Exhaust stud sizing question

[JHZR2]

This is related to my 1991 MB 300D exhaust manifold question, but it’s more basic so I’m asking separately.

1) If finding studs is a challenge, is it best to just cut down a longer stud and chamfer the first threads?

2) Also are studs with a wider midsection preferable since they engage the host material better?

Situation:

I need Turbo manifold studs - stainless 27mm ool; 8mm & 11mm threaded

And Engine to exhaust manifold studs - black steel 43mm ool; 14mm threaded each side.

Both are M8x1.25

Notice the bulges in the center parts, and the fact that the shorter one has irregular length in one side vs the other.

Belmetric has lots of options but none with the thread lengths what I require. Should I get some that are close and cut them down?

Other places may have other options but they all seem to be necked down in the middle. Not sure if that matters.

I’d need to cut down 14 studs which may be easy or not. I have an angle grinder fwiw, but am mainly concerned with damaging threads including to vice it down.

Any recommendations?

 

[Hall]

Other places may have other options but they all seem to be necked down in the middle. Not sure if that matters.

I presume you mean thinner. If so, absolutely don't use those. This center section is where the bulk of the anti-shearing strength comes from.

Notice the bulges in the center parts, and the fact that the shorter one has irregular length in one side vs the other.

This is by design. The critical part is the end that threads into what 'part' you're dealing with. Make sure you match that (or exceed it). The hole and tap depth in the 'part' will obviously factor in so you can't always go too long either, plus you don't want much, if any, exposed thread before the shank section. In my previous work, our engineering standards said thread depth had to be (at a minimum) 1-1/2 times the thread diameter.

but am mainly concerned with damaging threads including to vice it down.

Run a thread die on them no matter what, even if they look okay.

 

[D60]

Double nut the end you want to hold.

Extra Man Points if you buy a 5C collet block and 8mm collet

Also, a machine shop will chuck them up in a collet with backstop and get them all whatever length your heart desires...probably within +/- .002" and can easily chamfer the freshly cut threads. Probably take 15 minutes to do 14 of them

 

[slacktide_bitog]

McMaster has M8 studs 14mm on one side, 8mm on the other side, 28mm OAL

 

[JHZR2]

McMaster has M8 studs 14mm on one side, 8mm on the other side, 28mm OAL

That was an option I saw, and can cut down the 14mm end.

Double nut the end you want to hold.

Extra Man Points if you buy a 5C collet block and 8mm collet

Also, a machine shop will chuck them up in a collet with backstop and get them all whatever length your heart desires...probably within +/- .002" and can easily chamfer the freshly cut threads. Probably take 15 minutes to do 14 of them

More things to buy, yay!!! Not entirely sure what I’m supposed to do with this? I assume I’d use a threaded stop to hold the dead end at a certain length and then cut the stud to what I want?

I presume you mean thinner. If so, absolutely don't use those. This center section is where the bulk of the anti-shearing strength comes from.

This is by design. The critical part is the end that threads into what 'part' you're dealing with. Make sure you match that (or exceed it). The hole and tap depth in the 'part' will obviously factor in so you can't always go too long either, plus you don't want much, if any, exposed thread before the shank section. In my previous work, our engineering standards said thread depth had to be (at a minimum) 1-1/2 times the thread diameter.

Run a thread die on them no matter what, even if they look okay.

Thank you for the guidance!