Drill and tap vs combination drill & tap for m8 fastener

[JHZR2]

Two of the belly pan bolts on my ML320 thread into a steel structural crossmember. The threads for the M6 bolts are loose. The structural item is maybe 1/4” thick steel, I’d guess. MB usually uses speed nuts, or has square holes with a press in metal female speed nut, but not these.

I’d like to drill and tap to M8, then use a threaded insert with loctite red to give me the M6 threads.

The question is what tool? It’s not a high consequence or very exact tolerance application. I just don’t want the fasteners to come out on a big bump.

So is a separate drill and tap really best, or can these combo units, when done with a slow hand drilll and a lot of oil, do good enough?

 

[D60]

Those are for sheetmetal only. I personally wouldn't try in greater than 14ga

 

[RooflessVW]

I would pop some rivnuts in.

https://www.rivetsonline.com/39316-kit-50-assorted-steel-metric-ribbed-l-series-rivet-nu/kit-39316

 

[Trav]

I just tap m6 bolts out to m7 and use m7 bolts (home depot, amazon bolt depot, etc) They look almost the same only it takes an 11mm socket not a 10. No oversize drilling required just run an m6 drill through and use the m7 tap. Not for every m6 bolt use but for many things like underbody panels it works a treat.

https://www.amazon.com/Irwin-Indust...qid=1757371869&sprefix=7mm+tap,aps,163&sr=8-3

 

[JHZR2]

I would pop some rivnuts in.

https://www.rivetsonline.com/39316-kit-50-assorted-steel-metric-ribbed-l-series-rivet-nu/kit-39316

That’s what should have been used in there imo.

 

[JHZR2]

Those are for sheetmetal only. I personally wouldn't try in greater than 14ga

Thanks. So this is good for reference regardless. So if doing any more substantial thickness, you HAVE to use a standard tap then?

What good are threads in sheetmetal? I can’t see how they’d have any holding power at all.

 

[Astro14]

I would pop some rivnuts in.

https://www.rivetsonline.com/39316-kit-50-assorted-steel-metric-ribbed-l-series-rivet-nu/kit-39316

Yep - Rivet nuts would be perfect for this. Drill them out, use an M6 rivet nut, and keep the same fasteners.

 

[JimPghPA]

If you can't find anything you need for that job, try McMaster-Carr online.