicoil is longer than the hole?

 

[The Cobbler]

as said try to tap it from the backside , or drill & tap to a larger size,

 

[PCustoms]

as said try to tap it from the backside

 

[whateg01]

A tap from the back won't wipe out the front threads, will it? By design it should "realign" the bad threads on the front side?

The threads should be the same from one end to the other. What it will do is "wipe out" the newly formed threads from the cross threading.

Helicoils come in different lengths.

 

[peejay75]

There's one in every group, no?

 

[ArcIndWeld]

Not a big helicoil fan myself Keenserts are where it's at but overkill in this application. Far easier to just drill out and tap to the next size up since it looks like the hole in the sheet metal is already plenty large.

 

[RoninB4]

-Running a tap in will not re-align the threads, it will likely render all of the existing threads useless. Even if it just secures sheet metal the vibration from a motorcycle can loosen a fastener when the threads are bunged/re-cut, even when a thread locking agent (Loctite) is used. Going the next size up, in inch or metric, is probably a better solution. Having body tin waving in the breeze while at speed is distracting and seldom ends well.

 

[dchawk81]

try to tap it from the backside

Keep it lubed and don't go too fast.

 

[PCustoms]

There's one in every group, no?

Keep it lubed and don't go too fast.

Apparently two...

 

[dchawk81]

Apparently two...

At least.

 

[DGersic]

If you’re going to try to fix it, go to autozone and borrow the thread repair kit. Being pedantic about it, a tap cuts new threads, and you don’t have enough meat left there to be cutting new threads. A thread restore looks like a tap, but isn’t supposed to cut, just moosh the threads back to where they are supposed to be.

With what’s there, I’d probably just drill and tap it to the next size up, Assuming you can find or get an acceptable bolt, that’ll work fine.

On a similar problem here (700R4 transmission inspection cover where somebody tried to use wood screws to replace the correct fasteners), I did drill and helicoil the holes. Bit awkward to do laying under the car and looking up, but it worked fine and four new screws hold the cover in place now.

 

[peejay75]

Keep it lubed and don't go too fast.

What the heck...

That's what [pronoun of choice] said?

 

[peejay75]

A thread restore looks like a tap, but isn’t supposed to cut, just moosh the threads back to where they are supposed to be.

THAT'S the response I would expect Google's AI (which I've been pleased with, so far) to tell me! The threads are there, they just need mooshing back...Now, would you agree there's no harm in trying the tap first? Then I'll know?

My preferred approach would be: 1) try the tap and lube, er, cutting oil, from the back; 2) if that doesn't work, now try the thread repair kit or 2b) heli-coil...would prefer to keep the fastener the original size

(That first heli-coil attempt I talked about was trying to fix a boogered up hold in an engine block bellhousing mating surface...the hole ended up crooked AND elongated...the heli-coil went in, but everytime I had to remove the bolt, the heli-coil would come out with it! If memory serves me correct, my first GJ post was probably "how to plug hole in cast iron and retap"...i think all responses said "impossible" or "not worth it", haven't returned to that project because [see other projects] still haven't [yet] seriously tried to progress with welding/brazing...sorry that got so long-winded!)

 

[peejay75]

-Running a tap in will not re-align the threads, it will likely render all of the existing threads useless.

Oops, saw that after I posted, Ronin! That's what I was afraid of (rightly so?). Progress!

 

[Jacko264]

You could drill a hole from the back just smaller then a 6mm nut and pull the nut into the aluminium cast with a bolt
only drill the hole the thickness of the nut

 

[whateg01]

You could drill a hole from the back just smaller then a 6mm nut and pull the nut into the aluminium cast with a bolt
only drill the hole the thickness of the nut

Seems like a good way for somebody with little experience in such things to crack the mounting tab and not be able to use it at all anymore

 

[Junkdrawer Dog]

A short piece of rusty wire twisted with a fifty year old pair of pliers.

 

[peejay75]

Seems like a good way for somebody with little experience in such things to crack the mounting tab and not be able to use it at all anymore

Funny, the donor engine had a bolt broken off in a similar location, heat and hammering on the extractor cracked the mounting tab!

 

[peejay75]

You could drill a hole from the back just smaller then a 6mm nut and pull the nut into the aluminium cast with a bolt
only drill the hole the thickness of the nut

That's clever, and I'm fairly confident that I would completely ruin the part, this time.

 

[peejay75]

Thread restorer/chaser has been ordered. Doubt I'll be able to get it from the back  but I will try to use an alignment jig from the front.

 

[DGersic]

THAT'S the response I would expect Google's AI (which I've been pleased with, so far) to tell me! The threads are there, they just need mooshing back...Now, would you agree there's no harm in trying the tap first? Then I'll know?

My preferred approach would be: 1) try the tap and lube, er, cutting oil, from the back; 2) if that doesn't work, now try the thread repair kit or 2b) heli-coil...would prefer to keep the fastener the original size

(That first heli-coil attempt I talked about was trying to fix a boogered up hold in an engine block bellhousing mating surface...the hole ended up crooked AND elongated...the heli-coil went in, but everytime I had to remove the bolt, the heli-coil would come out with it! If memory serves me correct, my first GJ post was probably "how to plug hole in cast iron and retap"...i think all responses said "impossible" or "not worth it", haven't returned to that project because [see other projects] still haven't [yet] seriously tried to progress with welding/brazing...sorry that got so long-winded!)

Thread restore first. A tap removes metal. You don’t want to remove it if at all possible.

 

[jsaw]

Like someone mentioned earlier, I have cleaned up threads by taking a bolt the same size as the threads You are trying to fix. File, or grind grooves into the threads and run it in from the back side.

 

[Jacko264]

I’ve been giving this some thought .
How about drilling the hole out then countersunk both sides .
then use JB Liquid Metal to fill the hole and countersunk.
next drill and tap to fit the bolt
G

 

[yhprum]

Years ago I bought some thread restorer from locktite. It was a two part mix, some granular stuff mixed with the epoxy. So I mixed it up, and stuffed in them buggered up hole. Put the screws in lightly torqued. Had quite a bit left over, it never hardened, wtf. A few weeks later I happened to unscrew the screws. The mixture had hardened! And the screws held torgue. So that might be an option for you.

 

[Jacko264]

How about get a 6mm rivnut and drill the hole to fit the rivnut , the rivnut type you need has grips on the sides but fit it on the back side , no need to use a tool to nip the rivnut
as long as you drill the Hole the correct size
G
ps you could put thread lock on the out side of the rivnut to help it hold

 

[Kasal]

Why not use a longer screw (drilling out the threads) and a self-locking nut on the other side? It would be a quick and straightforward solution.

 

[whateg01]

Gonna be a little hard to get the nut on and off with it being under the cover, don't ya think?

 

[peejay75]

Sorry I missed all these responses, but thank you! (Had to finish the "filling holes in wood" project, so now I can jump back on this one).

I have cleaned up threads by taking a bolt the same size as the threads You are trying to fix. File, or grind grooves into the threads and run it in from the back side.

I like this idea, if I can get some all thread and file flats in it, or something so I can turn it from the back side.
(Edit: or a set screw!)

How about drilling the hole out then countersunk both sides .
then use JB Liquid Metal to fill the hole and countersunk.
next drill and tap to fit the bolt

Another good option, provided I could get the hole centered and drilled...but I have another scenario where this Liquid Metal could come in handy, needed something like that years ago, and never finished researching it...may get some and practice on scrap...

thread restorer from locktite

will look into that as a possibility!

How about get a 6mm rivnut and drill the hole to fit the rivnut

I like that, too, if the rivnut flange isn't too big for the mounting ear

 

[Jacko264]

I think the metal filler was called bellzona. It was two paste that you mixed
if you get it wear plastic gloves
I seem to remember it was designed for the US navy
G

 

[Milton Shaw]

Time for you to get a set of thread restore files. Each one has 8 different pitches on it. Three of them cover just about every thread pitch out there. Two for SAE and one for metric. You start where thread are good and the work toward the bad threads. A lathe to spin the bolt backwards makes it easier. Each thread file was $10 each when I bought mine but that's too many presidents ago for that to be even in the ball park.

 

[KwikFab]

 

[whateg01]

I

Time for you to get a set of thread restore files. Each one has 8 different pitches on it. Three of them cover just about every thread pitch out there. Two for SAE and one for metric. You start where thread are good and the work toward the bad threads. A lathe to spin the bolt backwards makes it easier. Each thread file was $10 each when I bought mine but that's too many presidents ago for that to be even in the ball park.

Can't wait to see op trying to use those on internal threads!