Removal of tiny roll pin

HI all, Am trying to dissassemble a mechanism where the inner part of the assembly appears to be held in place with a small roll-pin in a blind
hole in an alloy casting. The pin is only about 1mm dia - I can't drift it out as its in a blind hole. I cannot remove the mechanism to the workshop as its in a vehicle. Any bright ideas on how to get it out?
In desperation, i did try drilling it, but of course they are tempered spring steel so just ended up with a blunt drill. I haven't got any carbide bits or similar small enough.
Mike
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MikeH_QB wrote:

That is such a sick construcktion that I doubt it really is that way.

Bright? How about a (hardened) screw for sheet metal and pulling it out? I'd expect failure but have no better idea.
At least penetrating it with some de-ruster is never wrong.
Nick
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Thanks for the thought - I've tried it! The problem is that the screw tends to expand the pin as you screw it in making it an even tighter fit! And it is a very small pin, so the screw has to be tiny and does allow much pull as the pin is in pretty tight anyway. Why didn't they just put a bloody screw in it in the first place! (Cost I suppose) MIke
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MikeH_QB wrote:

can you hydraulic it out? make tight fitting pin same dia as the id of the pin. fill blind hole with oil, insert pin and belt with appropriate sized hammer. pressure increase will force out the pin (if you are lucky). of course depending on where the hole is and its angle might not work...
Dave
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wrote:

the
blind
way.
it out? I'd

screw
does
I suppose there is no chance of drilling through from the other side and pushing the pin out?
AWEM
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Andrew Mawson wrote:

<snip<
could you use a hollow drill of 1mm ID, bore out around it, then fit a bigger pin to reassemble?
--
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Hack to size. Hammer to fit. Weld to join. Grind to shape. Paint to cover.
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Is it in a situation where you can use a fine tip oxy torch to heat up and either weld on an extension to pull out or soften and crush then pull out ?
--
olmod
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MikeH_QB wrote:

Yes. But now that you have formed a thread, how about retracting the screw a bit so it doesn't expand the pin and then try pulling?
Nick
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Thanks for all the ideas folks! I'll try using some of them over this bank-holiday weekend - its abviously going to be much more fun (spending the time bent double in an arkward space trying to extract the unextractable) than going out and enjoying myself! I'll just ensure there are no children or easily-offended adults within ear-shot when I try! I'll let you know of success or not! regards Mike
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I think a lot of people have not realised the hole down the centre of this is going to be in the region of 0.5mm dia.
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Since this is a roll pin, and therefore presumably hollow, could you hook it out with some kind of puller with a step on the bottom, pushed down the hole?
The other method no-one has mentioned is spark erosion, but unless you happen to know anyone with a spark eroder that would be a major project to make. Might be tricky to get to it in view of the location though.
If none of the other ideas work, try dissolving it out with some dilute sulphuric acid. It should not affect the alloy (assuming it's an aluminium alloy) but test it first. Again, access might be a problem.
Battery strength acid should be about right. If you have to use concentrated sulphuric acid, add about 10% to water (NOT the other way round) slowly, stirring continuously, and wear eye protection.
David
--
David Littlewood

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http://cgi.ebay.co.uk/30-PIECE-DIAMOND-BURR-SET-COATED-DREMEL-OTHERS_W0QQitemZ150152150618QQihZ005QQcategoryZ50383QQcmdZViewItem You might use most/all the set but if the repair is worth more than the six quid or so , maybe worth a try? Probably best in a pillar/pedastal drill for rigidity and feel....
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BTW Mike, further to my previous post, FYI 1mm carbide drills are quite readily available - try an electronics component supplier, they are used for drilling circuit boards (which are very abrasive and wear out steel drills rather quickly).
They do tend to be quite brittle though..... (don't ask how I know that).
David
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David Littlewood wrote:

I wouldn't even try. It will crack after 1/2 a turn. There is a slot in the roll pin!
Nick
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How tiny is it? I managed to remove a few in blind holes, by inserting a small screwdriver, and twisting in whatever direction winds up the pin like a spring. Pulling at the same time moved them a little at a time. Once they were out a bit, the job was finished with pliers. Another was annealed, by connecting one terminal of an old battery charger transformer to the shaft, and a piece of heavy gauge copper wire to the other. The wire was touched to the centre of the roll/spirol pin, an it was soon red hot. Removal was easy at that point!
Steve R.
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Freeze the item
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MikeH_QB wrote:

If you've got a Dremel type tool, beg an old diamond burr from the local dentist, some are less than 1mm diam, and carefully grind it away. Its worked for me.
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make a slide hammer ...and turn the end down to the bore of the pin ... plonk a bit of super glue on it ...and bang away till its out ..
all the best.mark
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