Removing a broken machine screw

[DTR]

Good afternoon all,

I've already posted this on the Myford Yahoo group, but I expect this is just as good a place to ask.

Yesterday I discovered the bottom half of my ML4's clasp nut sitting on the drip
tray. I found that the retaining screw / pin had sheared off below the level of
the hole. Please see the photos linked below. In case there's any confusion,
this is the screw that interacts with the automatic traverse engagement lever.

Can anyone suggest a way of removing the broken part of the screw?

Thanks

edit: I'm having a blonde moment, I can't remember how to embed the photos

 

[Dangermouse]

Is it thick enough to dril a small hole is and use extractors, as per link.

http://www.ebay.co.uk/itm/8-Piece-3-50m ... 3a6e48449d

You can get all sorts of sizes and i have used them with great sucess.

 

[DTR]

Thanks for the tip. The screw is 3/16" so the smallest extractor you've linked should do it.

Let's try that embedding thing again...

 

[davem62]

hi if it's not seized in,you could try the screw removers, that fit in the cordless drills and bite into the screws or bolts without having to drill them out, just centre punch to give them a start.trend do them
good luck dave

 

[jimi43]

Mmmm...there's something else going on there Dave.

That pitting original?

I think you might find that the screw is seized in there mate.

Try the methods above but be prepared to drill out and re-tap or even having to put an insert in there and re-drill and tap.

Jim

 

[DTR]

Mmmm...there's something else going on there Dave.

That pitting original?

I thought that too, screws don't just shear when they feel like it. As far as I am aware, the pitting is not new. Maybe original casting that's below the level of the machined face? I'll have a look at the other half of the clasp nut to compare.

Try the methods above but be prepared to drill out and re-tap or even having to put an insert in there and re-drill and tap.

Drilling out and re-tapping wouldn't be the end of the world, if that's what it takes.

Thanks for the replies so far

 

[jasonB]

As its steel in non ferrous metal you can disolve it out with Alum.

J

 

[Hutzul]

I've done a few of these broken bolts over the years, in factory maintenance and also motorcycles etc. Easiest way I've found is to centre punch the offending stub and to drill it out with a drill bit that is smaller than the tapping drill size, taking care to move your drill as needed to centralise the hole you are drilling.
Once you have a hole through try a bigger drill bit and if you can see the thread on one side try to remove bits with a scribe, or try to tap it out.

It helps if you can soak the bolt overnight or for an hour or two.

Good luck.

 

[Wildman]

build a coffer dam around it and fill with vineger. Leave for 48 hours to disolve the rust it shoule then tap out fairly easy or come out with an easyout

 

[t8hants]

Drill a small hole in the stud and if you don't have a stud extractor use the tang end of a very small file, knock it into th hole. Also heat the part up with a hot air gun the brass/bronze will expand far more than the steel stud and should let go, if not get it good and hot and quench it in water. that should break the friction with thermal shock.

 

[Lons]

Locallised heat, small gas pencil torch comes in useful, often is enough to loosen the bond.

I usually drill and try a screw extractor then if that doesn't work I do what hutzul says and drill out with a size just shy of the bolt / stud excluding the thread. As long as you keep it straight, it leaves almost nothing behind and doesn't damage the threads. At worst (and has happened to me only once) the hole has to be opened out and tapped to the next size stud to hand. Straightforward if the tools are available and for occasional use you don't need to spend a lot.

Never thought of disolving the metal or the rust - interesting

Bob

 

[dickm]

Good afternoon all,

I've already posted this on the Myford Yahoo group, but I expect this is just as good a place to ask.

Aha. Didn't recognise the name when I read that posting on Yahoo half an hour ago !

 

[Phil Pascoe]

Go through the routines to free it up, get a Dremel with a cutting disc and cut a small slot in the steel. Use a small screwdriver and if you're lucky, it'll work. It won't take long, and won't do too much damage to the surrounding metal. I've done it successfully before, but soak it in plus gas, diesel or something first - you only get one go at it.

 

[No skills]

Carefull with the extractors you can use in a cordless, my makita sms is currently (has been for a long time) out of action due to a snapped bolt. I drilled it and wound the extractor in.... snap! yep broken bolt now has broken extractor in the end of it :evil: :evil: :evil:

And to top it off, since its been in storage something really heavy fell on it and smashed the trigger assembly...

So best of luck with your.. err.. extraction..

 

[Jamesc]

One tip I have seen but never used is to weld a new stud on the end of the broken screw. This has two benifits, the localised heat should help to loosen things and the stud gives you somthing to get hold of. I think it would be very difficult in your case as the screw is so small but may be useful on larger sized studs,

James

 

[Phil Pascoe]

If you can get to the end of the screw, fine - but all you'd end up with here is a pool of molten metal.

 

[Sheffield Tony]

yep broken bolt now has broken extractor in the end of it :evil: :evil: :evil:

This has happend consistently whenever I have tried to use stud extractors, leaving a nice little hardened insert in the stud to prevent further drilling. It seems rather predictable to me - the stud wouldn't come out with enough torque to shear it, so the (rather thinner) stud extractor surely needs to be of really special stuff to stand a chance.

 

[jimi43]

I have an old set of screw extractors I came across at a bootfair and I have an oriental set I bought ages ago.

They are like chalk and cheese. The old set is far better steel...I know it is hardened but it is also tempered correctly and I never have a problem with these. Before I got this set...well...let's just say the oriental set now only has the big ones!! :mrgreen:

Jim

 

[Keith 66]

I have never had any luck whatsoever with extractors, most times i get to do this job its on a boat engine or outboard motor, the latter are fitted exclusively with soft lead alloy bolts that shear off very easily corroded into the aluminium. Trick is to centre punch accurately then go up the drill sizes until you can pick out the bits with a scribe. Once you have a start for the tap you are away. Heat is good as well. As for welding it needs a good tig welder to carefully build up the screw until a nut can be welded on the top, Often used by gunsmiths to remove sheared screws.

 

[Eric The Viking]

Worst case, is there someone doing spark erosion near you?

It's not cheap, but it really does work well. I had a bolt removed from the Beemer's exhaust (R80RT), as some numptie (not me!) had put a mild steel bolt into a stainless silencer - the bolt fair exploded with rust. It was about £50 but the new can was £180. The thread was usable afterwards and didn't need any special cleanup (I might have run a tap down it - can't remember).

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