Broken bolt - tools for the job

[keanej]

I was about to remove the engine mounts and I thought it may be a good idea to paint the brackets - a big mistake, the 1/2 inch bolt broke off on one side snapped off.

So after several attempts to get the broken bolt out ( only making things worse of course ! ) I decided to drill it out.

There aren't any decent tool shops around here any more, so bought some titanium drill bits from B&Q, after around 30 minutes of drilling they had hardly made a dent on the bolt surface.

So off I went to Machine Mart, the chap there assured me these Clarke Cobalt tipped drills are the best thing since sliced bread and would cut through anything - admittedly slightly better they drilled about a millimetre every 30 minutes, concerned about my drill burning out I gave up and searched the web (again) - everything suggested that carbide was the best

http://uk.rs-online.com had some expensive drills made out of carbide, rather than being just tipped - so I took a leap of faith and ordered a couple, they arrived the next morning - They cut through the bolt like it was going through soft butter, so well worth the money. Just goes to show you get what you pay for.

http://uk.rs-online.com/web/search/...=searchProducts&searchTerm=667-3500&x=27&y=15

I have drilled through the bottom of the bolt into the space bellow and filled it up with WD40, I'll leave it soaking overnight. The question now being having got a nice 5mm hole through the middle of the bolt do I use a stud extractor or drill it out further and retap the hole ? - I'll sleep on that one.

 

[colnerov]

Hi, Rule of thumb here is if it broke going in Yes, if it breaks coming out No. You will only break easy out in the bolt
and then be in a bigger pickle. Just drill out to the bottom of the threads and then hopefully pull the remains out.
If not drill out further and retap 3/8 UNC.

 

[rockdemon]

I was surprised how difficult it was to get left handed bits given my recent exploits with the snapped manifold bolt.... Only place i could find them was on amazon of all places!

Rich.

 

[quattro]

I had to drill some 10mm holes through 12mm steel when the brackets for my chassis spinner were the wrong length.

I also had the drill out the brackets for the front brackets which were 9mm, out to 10mm.

My normal drill bits would grab and shatter, So I bought a 10mm cobalt bit and used some cutting oil.

Did a perfect job - just right.

Richard