Subframe bolt install ssue 1

[Brittany Farley]

I am a supplier representative. I have front subframes that are having issues. We have nuts in the subframe with nycote. The bolt being installed is started by hand and they operator uses a tool to turn the bolt 3 times before sending it to the machine to finish bolting down. Sometimes it will fail and cause the operator to either reshoot it the bolt or to re tap the nut. The supplier insist they're thread checkers are checking the nuts and no issues on their end. The operator doesn't think it's a cross thread issue. Other theories are that the nycote is to thick in the nut. Do you all have any other suggestions?

 

[MintJulep]

@Brittany

As Tugboateng is correctly pointing out, there are several factors interacting that might all contribute to the problem.

It shouldn't be your problem alone to solve.

Somewhere up the supply chain there is likey a "production methods" group with the responsibility to figure things like this out.

 

[3DDave]

One thing that is really great is Nylok has no application data on their website that one would typically expect, but do list at least 16 OEM internal specifications, and who knows what they say, but that assumes these were coated in accordance with any spec.

"The supplier insist they're thread checkers are checking the nuts" ... before or after coating? And what are they being checked for / what checks are they doing and did they tell you their results or just give a generic "thumbs up" to indicate they don't know?

Same with the bolts.

 

[TugboatEng]

You will be alone in your problem because very few engineers work with E-Coat products in mass production level conditions. However, we all have small amounts of knowledge about coatings, clearances, assembly practices that together can help you solve you assembly problems. We love images but in your case I suggest you cover the part numbers on the item as it may be useful to your competitors or lawyers.

3DDave, they likely hired a family member to make the website. They already have the contracts. They clearly supply all OEM's doing E-Coat. What is their website supposed to do, encourage other customers to adopt E-Coat because their product can mask a hole for less? I would counter with gelled calcium sulfonate, no masking required but that has mixed popularity.

 

[3DDave]

Nylok is unlikely to have a "family member" doing their website.

The suggestion that few engineers work with all of this may include the ones who did this job or maybe some line worker decided the process was not enough.

 

[TugboatEng]

Maybe I should have stated that Nylock is an OEM supplier and specializes is large production so they don't really need smart website. A dumbed down website is sufficient.

 

[MintJulep]

Anyways, plenty of phone numbers to call. Ask to speak to an application specialist.

https://nylok.com/contact-us/

 

[BrianPetersen]

Captured nuts or weld-nuts in a welded component like this which is subsequently e-coated, is really common in the automotive industry, seen it myself about a million times. I can see that the internal threads in your nuts are not covered in e-coat, so that doesn't seem to be the problem.

If you haven't done so already, you need to grab some of those bolts and go down to the line yourself and check how easily the bolts thread into those nuts. Check fitment before welding, after welding but before e-coat, and after e-coat. If the nuts are tough to go on the bolts to begin with, you need to go upstream to the supplier and find out what's going on. If the bolts thread in easily before weld but are tough afterward, then something's happening in weld. Distortion, weld spatter, misalignment, whatever. If the bolts thread in easily with your fingers but the assembly process or tooling is having trouble, then that's the problem. Misalignment, insufficient or excessive clamping force, etc.

I'm sure you've already done this. Tell us your findings.

Hitting the bolt with a hammer to try to get the threads to start, isn't doing you any favours.

Someone already touched on this, but please confirm that you are starting both bolts by a few turns before tightening either one of them down, so that the part being installed has a bit of wiggle room for the bolts to align themselves. Also confirm that the part being assembled isn't trying to preload the bolts with a side load in any way. I can pretty easily see how that sway-bar bushing holder could be out of tolerance if the stamping process is off, or if the bushing is tight inside the bracket, leading to its natural hole-to-hole dimension not matching what's welded into the subframe. We like having one of the holes being a smidge oval in order to accommodate misalignment in that direction.

 

[enginesrus]

How thick are the captured nuts? Have they been checked with a thread gauge before the nyloc is applied?

A bolt with a starting taper and similar to self threading type bolt maybe the answer. I would want the nut to be thick enough and strong enough in case some of those need to be reworked.

Using a hammer to start a bolt is asking for problems, they should be hand started.

Why not just use a medium strength loctite?