keel bolts

[PabloPicasso]

The only difference is the impact driver has a1/4" hex socket and the wrench has a square section driver head 1/4, 3/8 or 1/2" and is able to deliver a greater torque, my impact driver ( just bought a new one as I gave feckless my previous one rather than let him borrow it) is capable of delivering up to 180Nm which I think is ample for most jobs the 610Nm of the Milwaukee is huge but I guess it comes in useful for breaking the initial bond but I wouldn't want to use it to tighten up much, too many grease monkeys and tyre fitters stretch bolts and studs by using them.

Yes, it was absolutly the right tool for breaking the bolts out. That's exactly what the impact driver was made for, and what a great job it did even though it took 5 or 6 minutes driving away before the bolt started to move.

I cannot imagine how difficult this would have been with a wrench extension, scaffold pole, and tapping with a hammer

 

[fisherman]

Yes, it was absolutly the right tool for breaking the bolts out. That's exactly what the impact driver was made for, and what a great job it did even though it took 5 or 6 minutes driving away before the bolt started to move.

I cannot imagine how difficult this would have been with a wrench extension, scaffold pole, and tapping with a hammer

Oh yes, and the long extension puts the socket out of kilter until the nut rounds.

 

[PabloPicasso]

Oh yes, and the long extension puts the socket out of kilter until the nut rounds.

I hope that's not the voice of experience speaking...

 

[Zing]

Yes, it was absolutly the right tool for breaking the bolts out. That's exactly what the impact driver was made for, and what a great job it did even though it took 5 or 6 minutes driving away before the bolt started to move.

I cannot imagine how difficult this would have been with a wrench extension, scaffold pole, and tapping with a hammer

Indeed. Take care with impact drivers. They are great at breaking bolts. A nice clean snap in the middle. 2 bust today!

 

[Fr J Hackett]

Indeed. Take care with impact drivers. They are great at breaking bolts. A nice clean snap in the middle. 2 bust today!

Tightening or undoing?

 

[Moodysailor]

Good points, and in a time honored tradition of contributing to thread drift ;-) - another comment on impact drivers. If you get one of the very high-torque ones, or if you use it a lot, get a set of impact sockets (yes they are a thing), and whatever you do - don't use 12-point sockets on normal hex bolts. 12-point sockets are useless for any hex fitting IMO, and will round off faster than anything if used with an impact gun.

I've had non-impact sockets crack open when using an impact gun, and one threw bits all over the place. I bought myself a set of impact sockets years ago - they still look good as new (and got regular use as I was an engineer at the time) and have a 100% success rate

 

[PabloPicasso]

Tightening or undoing?

Wow,? now that would have really been a problem. When I hear things like that I just thank God for the air I continue to breath and carry on

 

[PabloPicasso]

Good points, and in a time honored tradition of contributing to thread drift ;-) - another comment on impact drivers. If you get one of the very high-torque ones, or if you use it a lot, get a set of impact sockets (yes they are a thing), and whatever you do - don't use 12-point sockets on normal hex bolts. 12-point sockets are useless for any hex fitting IMO, and will round off faster than anything if used with an impact gun.

I've had non-impact sockets crack open when using an impact gun, and one threw bits all over the place. I bought myself a set of impact sockets years ago - they still look good as new (and got regular use as I was an engineer at the time) and have a 100% success rate

Yes, we used a special impact socket set for just this reason.

 

[davierobb]

An impact gun is the perfect tool for this job, however its worth remembering that all impact guns are not the same. We tried 2 new guns with no success, lots of noise but no action. Borrowed one from a friend who works on the railway and it popped the nuts in a few secs. £400 vs £150.

 

[PabloPicasso]

An impact gun is the perfect tool for this job, however its worth remembering that all impact guns are not the same. We tried 2 new guns with no success, lots of noise but no action. Borrowed one from a friend who works on the railway and it popped the nuts in a few secs. £400 vs £150.

Yes, a decent impact gun is expensive. That's why I recommended borrowing one! They cost a lot of beer tokens... Especially for a tool one might use only rarely. But I'm glad it all worked for you.

 

[Bilgediver]

Tightening or undoing?

I suspect more harm than good would be done if an impact driver was used to tighten the keel bolts as the required torque for keels attached to fibreglass hulls is a relatively low figure and there would be a danger of crushing the hull material below the nut and washer. I remember a Westerley Vulcan on the west coast of Scotland suffering from this fate with the nuts driven partly through the hull. This was some years ago and cost£5000 to get both keels sorted to the satisfaction of the surveyor.

 

[Fr J Hackett]

I suspect more harm than good would be done if an impact driver was used to tighten the keel bolts as the required torque for keels attached to fibreglass hulls is a relatively low figure and there would be a danger of crushing the hull material below the nut and washer. I remember a Westerley Vulcan on the west coast of Scotland suffering from this fate with the nuts driven partly through the hull. This was some years ago and cost£5000 to get both keels sorted to the satisfaction of the surveyor.

Which was why I asked Zing the question. re snapping two bolts.

 

[PabloPicasso]

What is the crush resistance of fibreglass. How would you even work that out?

 

[Poignard]

Indeed. Take care with impact drivers. They are great at breaking bolts. A nice clean snap in the middle. 2 bust today!

Were you tightening or loosening them?

 

[Fr J Hackett]

Were you tightening or loosening them?

Already asked that question he seems reluctant to answer though.

 

[Poignard]

Already asked that question he seems reluctant to answer though.

Perhaps he will answer me as I'm sure he likes me better than you.

 

[Bilgediver]

What is the crush resistance of fibreglass. How would you even work that out?

A fraction of the crush resistance of high tensile steel and the reason why using the wrong torque can destroy the integrity of the hull. I do it by feel . An impact driver set for steel work would damage the hull if used for tighteming bolts in a fibre glass boat.

The actual torque would depend on the boat.

 

[Motor_Sailor]

I suspect more harm than good would be done if an impact driver was used to tighten the keel bolts as the required torque for keels attached to fibreglass hulls is a relatively low figure and there would be a danger of crushing the hull material below the nut and washer. I remember a Westerley Vulcan on the west coast of Scotland suffering from this fate with the nuts driven partly through the hull. This was some years ago and cost£5000 to get both keels sorted to the satisfaction of the surveyor.

I'm afraid this is rather muddled.

Keel bolts have been traditionally sized using the cross sectional area and material strength of the bolt. The assumption is that the attachments to the keel and boat structure can take the full load. This load transfer therefore requires the nut to be torqued using a Nut Factor of .2 as in any regular bolted joint.

Ensuring the hull structure can handle the loading from the keel bolts is the function of the number of keel bolts specified plus the load spreading features such as backing plates / fabricated floors or even steel subframes. There's no point in specifying a 'ten ton bolt' if you're going to attach it a 'one ton structure'.

Any examples where a properly torqued nut 'pulls into the hull material' either shows an inadequately sized backing plate or shoddy build quality of the hull structure. It signals something is wrong. The solution is not to leave the keel bolts 'loose' as at some points they could be expected to develop their full design loads. That's why they're that size.

 

[Bilgediver]

I'm afraid this is rather muddled.

What the problem has been on some occasions is that people working on keel bolts have looked up the recommended torque for keel bolts in an engineers reference book The figures in these books are based on working with all steel connections. If you rent an impact driver you are likely to obtain values base on torquing up bolts securing steel assemblies. If you take these values and apply them to keel bolts which pass through a fibre glass hull then you could seriously damage the hull.

The boat builr=der will supply the correct torque for these bolts which will be a lower value than for the same bolts when used in steel assembly.

Just be carefull as it is too late when you have used the wrong figures and crushed the hull material in way of the keel bolts and nuts.

 

[dankilb]

If you rent an impact driver you are likely to obtain values base on torquing up bolts securing steel assemblies

Mechanically speaking, presumably you’d only use drivers (after threading on by hand, of course) to spin fasteners down. Still torque them the proper/manual way.

(Maybe different in construction/civil engineering to apply max torque.)

I thereby assumed the sheared bolt/stud queried above was due to it being seized upon disassembly, as you shouldn’t be impact torquing anything down anyway.