removing broken bolt in oven...


Fancy self cleaning oven - went to set it to clean mode this morning and whilst removing the shelf supports one of the bolts has broken off :-(
It was tight (they always are) but not massively so :-(
So, as I now can't fit any shelves in the over, I need to get the broken bit out somehow. Ideas? Access isn't fantastic and I don't seem to be able to get to the back of the screw (there is masses of insulation that appears to be impossible to remove.
Another possible option would be just to "glue" it back somehow - any glue that might do. I'm not sure drilling it out will work but I'll give it a go when it's cooled down (currently it's at 450 deg C :-))
Bugger. And I'm meant to have a day off to fix the fence not the oven :-/
Darren
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On 19 May, 12:56, dmc@puffin. (D.M.Chapman) wrote:

couple of thoughts.... might be easier to drill/move when still "hot"?
is it snapped flush or any chance of some molegrips being your friend on a stubby bit?
or those reverse screw extractors...mixed reviews ISTR but may do the trick here?
cheers JimK
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Will try warm later.

It's worse than that - snapped down in a hole. It's a 6mm bolt, snapped in a 5 mm recess. No chance of getting anything on the end of it :-(

Yeah. Might be the only option I suspect. Grrrrr.
Cheers,
Darren
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D.M.Chapman wrote:

Do you need to remove it? Can you not drill another hole nearby and fit a self tapping screw instead?
Bob
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Not easily - it needs to line up with a shaped part of the shelf bracket that hooks over the screw. It's the only bit that actually touches the side so it wouldn't be trivial to fit something elsewhere.
Last resort will be to try to make up some sort of bracket to hang down with a thread on the end. Dads got a set of reverse drills and some easyout thingers - I'll give that a go first.
Nothing to lose (he says tempting fate ;-))
Darren
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wrote:

If it's down a 5mm hole, y not drill it right out with a 5mm drill and tap the whole thing back to 6mm, for a standard bolt or set screw? No DIY kit is complete without a basic set of taps and dies, and a set of srew extractors: once you have them a whole new world of repair opportunities arrises. The latter are hard and break easily so unless the broken bolt is fairly loose it is generally easier to drill out the softer bolt and retap. In extremis you can put a 6mm thread inside a drilled out 8mm bolt, tap this into the broken bolt's hole and then saw it off flush to take a new 6mm bolt.
S
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Right, that was the plan. All was going well until the bloody captive nut thinger started to spin. Grrrrr.
Anyway, long story short and all that, I now have a 9.5mm hole in the thin steel side of the oven. Ideally, I want a captive nut thinger (what are they called?) to put in but I've no idea how this would work. I'm imagining something that I poke through the 9.5mm hole and somehow swell it on the back so it becomes captive. Does this exist? If so, what is it called (and where the hell can I buy one or two and not 1000!)
Clinch nut comes to mind - is that the thing? A quick google suggests they need access to both sides of the panel which is rather non trivial (and potentially destroy the insulation that appears bonded on :-()
Maybe something like a giant (but short!) self tapping 10mm thinger with a 6mm thread in the middle - that would be perfect. Does it exist?

Yep, had all that, and some nifty backward drills that *almost* did the job. Then the nut started spinning and it all went pearshaped from then on :)
Still, most of the fence fixed. just the awkward panel to fit. Now to explain to SWMBO why we can't use the oven tonight...
Darren
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On Wed, 19 May 2010 17:43:28 +0000 (UTC), D.M.Chapman wrote:

I'm sure I've seen some square nuts with a thin spring steel piece fixed over them. They push into a square hole from the side that you can get to and clip themselves in. Unfortunately I can't think of a name for them or where to get them, but maybe someone else can?
SteveW
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They're used in equipment racks. Not sure if you're thinking of cage nuts or spring nuts.
Cage nuts go into the square holes in the risers in a rack. That way when you're trying to mount the (heavy) equipment in the rack the nut is in position and all you've got to do is push the bolt through the flange on the kit, through the square hole and into the nut, which can't rotate. Easier then to do it up.
Spring nuts slide into slots in the rack (and so their position can be adjusted) but again, once in the slot they can't rotate and so it's easier for the poor bugger using them.
These klods:
http://www.knuerr.co.uk /
provide them for their equipment racks although I don't know if they're suitable for what you need.
--
Tim

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Hmmm.... cage nuts. That's an idea. I could square off the hole with my dremel and I've hundreds of cage nuts at work - we use stacks of them. Dunno why I didn't think of that.
Dunno how important it is that the oven is sealed though - I can imagine steam filling the insulation via the hole which seems less than ideal. Also, would they cope with 500 deg C? (I guess I could just never clean it again :-))
Still, it's an idea...
Cheers,
Darren
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On Wed, 19 May 2010 19:35:12 +0000 (UTC), dmc@puffin. (D.M.Chapman) wrote:

Cage nut needs to be fitted from the other side to which you have no access. Rivet nuts (especially for a hole now nearly 10mm) usually need horribly expensive setting tools. A better solution might be to make the hole bigger so a captive nut can go through and then mount the captive nut (eg http://cpc.farnell.com/jsp/level5/module.jsp?moduleId=cpc/437698.xml ) on its own small steel plate. Pop rivet the steel plate (backed with fire gum) into the oven wall.
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Peter Parry wrote:

Peter, I assume that this nut is forced into the steel plate so that the serrations keep it from rotating. If this is the case, I would try and peen the edge of the serration end, so that the heat/cold cycles don't loosen it over time. If it does loosen, the next time the bolt is removed, the nut might fall out into the void.
Dave
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wrote:

You are correct - the insertion method is to press the fitting into the metal sheet. Once inserted the end is expanded by putting the flat end on a steel plate, putting the ball end of a ball pein hammer into the serrated end and whacking the flat end of the ball pein with another hammer to turn over and expand the insert.
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On Wed, 19 May 2010 19:38:53 +0100, Tim Streater wrote:

Again, if Darren wants one I can give him one or two.
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Steve Walker wrote:

Cage nuts.
http://www.canford.co.uk/Products/20744/16-025
http://www.canford.co.uk/Products/20630/55-681_CAGE-NUT-INSERTION-TOOL
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On Wed, 19 May 2010 20:05:28 +0100, Dave Osborne wrote:

Not sure they'll work, but Darren can find plenty of them at work!
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wrote:

That has rather made things difficult. There are numerous different designs of cavity wall fixing but whether you will find a heat resistant one that will fit in the gap and open up properly I don't know.
One further thought is that you might find that the sealer they use for exhaust pipes (Firegum?) can be used to fill the hole. Then when it is beginning to 'go off', set the bolt with its nut already on in roughly the right position, level off with more firegum, and hold it in place with something until it sets. Then run the oven up to temp to cure it before trying any load. It might work...
In similar vein, you might be able to glue a thicker piece of ready tapped plate (or a washer with your own new 'captive nut' glued to the back) over the top of the old hole (one of the push out blanks from a pattress box might be about the right size.).
S
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wrote:

Just checked, and firegum swells when it is heated, so you could set it in place with a little blowlamp flame so as to avoid the water condensation when you turn on the oven
A further, 'non glue', method, might be to make an oblong of strip steel as wide as the hole but longer. Tap this in the middle. Put a nut on the bolt, followed by a washer bigger than the hole, followed by the tapped piece of steel. Manoeuvre the tapped oblong into the hole then tighten the washer down on to it with the nut, neatly covering hole and giving you a new bolt ready mounted.
S
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Ok, that might work. I'd prefer it to be fairly air tight (so not keen on the cage nut idea) as I don't really know what's behind the panel.

Not entirely sure I follow this...
What keeps it in attached to the side of the oven?
One thing I was pondering was a strip of steel with a couple of selftappers one above, one below the hole. Then a bolt sticking out of the strip and I can then hold the shelf bracket to that with a nut+washer. Will need to check it'll still allow be to take out the shelf bracket though. Is that what you meant?
Darren
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wrote:

You are clamping the sides of the oven between the tapped oblong - which you have poked, on the end of the bolt, through the 9.5mm hole - and the conventional washer, by tightening the lock nut down while you hold the hex end of the bolt at the desired position. (Its a pretty standard method to use lock nuts like this - as anyone tensioning cam chains on bikes will tell you.)

Similar idea, but in my case the strip of metal is between the two skins of the oven rather than on top of the inner one, and, with a lock nut you don't need the self tappers... But you will have to make sure the nut still leaves you room for whatever the shelf attachments are, just as you would with the self tapper heads.
As for steam, I should think that firegum would fill any gaps for you whichever way you proceed. S
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