Drilling out screws - tips needed

[Tempest 0]

OK, folks, need an authorative Idiot's guide to how to drill out screws.

 

Was doing a little job on the C today, and yup, rust had done its thing to a cross-head screw, which I nicely rounded off.

 

Out came the drill, started with a 2 mm or so HSS drill bit, but as usual despite what drill size I use or start / end with, I never seem to be able to get any further than the head, not able to get into the actual thread.

 

Question time:

 

How do you guys do this?

 

What speed do you set your drill to ?

How long does it take (yes, dependent on screw size, but still would be helpful)?

How much pressure do you apply?

What size drill bit do you use to start with, do you end with a different drill bit size?

What material drill bit do you actually use (HSS or diamond, can't afford the latter :lol:)?

 

 

Are the threads on screws typically hardened, or why do I get through the head so easily but not the thread?

 

Thanks for some useful tips :-)

 

Tempest

[A1 VR6 0]

Hi Eric, try an impact driver first or use a hack saw to open up one of the slots after spraying with plus gas or something like it. Drilling should be the last resort.

[CorradoVR6-Turbo 0]

What are you drilling out?

 

A1 VR6, is that pic your sig?

[tonedef 9]

I use some really tricky left hand fluted (run in reverse) cobalt drill bits bought from the Snap On man. They come in a kit with broken screw extractors, cost an absolute fortune but are really worth the investment when part way through drilling (nice and steady) the screw comes out on the drill. :D

[-Neil- 0]

Take a look at these....

 

http://www.machinemart.co.uk/product.asp?p=040219960

 

http://www.machinemart.co.uk/product.asp?p=060220180

 

http://www.machinemart.co.uk/product.asp?p=060220181

[Critical_Mass 10]

Yeah get a flat head screw driver and a large hammer and try to make the cross shape open up a bit. Then get a LARGE cross head screw driver and put as much pressure on as poss and turn slowly. May sound crazy but sometimes tightening the screw can make it a bit easier when you come to loosen it.

[Supercharged 2]

Eric - they do a small version of the bolt grippers at machine mart - perfect for screws as long as you can get a socket round them, also may have to file slightly to fit the socket...

[Tempest 0]

Right thanks for the tips so far.

 

I was trying to undo the screw holding the airduct for the right front brakes to the bumper. As this screw is recessed (lower bumper grille also in the way), and I left the bumper on the Corrado (mine's a swine to get back on again, thanks to a bit of a bodge job by previous owners, a few lighting cables too short, long story ...) hacksaws didn't work (can't get the blade in there), didn't get anywhere with hammering a flatblade in either, as the screw was that tight.

 

Lying underneath the C like that, with the C on axle stands, you can't really use an impact driver on that screw, tried, but awkward to exert force onto the screw with me lying on the floor, let alone strike the hammer nice and forcefully.

 

I've never had any success with these so-called screw extractor bits, as again the ones I have seem not hard enough to eat their way into a potentially hardened screw thread. In my attempts they always just eat in a bit (mainly the head), then start just rotating on the spot, destroying what they had done so far.

 

Mind you, the Snap On ones sound interesting, as from what I understand they seem to be harder than the screw material itself. That or more expensive (titanium or diamond) drill bits, I guess ...

 

So ultimately I resorted to good old brute force, chisseled the Barsteward out :lol:

 

Off to VAG tomorrow to get a new outside temp-sensor, as that's the reason why I did this, as I don't get a proper readng on my MFA (tested the MFA with a Pot, and all's fine, sensor no reading however, so knackered - at least that part was all nice and simple).

 

Tempest

[tonedef 9]

Tempest These are the ones I have, left hand drill bits and extractors. As I wrote before, best thing is when the drill actually gets the screw/bolt out although it doesn't happen every time. Sometimes you have to use the extractors too.

 

Mine didn't cost quite so much but I had to wait for them to be on offer.

 

Tony

 

http://buy1.snapon.com/catalog/item.asp?P65=&tool=all&item_ID=10418&group_ID=1254&store=uk&dir=catalog