Remove remains of stainless machine screw?

[Jonathan Webb]

Hi,
I had to drill off the head of a chewed-up A4 stainless machine screw, probably M5. This is firmly stuck in an aluminium outboard chassis (20+ years) and there is no head or shank left to grip with anything.

What do suggest?
Many thanks.
J

 

[jordan1]

Is it possible to get some heat on it and try a l/h drill

 

[Rig Pig]

A friend with a milling machine!

 

[WorkshopChris]

Have you seen this post? http://www.mig-welding.co.uk/forum/threads/broken-wheel-bolt.76326/
might be something usfull.

 

[addjunkie]

Heat and a good quality dot punch.

And when you reassemble it use a thread lubricant

 

[Jonathan Webb]

I just came back to edit - heat is not an appealing option as there are plastic parts & wiring nearby which would necessitate a total strip down.

I was looking at extractors etc, will they cope with stainless?

 

[Jonathan Webb]

A friend with a milling machine

Sadly not got one of these. I have got a decent bench drill.

 

[WorkshopChris]

I just came back to edit - heat is not an appealing option as there are plastic parts & wiring nearby which would necessitate a total strip down.

I was looking at extractors etc, will they cope with stainless?

Personally have never had much luck with extractors unless the bolt thread was fine and the head sheared for some other reason.
Oncy you have a hardened extractor stuck your options then get very limited.

 

[brightspark]

any meat left round it to drill out and tap[ a 6mm screw

 

[jordan1]

I just came back to edit - heat is not an appealing option as there are plastic parts & wiring nearby which would necessitate a total strip down.

I was looking at extractors etc, will they cope with stainless?

I have had limited success with extractors, ok if the bolt/screw is not too tight, if they are and you snap the extractor off you have a bigger problem, these are hard.

 

[Rig Pig]

Sadly not got one of these. I have got a decent bench drill.

Then you can clamp it down and drill it, I'd centre pop it and start the hole off with a centre drill, you need to be careful, if the drill kicks off into the aluminium it will be a pain.

 

[The_Yellow_Ardvark]

Build a wall of window putty.

Enough to cover the stuck fixing.

Pour into thee well white vinegar.

Leave.

Warm the casing with a paint stripper.

Leave.

Then grip with an extractor.

If that does not help drill, tap and cry.

 

[indy4x]

I had a bolt shear off in a crownwheel, it was thread locked in place and rather than risk a drill wandering I bought a slot drill for a milling machine, clamped the crownwheel in a pillar drill and drilled it out, heat and an extractor then got it out.

In your case you could do the same but go oversize and helicoil it.

Nice feature with the slot drill is it doesn't wander like a drill bit

 

[grim_d]

I have had limited success with extractors, ok if the bolt/screw is not too tight, if they are and you snap the extractor off you have a bigger problem, these are hard.

I often see people using the course style extractors like dormer and snap on sell, they are rubbish, I see people banging them in with hammers, there's no need. The fine ones as sold, but not made by draper are excellent, I use them all the time up to about 1/4" screws.

http://www.ebay.co.uk/itm/401402484385

Snapping them not a huge problem. Encounter this occasionally at work where I or others have had the misfortune of a broken easy out, a small ball tungsten carbide burr on a high speed or pencil grinder makes short work of the snapped end.

 

[Gwil]

Snapped off stainless in ali a regular marine industry horror. You really need to try and get some heat to it. Trepan it and fit a larger fastening is a nice solution where possible.

 

[jordan1]

If you really want to risk a screw extractor, the best ones I have had success with is Irwin Hanson Multi Spines. I would try all other viable options first.

 

[Jonathan Webb]

Have you seen this post? http://www.mig-welding.co.uk/forum/threads/broken-wheel-bolt.76326/
might be something usfull.

Thanks the Toolstation 2mm cobalt drill worth a try or the milwaukee. I'd been looking at drill places online, with £6 postage...

I can't whack it as it's an thinnish aluminium frame, mainly holding the cowl mounting points.

I wondered if I held a rod against it and heated that, whether that would deliver enough heat? I could get that red hot. That way, I could direct my torch away from everything.

Then you can clamp it down and drill it, I'd centre pop it and start the hole off with a centre drill, you need to be careful, if the drill kicks off into the aluminium it will be a pain.

This is looking favourite, although being an outboard, it's very irregularly shaped - lining the centre up & keeping it there was one reason why I was fishing for other solutions, as well as if it drifts off into the aluminium as you mention, although that's less bad than having a broken hardened extractor stuck in it.

Indy4x Slot drills - new to me. Got me wondering. I had another look at it & it's actually a boss/standoff, raised about 10mm. I might be able to cut a slot in it, perhaps sacrificing a mm or so of boss, which I could epoxy to reinstate the thread if I was concerned - this only holds the cowling, the effort being shared with several other screws per side.

Whatever happens, will try heat. Also worth trying Aardvark's suggestion to dissolve the crud, even if it only does a bit.

A lot of food for thought. Thanks all.

 

[gordon stephenson]

As you know, you don't want the drill wandering off into the ally, Can you clamp a plate with the same size hole to act as a guide?

 

[Kram]

Might be worth trying alum to disolve it. It wont touch aluminium, but takes a day or so. You would need to scratch the stainless surface after getting it wet to prevent oxide reforming.

 

[graffian]

I removed a roll tap with battery acid and a battery charger, the threads in the ali were perfect after doing it.