Big nuts...

[Jonathan Webb]

Well big as far as I'm concerned.

I need to undo some 38mm stainless nuts on stainless studs, which may be torqued up pretty tight as they hold the keels on and have a bit of flex to deal with. They also have the same sized nuts to lock as well, nut against nut. I will later need to put them back & tighten to 150ft.lb

I have been advised to go for 3/4" drive stuff, but have also had suggested an air impact wrench. The T bar presumably has the potential to deliver more torque - if I can arrange it satisfactorily, whereas the air tool would deliver less torque but more cleverly

Before I buy anything I wondered: Which delivers better or more reliable undoing power - a T bar setup in a bit of a confined workspace (as shown. The other side only has access from above, through A3 sized hatches), or a cheapie air wrench (either 1/2" or 3/4")? Or other suggestions?

Thoughts appreciated.
Many thanks

 

[Gragson]

Access does not look great?
I would blow torch then decent breaker bar which looks like it would need a short 3/4 extension to L down onto the nut, an impact socket on the end probably would not be a bad idea

 

[Dcal]

Is it M38 stud bar or 38 across the flats?

 

[hotponyshoes]

Crowfoot, extension and a breaker bar?

 

[frank horton]

watch out for stainless......I never ever use anything but hand tools to tighten or loosen ST/ST......it gauls the threads......
St/ST can be quite soft, generally it is NOT high tensile........
decent hex socket and a 3/4 breaker bar is the way to go......
those cheapish Chinese 3/4 socket set are really not that bad......I have two......

 

[ibrooks]

Forget a cheap impact of any variety, it'll just be a waste of money.

A decent length T or breaker bar will allow you to deliver more torque IF you've got the room to swing it and get it in there in the first place and that can often be a big IF.

A decent impact gun of some variety should rattle them off quite happily.

Stainless is a bu@@er for galling if the nut and bolt are the same grade so be careful and clean and oil the exposed threads before you try to take them off. Hopefully the person who fitted them used appropriate grades to avoid the problem but there's nothing more annoying then getting a nut loose only for it to go tight again for no apparent reason and you end up having to cut or snap the thing.

 

[Gragson]

those cheapish Chinese 3/4 socket set are really not that bad......I have two......

Although that cheese sandwich might be stronger

 

[Jonathan Webb]

Access does not look great?
I would blow torch then decent breaker bar which looks like it would need a short 3/4 extension to L down onto the nut, an impact socket on the end probably would not be a bad idea

I need to be wary of heat as it goes through and is bedded on fibreglass and I really don't want to impair the structural integrity. I haven't tried anything yet as I've only just determined the nut size.

 

[Jonathan Webb]

Although that cheese sandwich might be stronger

Vintage cheddar with ketchup. Comfort food rooted in childhood. I couldn't crop it out

 

[8ob]

I need to be wary of heat as it goes through and is bedded on fibreglass and I really don't want to impair the structural integrity. I haven't tried anything yet as I've only just determined the nut size.

That will typically be a 60mm spanner size, are you sure its an m38 stud?

Bob

 

[Jonathan Webb]

Is it M38 stud bar or 38 across the flats?

M38 across flats

 

[Jonathan Webb]

That will typically be a 60mm spanner size, are you sure its an m38 stud?

Bob

? The nuts are 38mm across the flats. Not 60mm, that is seriously big. I measured them all, 2 measurements at least on each nut, plus info from the internet as to likely sizes. I apologise if my wording is not engineering correct though.

 

[Jonathan Webb]

Crowfoot, extension and a breaker bar?

Crowfoot? Not a term im familiar with.

 

[Jonathan Webb]

Forget a cheap impact of any variety, it'll just be a waste of money.

A decent length T or breaker bar will allow you to deliver more torque IF you've got the room to swing it and get it in there in the first place and that can often be a big IF.

A decent impact gun of some variety should rattle them off quite happily.

Stainless is a bu@@er for galling if the nut and bolt are the same grade so be careful and clean and oil the exposed threads before you try to take them off. Hopefully the person who fitted them used appropriate grades to avoid the problem but there's nothing more annoying then getting a nut loose only for it to go tight again for no apparent reason and you end up having to cut or snap the thing.

It's a quality boat, from 1974, and reasonably well built so I'd expect the fasteners to be up to spec.
Thanks for the tips about going gently WRT galling and about cleaning and oiling. Any kind of oil?

 

[ronan]

Crowfoot? Not a term im familiar with.

 

[8ob]

It's a quality boat, from 1974, and reasonably well built so I'd expect the fasteners to be up to spec.
Thanks for the tips about going gently WRT galling and about cleaning and oiling. Any kind of oil?

Its probably an inch and a half AF spanner size then and not metric.

Bob

 

[Gragson]

I'd syringe them them with diesel, thin enough to get through and leave for a day, favorite releasing goo list go on forever.
They might crack off dry but you should get a "feel" if thats going to happen.
Take the point on no heat due to FG and agree with other not to use a rattle gun as first option

 

[Gragson]

Not sure I would use a crow foot, I would want as much direct action as poss with a full hex socket

 

[wyn]

As Bob says, i'm sure there are no metric bolts that use 38mm spanners.

38.2mm is 1-1/2 inches and probably a 1"unf thread.

 

[Jonathan Webb]

Its probably an inch and a half AF spanner size then and not metric.

Bob

The table I saw put 1 1/2AF at 38.1, which is probably well within my measurement error. I asked (clearly on the wrong forum) if my measurements suggested an imperial size but got no joy. On a 6 point socket, is that 0.1mm critical? As I haven't bought anything yet, it may not matter unless that size is rare.