How much trouble can one bolt be?

[Deadeye]

Well, quite a lot as it turns out.
One stuck bolt currently stands between me and I think quite a good rescue of a badly rusted up thicknesser.
It's a slotted machine screw for setting blade height in the cutter block. Two of its peers came out relatively easily, the third put up a hell of a fight but succumbed following Trevanion's advice. The final one is beating me.
I've tried all manner of combinations of soaking in penetrating oil, heating the block and freezingn the bolt, tapping it sharply to break the bond, soaking in citrate, trying to tighten before loosening, and speaking to it sternly, all to no avail. I also enhanced the slot with a dremel and diamond wheel as it was getting rounded by my failures - any more force will shear the screwdriver or the bolt I think!

Any final ideas before I try to accurately drill out a hardened bolt from an off-centre position on a circular block? They're 1/4" and only in about 3/8ths, but rotted solidly in place.

If I do have to drill it out, I was hoping to start small and only go up to the inner diameter so I can scrape out the thread and reuse. Is this remotely feasible?

 

[Trevanion]

A traditional impact driver can sometimes break things loose that you simply cannot do with a regular screwdriver.

Have you tried threading it in a bit at all? Sometimes they can thread in further firstly without too much issue and then they thread out easier.

 

[DBT85]

How long have you left it to soak in penetrant? I've heard people talk about leaving some things for weeks with a daily top up to help it along.

 

[Torx]

Lots of cycles of heating / rapid cooling with a squirt of WD-40 then get it hot and touch a candle to it so the wax is drawn in via capillary action.

 

[guineafowl21]

A traditional impact driver can sometimes break things loose that you simply cannot do with a regular screwdriver.

Have you tried threading it in a bit at all? Sometimes they can thread in further firstly without too much issue and then they thread out easier.

A decent impact screwdriver with exactly the right bit can work magic. The impact drives the bit into the screw head, reducing cam-out, and the rotary shock breaks it free. Think of trying to chop a mortice by pushing the chisel into the wood, versus shocking it with a hammer.

Using a punch to tap the screw round can be surprisingly effective, too.

 

[Inspector]

A 50/50 mix of Acetone and ATF (automatic transmission fluid) if reputed to be light years better than WD-40.

As for the last ditch drilling out of the bolt. Don't. Buy small carbide rotary files (ball or rosebud shaped) and grind off the head. You have better control and can correct if you find you are drifting off a little. I have used them to grind out broken Easy-Out screw extractors from #8 and #10 (3mm or 4mm) screws and then cut down through the centre until I could pick out the thread with a dental pick. Once you get the head off it should come out with vice grips.

Pete

 

[Trevanion]

Just for clarification, what Deadeye is trying to remove is the slotted knife adjustment screws in the cutter block, you can see them behind the knife inset into the cutter block on each end on mine here:

 

[jimmy_s]

Is the block off the machine? - could you arrange for electrolytic rust removal? - if so I would give that some consideration. My father had an old iron lock that he'd found - it was completely caked in rust. Out of curiosity we cleaned it using electrolysis and to my amazement it cleared the rust out of the innards and the thing could actually turn.
Based on that experience, I would consider giving it a go to see if it would remove the corrosion.
Another option that can be useful is to weld a nut to the offending item, obviously the screw is then knackered but the combination of heat from welding and the improved grip that you can get from a nut with a socket often does the trick, but in this case its probably not possible as it sounds like the fastener is a small countersunk setscrew?

 

[HappyHacker]

I support Inspector's recommendation not to try to drill it out, not that it won't work but it can get messy when the first drill goes in off centre. DAMHIKT.

I would support trying electrolysis. I have used it to get rid of rust on quite a few things successfully but not something internal, but it is cheap, easy and non destructive so what have you to loose?

Good luck

 

[Eric The Viking]

Have a look at Adam Booth's YouTube channel ("abom79"). He is a very patient expert machinist, with an enthusiasm for traditional work, and who works to tight tolerances. He regularly removes "impossibly stuck" threaded objects from holes, and keeps the remains as trophies too.

Take-homes for me on this:

1. drill as an absolute last resort (you know this already!)
2. he usually uses far more heat (oxy-acetyline) than I have available, and is far more agressive with it, or so it seems.
3. he sometimes has failures but usually gets there in the end.
4. if you drill, use a left handed set, never the ornery sort. I think this is why some of my attempts have failed in the past.
5. His best screw extractors are a different design to the cheap set I have.
6. He is exremely patient, e.g. feeding it Plus Gas (or whatever) over days rather than hours.

There is one video where he salvages a large vintage carburettor block that I thought would just be scrap, and others where welding a nut on top solved it, and so on.

I used YT's search: "stuck bolt Abom79" to get quite a long list of his bolt-removal videos. Anything with "SNS" (Saturday Night Special) in the title will include several topics and probably a lot of chat, so skip through to find the relevant part. He also shows his failures, which is both reassuring and helpful.


Hope that is useful.

E.

 

[guineafowl21]

...but usually gets there in the end...

This is what I have found, working on rusty cars. I just work away, trying a variety of techniques, and usually find the fastener just gives up at some point. A satisfying moment.

A few more tips:
1. Using a large punch and hammer, strike the screw square on a few times.
2. Next try an impact screwdriver. Try alternating directions a bit.
3. Failing that, use a small punch to shock the screw round.
4. It looks like too much mass around the screw for spot heating to be effective, but putting the whole part in and out of the oven for thermal cycles might help.
5. Drill as a last resort, but start with a small bit. Once you’ve taken out the centre (or thereabouts!) of a screw, other techniques might then work.

You can see from above it’s about impacts, not steady torque.

For what it’s worth, use plenty of your favourite penetrating oil. I find none of them are any particular use until you get the fastener to move, even a tiny bit. Then, alternating directions will work the stuff into the threads.

There are any number of oils out there, special recipes, etc, and an equal number of stanch advocates. Rather like a disease where there are many possible treatments, it suggests that none of them are properly effective.

I have made blu-tack ponds around bolts, and soaked for days, then finally removed the thing to find the threads as dry as... well, a very dry thing

Persistence is the key, and try not to lose your rag!

 

[Bod]

You are using a proper penerating oil, rather than the likes of WD40?

Plus-gas is the industry standard go to penerating oil, but even this may need days to really get in.
When using an impact driver with a hammer, twist the driver in the direction you want to turn, keeping that pressure up during the hit, which can be surprisingly hard.
What corrosion is evident on other parts already removed?
If this is mechanical seizing, then replacing the other screws may even the pressure, allowing the difficult one to be moved .

Bod.

 

[NickM]

If you have to drill it out and damage the thread in the process, you should be able to repair that with a helicoil if need be. They're not a bodge. In fact, it's quite common for engine builders to replace threads in alloy blocks with helicoils as standard because they are stronger. I've used them on cars a few times and they're reasonably easy to do. The kits come with the right size drill bit and tap to make the thread.

 

[Eric The Viking]

Reminded me: I have a bike with stainless exhaust system, into which some numpty* put mild steel Allen bolts. These "exploded" with rust where they were in contact with the cans, and were impossible to get out. I found a local firm that does spark erosion - cost me 50 quid for four threads (M6, IIRC), which was way better than the hundreds new silencers would have cost me. The threads were re-usable, and using stainless bolts for reassembly elegantly transferred the rust problem to the mounting lugs instead (<grrr!>).

Last resort but the results ought to be excellent.

E.

*surprisingly, it wasn't me.

 

[Richard_C]

I've had some success on rusty car bits with percussion. Put releasing fluid in, not sure WD40 helps much, and give the component, not the screw, some sharp repeated hammer blows for a minute or so. I got a seized locating screw out of a neighbours brake drum recently by doing that and getting the drum to "ring". I suspect the resonance helps the fluid to get in and the threads to shake loose. It's free, not destructive as long as you don't whack it too hard, and worth a go when other things fail. I'm assuming the component is sturdy stuff.

 

[Seiken]

+1 for the impact driver, I've moved a few seized screws on cars with one of these. As it's a fair mass you're hitting I use a club hammer to hit it.

 

[Racers]

Proper penatrating oil, heat, and impact driver time is all you need.
Put some oil in heat it with a torch then the next day do the same then next day then the next day, give it a twist every now and then it should start moving.

Pete

 

[Housey210]

is the blade clamp out?

 

[Phil Pascoe]

Two years later, if it isn't it's well and truly stuck.

 

[Deadeye]

Two years later, if it isn't it's well and truly stuck.

Lol. It's out and the machine is in use!