Cutting bolts

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nathanlee

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It's been a long time since I've posted in the Practical Boat Owners forum, which correctly suggests that it's been far too long since I've undertaken any sort of practical boat ownership. However, I'm trying to get my act together, not least to relieve the boredom of these depressingly short days I have to suffer for the next 6 months or so.

Anyway, to avoid turning this in to a blog post, I'll get right to the point. I have a load of trough deck bolts that are far too long, and now I'm fitting the remainder of my insulation and headlining, they're becoming a problem. How do I cut them?

Most of them are in positions that make a hacksaw impossible (also very tedious) and while an angle grinder would make short work of them, it'll send sparks flying all over the place, probably my face in some of the more confined spots.

I can't afford to buy new bolts, and I'd rather not remove them all since they are currently watertight.

What's the best method of cutting them down in situ?

Cheers,

Nathan
 
I would use a Fein Multimaster, which doesn't throw dust everywhere, but if you don't have one how about a Dremel (with suitable cutting disc) and an assistant holding a vacuum cleaner nozzle nearby?
 
borrow an air gun and compressor either with a chisel or a hack saw. Whichever it is you will have to grind the remnants flat to avoid having your scalp lacerated fifteen times a day, though Sikalflex blobs can offer some protection.
 
If the bolts are good and tight and you have a reasonable amount of shank protruding through the nut...just nip the shank as close to the nut as possible with a grinderette and then wiggle the shank backward and forward a couple of times with mole-grips or a small adjustable spanner. If they are stainless they'll normally snap off easily. Have done this loads of times when fitting toe-rails and getting at the bolt shanks was too difficult.
 
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Dremel with the 90 degree gearbox adaptor ( £20 ) and the diamond cutting disk ( £12 )

Bloody expensive tool but it will cut through steel bolts and is small enough that if you can see it you can probably cut it.
 
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nathanlee said:
Ah, I had to google it, but I've got the Bosche version of that. I've just tried it, and it minced the blade and didn't really do much damage to the bolt. :(

Presumably I have the wrong blade on it?
Click to expand...

I have cut bolts with a Fein HSS blade but they are really only intended for sheet metal cutting [because the teeth have no set] so you have to help the tool by not letting it get too hot and not forcing it. I found it best to cut a vee into the bolt rather than forcing the blade into a narrow slot. If the teeth get worn you can move the blade round a few degrees to use an unworn part.

I think the Dremel would have been easier but I didn't have one then. I think you could probably buy a Dremel for not much more than the price of a Fein HSS blade.
 
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Dremel type tool

there are some dremel type cheapo tools out there that are less than 20£

THis one would do it 12.99£

http://www.amazon.co.uk/Am-Tech-60Pc-Mini-Drill-Grinder/dp/B0012XFGVC

very useful for all sorts on the boat !!!!!!!!!!!!!!!!!!

edit :I got mine from aldi 3 years ago same price but has variable speed and flexishaft used it for all sorts even cut some slate with it !

Double edit !!!!! Use eye googles !!!! the ordinary cutting disc are fragile and dangerouse to eyes !!
 
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No electricity required.
On bolts with about 20mm or more sticking out, and 8mm dia or less, simply use an adjustable spanner end on, tight on the threads, with the tip of the spanner just touching the nut. Bend the bolt about 30 degrees back and forth. On the 3rd go it should snap off just one thread below the nut. Should take 3 seconds per bolt.
This only works with stainless, which is much more brittle than steel.
Method shown to me by a boat builder over 20yrs ago....
 
Seanick said:
No electricity required.
On bolts with about 20mm or more sticking out, and 8mm dia or less, simply use an adjustable spanner end on, tight on the threads, with the tip of the spanner just touching the nut. Bend the bolt about 30 degrees back and forth. On the 3rd go it should snap off just one thread below the nut. Should take 3 seconds per bolt.
This only works with stainless, which is much more brittle than steel.
Method shown to me by a boat builder over 20yrs ago....
Click to expand...

That's a slick trick, Nick.

:D
 
Snapping off bolts with fatigue

This works well on SS as said. However it can put a lot of strain on the substrate that the bolt is in. For instance if the bolt were holding down wooden strips you might find the head will be pulled into the wood and so loosens the bolts. Only use this method when the bolt is into really tough material. ie for 4mm bolts it should be OK if bolt has a washer on f/g. But be careful olewill
 
Grind? Chop?

I have cut off quite a few 5/16" ss deck screws with a Dremel tool. The little disks do not last too long...
And as others have noted, keep a wet towel around the work area and wear really good safety glasses.

Plan B... might be to do what a large CN boat builder used to do. Judging by the sharp chisel shape of the bolt end right at the top of each nut, they used a (powered??) bolt cutter to several hundred per side after the deck was attached.

LB
 
You need one of these : http://www.homebase.co.uk/webapp/wc...s|14418763&c_1=1|category_root|Tools|16849334

Thats the 'toy' version of an excellent tool. Mine is still going strong after 7- 8 years occasional abuse. You can otherwise go to Screwfix and pay twice as much for a 'proper' one.

Forget the blades supplied with the cheap one, they are made of plastic and last about three seconds. Get decent metal cutting blades from Screwfix, with hardened offset teeth. Dont run it too fast - they have speed controls and I find mine works best at about 4/6ths speed.

Its a tool which I only use occasionally, but my 'electric knife' will go through almost anything, makes no sparks, and I wouldnt be without it, making short work of any cutting job - as long as I have decent quality blades in it. Basically if you can get a hacksaw to it, you can use this tool.
 
I would persevere with the hacksaw. Use a brand new good quality blade. Take it out of the frame if access is difficult. You can get handles which fit on to one end of the blade itself. I have one in my toolbox but I'm not sure where it came from to be honest. Otherwise just wrap loads of Gaffa tape around the blade for about 2 or 3 inches at one end to make a pad which is comfortable. Make sure that the blade will cut as it is pulled towards you. The blade will break otherwise. Put a bit of three in one oil or similiaron blade before you start cutting. Saw the bolts smoothly and gently taking care not to twist the blade. I would think that when you have sawn half way you will probably be able to snap the bolt using mole grips. Finish with a file.
 
Thanks for all the replies folks. Much appreciated.

I've solved the problem. I was in homebase this afternoon and they had a special offer on a Dremel; £39. A bit beyond my budget, but it's always worth buying decent tools, so I took the plunge.

It works a treat, even with the standard cutting discs that come with it. It slices through the m8 bolts like butter, although for the sake of fellow newbies that read this I should point out that it's essential to wear some goggles. The discs have a habit of exploding and sending vision impairing shards all over the place. I wouldn't have mentioned it, but I've lost count of the number of engineers and metal workers I know that will happily slice away with an angle grinder with no eye protection.

Thanks again,

Nathan
 
Depending on the diameter of the bolts you don't need to cut them at all. Just clamp a mole grip on the end of the thread and bend back and forwards a couple of times and they shear off at the nut head. You will still be able to undo them afterwards if you need.
It may be a bodge, but it works up to about 6mm.
 
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