Is there any reason not to replace a stud with a bolt?

[Fanum]

I'm still waiting on an exhaust stud to come from Motorworks, but I've got a nice new helicoil kit sitting here waiting to put it in when it arrives.

Is there actually any reason to use a stud rather than just sticking in a decent quality SS M8 bolt of the right length?

I've never really understood the use of studs rather than bolts......it seems unnecessarily complicated

 

[JayC]

Is there actually any reason to use a stud rather than just sticking in a decent quality SS M8 bolt of the right length?

Yes.

 

[thornley]

Yes.

+1

 

[Welshman]

Yes.

Definitely, you want to use a bolt, put a proper insert in

 

[Fanum]

Yes.

+1

Why then?

 

[duckspeed]

Can't think of any reason not to use a bolt instead of a stud, as long as a good quality high tensile bolt is used.
I think studs are used to speed up production, and for no other reason

 

[thornley]

Why then?

A very good reason.

Heads are alloy, how many times would you want to screw a bolt in and out of it. Much better to remove a steel nut from a steel stud and have the stud locked in place. Studs also act as a locator by having a plain area at the flange thickness and speed up production and fitment.

 

[Fanum]

Can't think of any reason not to use a bolt instead of a stud, as long as a good quality high tensile bolt is used.
I think studs are used to speed up production, and for no other reason

TY, that's what I was thinking.

Studs are easy enough to use, but I can't really see the need for mucking around with a pair of locked up nuts on the outside end to tighten it into place.....as long as a bolt is the right sort, it would seem a lot easier to just stick one in as a direct replacement........the fact that I'd end up with a bolt head rather than a polished SS cap nut is trivial and of no matter to me whatsoever

I was just wondering why they use them though........most other fixings are bog standard bolts rather than studs.....

 

[Fanum]

A very good reason.

Heads are alloy, how many times would you want to screw a bolt in and out of it.

Exhaust studs are hardly high use items........this will be the first time in 8 years that it's been undone.

 

[MikeO]

A very good reason.

Heads are alloy, how many times would you want to screw a bolt in and out of it. Much better to remove a steel nut from a steel stud and have the stud locked in place.

Yup - that sums it up...

Besides, can you imagine trying to fit headers single handed, if you didn't have studs to hang them off?

Mike

 

[Timpo]

A bit vague you are here Fanum.....

So, let me try and think an answer for you.


If the fixing hole is in alloy, using a helicoil insert effectively increases the strength of the hole's threads up to the next size (metric) for example, an M8 hole fitted with a helicoil insert has the integrity of an M10 fine taped hole...... and the engineers on here will appreciate that I am making this in a close to layman's terms as possible, so a bit of approximation is used.

Also, the stud is used so that the thread to fixing thread that can be disturbed often is between the nut and stud, and not the bolt and alloy (with or without insert). Constant undoing and tightening of a thread in alloy will soon see it strip out.

Another tip, if you ever need a metric fine tap, you can use the tap in the 'size under' helicoil kit. Eg, M10 helicoil tap is M12x1.5.
Fuel banjo bolts are a typical example of this if making fuel/oil tanks and connection, etc.

 

[thornley]

Exhaust studs are hardly high use items........this will be the first time in 8 years that it's been undone.

Some people change the exhausts far more often. No reason why you can't use a bolt but its far easier to use a nut splitter on a nut than try to remove a seized bolt and probably strip the alloy head. Also easier to locate the exhaust flange.

You could also cross thread a bolt in the alloy. Cross a nut and its easier to sort out.

 

[Timolgra]

Push comes to shove you could cut the head off the bolt...hey presto, a stud

 

[JayC]

Why then?

Studs are used so you don't pull the threads in the aluminum.
On studs you are tightening against the steel threads not the aluminum threads the bolts will go into.

 

[Timolgra]

Ah but, some large manifolds have a mix of studs and bolts

 

[Fanum]

Fairy nuff

I have to wait until the parcel from Motorworks arrives anyway, as the two ring gaskets and the bigger oval gasket have got to be replaced at the same time.

The 'fitting one handed' aspect doesn't come into play in this case...the stud on the other side is still there and still tight and in good condition (I did order two studs though just in case)


I like understanding things though, so it was worth asking

EDIT.......while I have some proper minds focussed on this.......I'm going top break the cardinal rule and ask 'what oil'

Seriously.....cutting oil as recommended for use when cutting the thread to insert the helicoil insert into......special stuff? Any old lubricant? any good substitute suggestions?

Sorry

 

[Timpo]

Also, stainless steel fixing is A2 or A4 (general availability) have poor properties when exposed to fluctuating temperatures (from cold to hot to cold to hot, etc) and also vibration. Increased vibration severly shortens the life of the SS fixtures in the A2 A4 grades mentioned.
Engineering studs used on motorcycles are not SS. The factories fit steel.

 

[duckspeed]

Ah but, some large manifolds have a mix of studs and bolts

True dat !!

 

[thornley]

Ah but, some large manifolds have a mix of studs and bolts

Quite right and the studs are used to locate. Some manifolds use dowels and bolts. All good engineering

 

[thornley]

Also, stainless steel fixing is A2 or A4 (general availability) have poor properties when exposed to fluctuating temperatures (from cold to hot to cold to hot, etc) and also vibration. Increased vibration severly shortens the life of the SS fixtures in the A2 A4 grades mentioned.
Engineering studs used on motorcycles are not SS. The factories fit steel.

Absolutely stainless is not a good idea on exhaust ports subject to very high temperature fluctuation. A2/A4 is not suitable. Exhaust studs are specified engineering components. Alloyed steel.