Bummer - Stripped thread

[schlitzaugen]

I think there may be some confusion about Ezyouts. I have encountered two types. The first is the left hand thread variety that must be screwed into the centred and drilled hole which I have used with much success after liberal applications of CRC or WD40. The other sort is marketed by F H Prager and has a very coarse slightly left hand inclined thread. This one is designed to be hammered in. I would not use these in a fit. (Sheer butchery).

I don't think there is any confusion.

There is however a third type I have seen (and there might be others, who knows?). This one has a square shank with sharp straight cutting edges that bite into the pilot hole you have to drill (this is similar to the torx idea only it has proper sharp edges designed for the job). There is then the left hand tapping technique as well as the left hand drill technique mentioned above. They just don't work. If you have an easy job where the only problem is that the screw has sheared off but otherwise is not stuck in, yes, they might work. Exhaust studs are not the worst I have seen. Soaking patiently over a few days with WD40 usually gets them out.

Most of us here had to deal with screws well and truly stuck beyond hope (think head bolts sheared off flush with the block). You're not going to get that out with the mother of all easy outs. The only way to do it is to drill and hope. Sometimes even that doesn't work but in time you improve your success rate with practice.

 

[Gone]

http://www.mytoolstore.com/hanson/hanson.html
Left Hand Heavy Duty, Surface Treated, Jobbers Length High Speed Steel Fractional Drill Bits

Tip: If you use a left-hand bit to drill the hole in a broken screw or bolt so you can extract it, the odds are good that the very act of drilling will remove the broken screw without ever needing to use the extractor. Your drill must be running in reverse when you use left-hand bits.

Edit: sorry guys, that was a direct quote from the above site. Fixed now.

I have attempted on occasions to grind the tip of a bit so that the twisting force it imparts to the remnant bolt is in the "undo" direction. I've had some success with this method but I think I was just lucky.

 

[bluey504]

Left hand drill bits do work wonders, even got 12.8 grade cap screws out! Showed a contractor with decades more experience didn't believe me until I did it in minutes using a lefty drill and a parallel ezy-out.
Make sure that the remaining stub is ground flat and soak with a lubricate, Inox is my current preferred potion, and get your centre punch exactly right and 'smote it with force'. Then add liberal swear words and take your time and it should all be good, if it doesn't work put it down to experience and 'Get a Man in.'

 

[schlitzaugen]

Left hand drill bits do work wonders, even got 12.8 grade cap screws out! Showed a contractor with decades more experience didn't believe me until I did it in minutes using a lefty drill and a parallel ezy-out.
Make sure that the remaining stub is ground flat and soak with a lubricate, Inox is my current preferred potion, and get your centre punch exactly right and 'smote it with force'. Then add liberal swear words and take your time and it should all be good, if it doesn't work put it down to experience and 'Get a Man in.'

This is closest to my own experience.

 

[UFO]

I too am a long time convert to Inox and Lannox, but have recently discovered the worth of Penetrene and Nut Cracker, both specifically for getting into rusty/stuck threads.

 

[Roger Wilkinson]

Two pieces of advice, Joel.

1. It's not a stripped thread, it is a sheared capscrew or stud.

2. Use more time for penetrant to soak in and less force. Patience is a virtue. Anything you have to hammer in will expand the threaded part and make removal more difficult. The harder you hammer, the more difficult. Go easy.

Roger

 

[Haakon]

Meh. Ignore it. It has five left to hold it down.

 

[PeterT]

removing broken taps - nitric acid

 

[robmac]

removing broken taps - nitric acid

These are faster for broken taps:

http://www.metal-disintegrators.com/

Or this http://www.machineryhouse.com.au/T001 only 3.5k.

One of my employers had a smaller, portable version.

It was well used. Due to heavy handed staff members.

Spark eroding is very fast and precise, good for making holes too

 

[STALLED]

Thanks for the further advice! There is still some thread popping out of the rocker cover, so some WD40 and patience will probably get the bastard out!

Thing is, I was gentle with the screw to start with, as i'm usually fairly paranoid about breaking things around the head! Ah well!

 

[James504]

Meh. Ignore it. It has five left to hold it down.

The best advice so far.

 

[Gone]

Two pieces of advice, Joel.

1. It's not a stripped thread, it is a sheared capscrew or stud.

2. Use more time for penetrant to soak in and less force. Patience is a virtue. Anything you have to hammer in will expand the threaded part and make removal more difficult. The harder you hammer, the more difficult. Go easy.

Roger

Thanks Roger, it needed clarification.

I forgot to mention: if there's a remnant of potruding thread left on the sheared capscrew (bolt) you may, after soaking it with the penetrating solution of choice, be able to gently tap it around with a fine punch and hammer.

 

[PeterT]

Anything you have to hammer in will expand the threaded part and make removal more difficult. The harder you hammer, the more difficult.

Now this is where we can really start to have a discussion. If the threads of the mating parts are already touching, and assuming 75% thread, the remaining 25% is probably filled up with corrosion, meaning the metal can't expand outwards. If you do drill a hole and belt in a torx bit, theoretically the metal should flow around the torx bit and into the drilled hole. However, the metal is no longer ductile, having gone well beyond yield, UTS and finally breaking point from the attempted removal process. So, the question is, what will happen?

 

[Roger Wilkinson]

Now this is where we can really start to have a discussion. If the threads of the mating parts are already touching, and assuming 75% thread, the remaining 25% is probably filled up with corrosion, meaning the metal can't expand outwards. If you do drill a hole and belt in a torx bit, theoretically the metal should flow around the torx bit and into the drilled hole. However, the metal is no longer ductile, having gone well beyond yield, UTS and finally breaking point from the attempted removal process. So, the question is, what will happen?

Good points, Peter.

I think it depends on the material of the fastener, the material it is screwed into, the hardness of each, the age of each, the proportion of thread in each part, the degree of corrosion, the amount of handling each part has already had, and whatever else I have missed. Hammering in the torx bit will not only force the metal to move laterally, it will also push it downward, further into the hole (to the extent it can move in its now-hardened state). If there is nowhere for the metal to go in a blind hole (or at the end of the hole drilled within the fastener) then I think it is likely to move outwards. Even drilling the pilot hole (or holes) will work-harden the fastener.

All our theories are great, but they seem to me to work best on new materials. Anything old, corroded, work-hardened and otherwise manky will not behave as politely as the equations say. Sometimes drilling it out is the best way.

There are a couple of other options we haven't discussed much. Hammering has been mentioned a little, and I find shocks a handy tool, as long as you don't deform the part too much. If there is a bit of thread protruding, you might be able to screw on a nut, which gives you something to hold a flat punch against so you can give it a gentle whack with a hammer.

Another option is the "hot spanner". Applying gentle heat forces expansion of the parts, and contraction when they cool. This can be enough to free corroded fasteners. Applying penetrant when the parts are cooling down sometimes helps. It makes a lot of smoke and hissing noises, too, which at least makes you feel as though you are achieving something. You do have to make sure you don't do any collateral damage to neighbouring parts. Heat is my favourite tool for removing fasteners. I don't bother with those namby-pamby little tin cans of gas, I go straight to the oxy set. If necessary, I use the smallest tip, the lowest pressure and the smallest flame I can maintain.

Related to heat is welding. If the broken piece of thread is large enough in diameter, and flush with the surface or slightly proud, you can drill a hole in a small piece of flat steel, place it over the thread, and weld the two together. If you get it right, you can often use the piece of steel as a lever to screw the thread out.

These techniques may not be entirely relevant to the present situation, but others may well find this thread and I think it is good to canvass a range of options.

Roger

 

[cme2c]

Good points, Peter.


These techniques may not be entirely relevant to the present situation, but others may well find this thread and I think it is good to canvass a range of options.

Roger

Thanks, Roger, I happen to have a situation where these thoughts come in useful. Fortunately, I can get to the back of the hole and use a RH drill!

In the spectacle industry a tool is available that has a pattern similar to a countersink tool, only flattened, This will grab the end of a broken screw and let you unscrew it. Mind you, we are dealing with screws of 0.8mm to 1.6mm.

John

 

[Whippet]

Concur

In most cases I would use and easy out your doomed to failure from the start. The reason the bolt sheered in the first place is the threads are rusted or seized for some reason (eg: salty soggy pommy car). So by drilling out and using an ezyout you trying to unscrew the bolt with something that has less strength than the original bolt you sheered would have had. Add to that the fact the ezyout tends to "expand" the hole freezing the thread even more solidly.

Ezy outs will work where a stud or bolt has been over-tighten and sheered, however I've never had sucess where the bolts threads were initially the cause of the problem.

Hey Joel, what's wrong with a cable tie to hold it all together .... It is only a Xantia clone with bouncy springs after all

I like the torx idea as all you would be likely to do if it fails is strip the edges from the torx driver rather than sheer it off in the hole.

seeya,
Shane L.

I strongly agree with Shane, there is a reason the full shank bolt sheared in the first place, seems the thread has corroded. I would use an oxy accetelyene torch and heat the remining shank to red, then let it cool. When cold, spray some WD40 etc, and give it a tap to hopefully fracture the corrosion; then use whatever, maybe lock on multigrips, and it will hopefully unscrew.

In my apprenticeship days I too have used and broken many easy-outs, for similar reasons articulated above. I really like the idea of the Trox, and the splines will have a larger contact area and less point contact, therefore a greater possibility to tranfer torque without breaking.

 

[cme2c]

This is the job I was talking about earlier. When I got this hinge it had surface rust, and there was a broken bolt in the centre hole. The careful drilling and tap method worked a treat! I ran the tap through the other threads to remove excess paint, as well. Thanks, guys!