HeliCoil Help

[jeffgrice]

Greetings.

I have a threaded hole on my alum transmission where the slave cylinder mounts that is stripped. So I have been researching helicoil.

I can access the hole with about 3-4 inches of working room (without removing the trans) before I hit a frame rail.

I have read conflicting reports on if I must drill first or if I an start with tap. I know ideally to drill.

BUT...

I do not have the clearance to get a drill in the hole.

Any wisdom is much appreciated.

Thank you.

Jeff

 

[rlitman]

This is what angle drills and stubby bits are made for.

 

[dnschmidt]

You're asking a question that you already know the answer to. It ain't happening.

 

[manwithtools]

Greetings.

I have a threaded hole on my alum transmission where the slave cylinder mounts that is stripped. So I have been researching helicoil.

I can access the hole with about 3-4 inches of working room (without removing the trans) before I hit a frame rail.

I have read conflicting reports on if I must drill first or if I an start with tap. I know ideally to drill.

BUT...

I do not have the clearance to get a drill in the hole.

Any wisdom is much appreciated.

Thank you.

Jeff

It does need drilled to the proper hole size before using the Helicoil tap. Instead of removing the transmission, can you simply lower it enough to gain access? What kind of car is this?

 

[jeffgrice]

It does need drilled to the proper hole size before using the Helicoil tap. Instead of removing the transmission, can you simply lower it enough to gain access? What kind of car is this?

It is a Superformance Daytona Cobra

 

[manwithtools]

It is a Superformance Daytona Cobra

So rear wheel drive, nice car BTW. Can you remove the crossmember that supports the rear of the transmission (if it has that type of arrangement) and support the trans with floor jack and let it drop low enough to access the hole with a conventional drill?

 

[mreisner]

Can you get a short reamer in there? Stubby drill bit and an angle drill would probably be your best bet, but if you don't have access to that a short reamer would probably do it as you could turn it with a wrench, it should cut aluminum easily.

 

[Wamsutta]

That hole looks like it has plenty of meat around it for a Keensert. That's what I would rather use in that instance. Way more durable than a Helicoil.

 

[Rusted Nut]

How about just tapping with a size up from what you have now. Get one size up bolt. Aluminum is pretty easy to tap.

 

[Wamsutta]

How about just tapping with a size up from what you have now. Get one size up bolt. Aluminum is pretty easy to tap.

You can do that, but you'll end up with the same soft aluminum threads that you started with.

 

[2oolhound]

What scares me is the stripped out hole looks like it must intersect the hole from the stud (you can see sticking out to the right). For bolts that size I'd be worried about the corner of the aluminum breaking off.

An alternative would be to lay a 3/16" piece of steel along the top of the flat area covering both holes (the one at the top of the photo also). If you drilled a hole at the top of it where that other threaded hole is and then welded a stud sticking up where the stripped thread is you could leave the bad hole alone. You would need to bend a tab 90' up and drill it (for the bolt at the bottom of the photo) and a 2nd tab bent 90' down where you could attach this plate to the stud that sticks out to right of the stripped hole.

The slave may not allow to fit a 3/16" plate there though, just a thought as an alternative but a welder and bending skills required.

 

[WildBill]

Maybe use a rivet nut one size smaller so it fits in the hole without drilling.

 

[Wrench97]

What size is the bolt now?

 

[vssjim]

On holes like that where all the threads are gone in aluminum or magnesium I just tap them with out drilling when you can't get a drill in and with a new sharp tap and lube they cut threads fine and put in the helicoil and move on.

 

[mikey03]

Is it possible to drill into a soft metal like aluminum by hand in a small tight space by putting a small drill bit into a small tap holder or something like that? I did try once recently not because it was tight but because I happened to have a tap handle nearby and needed to drill one small hole in sheet metal and my drill was 20 minutes away

the tap handle didn’t bite down around the drill bit so it didn’t work but maybe if it was a hex bit base drill bit or something other than a tap handle that’s like that though

 

[decableguy2000]

Is it possible to drill into a soft metal like aluminum by hand in a small tight space by putting a small drill bit into a small tap holder or something like that? I did try once recently not because it was tight but because I happened to have a tap handle nearby and needed to drill one small hole in sheet metal and my drill was 20 minutes away

the tap handle didn’t bite down around the drill bit so it didn’t work but maybe if it was a hex bit base drill bit or something other than a tap handle that’s like that though

Yes it is. When I use Time serts in magnesium, I use the drill bit in a tap handle. M5-M8 size screws.

 

[Kurt4440]

Greetings.

I have a threaded hole on my alum transmission where the slave cylinder mounts that is stripped. So I have been researching helicoil.

I can access the hole with about 3-4 inches of working room (without removing the trans) before I hit a frame rail.

I have read conflicting reports on if I must drill first or if I an start with tap. I know ideally to drill.

BUT...

I do not have the clearance to get a drill in the hole.

Any wisdom is much appreciated.

Thank you.

Jeff

This was used on a piece of test equipment that was on loan to one of the facilities I managed. The equipment was expensive, but, more importantly, the equipment was needed at another plant ASAP.
For a low torque situation, it worked well.

That being said, I would pull the gearbox.

 

[2ndGearRubber]

If you have the confidence to attempt - the fix here is a stubby bit, air ratchet, and an adapter chuck for a 1/4 drive. 3 inches, and 4 inches, is a pretty big difference. 4" this seems possible, I'd at least get the tools out and start seeing what fits. 3 is another story. "Air ratchet drill chuck" in google shows you what I'm talking about, there's a variety of heights. I don't think you're getting a regular angle drill shorter than the ratchet/adapter setup. Promaxx is the slimmest version I see just taking a peek, mine are about that height. The flat-head air ratchet from SP air, the 1/4 is probably 3/4" thick, will get in there. Email Promaxx, they can probably give you the total height of that ratchet and chuck, you can work backwards from there. Maybe cut the bit down, depends on installed protrusion, and you still need to drill to depth. You can cut the bit short, drill until it can't go further, then leave the whole thing up in the hole and re-adjust the amount of bit sticking out. After that you will probably have to cut the tap in half, and cut the installer tool in half, and use something like locking needle nose vise grips to drive them carefully. Threaded bit angle drills exist, but I don't normally see bits above maybe 1/4. I'm guessing these are ~M8 threads? You can potentially do that repair, in that space. But if you have an issue, you now may have a bigger problem than when you started.

If that lower hole is stripped, my gut says the upper is not excellent. The "correct" move here is to remove the trans, and repair. However if you want to gamble some wasted money on tools, and the possible damage from a bad helicoil attempt, you have a lot to gain. If it were me, 4" I'd probably try. 3" I don't think is realistic. Also be aware that slave cylinder has a lot of torque on those bolts, it's fighting the pressure plate.

If this was a POS, I would consider an 1/8 diameter 90 degree die grinder, and a mirror. Clean out the loose thread as best you can, then try to run the tab straight into the case. You could also turn the bit by hand (just to remove what's left of the threads) but this is a massive PITA, slow, and gives an inconsistant hole size. Being it's a nice car, I'd recommend doing a good job.

 

[2ndGearRubber]

Just a thought, removing a motor mount and dipping the engine down on one side may fix part of your clearance issue. I'd consider pulling both mounts, sitting it on blocks of wood on the subframe, if it avoided a trans pull.

 

[joecon]

I would see if I could cut down a drill bit and see if I could turn it by hand to enlarge the hole. Then I would not use a keen Sert or a time Sert depending on the thickness of the casting. I would run the tap in by holding the end of the tap stedy and turning it with a wrench that fit the threaded part.

 

[ChevyEFI]

Looks like a Tremec 6 speed.

Pretty simple to unbolt and lower many RWD crossmembers to have a straight shot. If you have the access, and the exhaust disconnected, maybe you can lower and clear the rail.

 

[RoninB4]

I've only used a Heli-Coil insert when I was forced to, never been a big fan of that type of insert. The Heli-Coil inserts tend to back out when the component application requires removal afterward. I've used the install tool, a turret mill, and followed the mfg. instructions about breaking off/setting the broken tang into the material. Install goes just fine. When the fastener had to be removed (stamping die maintenance) the Heli-Coil often came out with the fastener. I've installed many of them and it was always like this. If there's not enough meat surrounding the hole for a different type of insert then you either have to use one, upsize the fastener, or weld and re-tap.

I really prefer the Keensert type because of the locking pins, which resist unwinding back out of the hole. They don't work well for through holes where there's pressure/vacuum or liquids (although they can sometimes be sealed), The application the OP shows looks like it's a blind hole with enough meat around it, perfect for a Keenert.

I would also advise that since the hole has been stripped out once that excess torque has been used or that the holding bolt was started wrong and cross threaded. Excessive torque calls for using Loctite (blue only) to simply hold the component on and not using gorilla-torque to keep it there. Cross threading calls for being more careful and using your fingers to get the bolt started with 3-4 turns to ensure it correctly started. Seen too many cross threaded holes from using pneumatic/cordless drivers without insuring the fastener is aligned and started correctly. It may look cool to just zip all the fasteners in but it's a habit of carelessness. JMO

 

[decableguy2000]

What size bolt is suppose to be used there?

 

[rust in the eye]

How about just tapping with a size up from what you have now. Get one size up bolt. Aluminum is pretty easy to tap.

^^
This has bailed me out a bunch of times. Depending of the size of the stripped hole I've sometimes gotten away with simply running the next size tap without any drilling. Don't forget that you'll find close dimensions in imperial vs metric. For example a 1/4-20 has saved me from a whole bunch of knackered M6 threaded holes.

 

[joecon]

You can Loctite the insert to keep it from backing out.

 

[chris142]

Can you put a longer bolt in the hole and catch the lower threads?