Snapped bolts and buggered threads

[Horza]

How often do you go to start a job on the van only to find some bodger has previously been there and buggered it up in advance?

I have just been out to fit a new ruber bonded exhaust mount, an easy job in theory, and found the dirty great footprints of a previous owner all over it.

The main problem are the bolts holdong the whole shebang to the sump. It's a diesel van so I have the huge angular thing going on. There should have been three bolts but there were only two because one hole in the sump has had the thread almost completly ripped out already. One of the remaining two snapped off when I tried to budge it (I hardly touched it and suspect metal fatigue due to it not actually being tight to the vibrating bracket).

I have had to botch the whole thing back together just to give me a working van but I need to fix it.

What do I do? Something to do with drilling and helicoils springs to mind but I'm just not experienced in this type of thing. I'm scared that I might make a not good hole in my sump!!

[Tex Ritter]

If as you say the thread is still there but damaged to bu++ery, clean out and tap the hole using a second taper and/or a plug tap, to the next size up, It will be a coarse thread as It will be into soft material.

Drill out and remove the remains of the snapped bolt in the sump casing (you may have to flatten the stump to ensure an accurate first drilled hole), take your time, centre pop it, and make sure your first hole is drilled bang in the centre. Enlarge the hole enough to enable a strong easy-out to remove the remnants.

Tex R

[Horza]

Right, on inspection of the bits left over I think the origional bolts would be M8 (scraping the rust off the bolt head reveals at least one 8, it's a 13mm head and the diameter of the crushed thread is just a tad over 7mm).

So if I go to M9 Coarse with a suitable tap I should be laughing? Should it be a taper tap? Wont the bolt tighten up too quick to hold the bracket? I wont have to drill into the sump for the knackered thread then?

What's an easy out?

I think I can see what happened as dissembly leaves you with two course thread bolts, two fine thread bolts the same length and head size and one long bolt with nut. Silly so and so has put them all back in in the wrong holes.

My Exhaust is now held on with a bit of wire, I don't think it's going to pass the MOT like that

[Tex Ritter]

When you drill and tap an ordinary hole you have three taps available:

The first taper, second taper and finally a plug tap. In your case you will not be able to use the first taper, or possibly the second (unless you grind off part of the taper length) on the damaged threads, therefore you'll have to rely on being able to use the plug tap to clean up the existing hole.

If done carefully, you can drill and tap to a larger size without 'going through' the sump.

As it's aluminium you should get away with using the plug tap to cut the new thread.

An 'easy out' is a broken stud extractor device used to insert into the hole you have drilled into the remains of the stud, it has a left hand twist to it, so in theory the harder you twist the tighter it should grip on the shoulder of the drilled hole.

In my experience, the parralel extractors are the best for this job, but if you only have the screw type, and the hole is large enough, then they should suffice.

Tex R

[Grun]

Euan,
Go to www.screwfix.com and search for screw extractor set the part number is 18643 These are commonly known as 'Easy outs'
The link is sooooo long and I do not know how to shorten it to 'here' like the clever clogs do!!!
There is a photo to give you the basic idea. They have a left hand spiral which bites into the stud you are attempting to remove.
Halfrauds sell them, stud extractors is another name for them.
Mike

[Horza]

Many thanks folks.

I thought I had a doobry for doing that but I can't find it now, it had tapered and parralel reverse threads on it and I always wondered what it did. Not as scary looking as those things on Screwfix though.

The hardware man says not a chance on M9 so I have to go to M10. He sounded right dower on the phone but reasuringly old and knowledgable. Hopefully he'll be able to kit me out at lunch time and I guess I'll be under the van in the dark tonight to get it done.

[Horza]

Grrrr.

Those easy outs are neither easy nor is the stud out. If they were really branded like that I would have a trade descriptions claim. I drilled out the remains to 8mm and tapped it, serves the flippin thing right.

Job's a goodun though, thanks again Tex and Grun

[dingleyhythe]

Easy outs are the spawn of the devil - they almost never work and they are more work to use than drilling and tapping.

They fail for loads of reasons:

They expand the stud so it grips harder

The taper on them means they only grip a tiny bit of the stud

cheap one are brittle so they crack

Worst thing of all is if they break in the stud - they are so hard you cannot drill them out - only answer is usually a spark eroder or sometimes a chisel!