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Cherub Chat => Tech Chat => Topic started by: daryl_wilkinson on March 31, 2010, 06:56:38 PM

Title: screw extraction?
Post by: daryl_wilkinson on March 31, 2010, 06:56:38 PM

Somehow when tightening down a kite halyard turning block with a clutched drill driver the stainless pan head parted company with the screw. The other one was fine with the same clutch setting. I have just got some screw extractors and was just about to attempt to remove said screw ( 6 gauge ) and I thought I'd ask if anyone had any tips for centering the drill bit on the screw shaft. It's not really something you can center punch. I was thinking of drilling through a bit of wood and holding that down over the screw to maximize my chances of staying true, but it will make it total guess work as to whether I am on target or not? Any ideas? I think I shall rename my boat - "LUCKY" as some ironic statement.

Title: Re: screw extraction?
Post by: roland_trim on March 31, 2010, 07:35:15 PM

I got scared of them ans dremmel'ed a new head on the last one I sheared?

Taking the same approach you could dremmel a divot?

Good luck

Title: Re: screw extraction?
Post by: Tim Noyce on April 01, 2010, 09:07:58 AM

This used to happen a fair bit with cheap stainless screws when I worked at the boat builders. I always found that grabbing the exposed end with a pair of Maul Grips and carefully turning it back out was the easiest way to get them out. This obviously relies on having enough exposed screw to grab though.

Never tried the extractors though Daryl. Sorry.

Title: Re: screw extraction?
Post by: ross_burkin on April 01, 2010, 11:22:08 AM

If you drill it, don't forget that it will get hot!

Title: Re: screw extraction?
Post by: Phil Alderson on April 01, 2010, 12:44:03 PM

I have used screw extractors before, although normally on a larger size. We would normally centerpunch before drilling.

Rolands suggestion of using a dremmel to create a divot is a good one, you can also use it to flatten off the top if it has sheared at an angle.

The screw extractors are brittle and easy to break, getting the correct depth of hole is quite important.

Title: Re: screw extraction?
Post by: JimC on April 02, 2010, 07:39:31 AM

Quote from: Phil Alderson on April 01, 2010, 12:44:03 PM

The screw extractors are brittle and easy to break, getting the correct depth of hole is quite important.

I'd go as far as saying exceedingly easy to break. And then you have a lump of non-stainless steel stuck in the screw.

The act of using them tends to expend the remnants of the screw which makes them grip tighter. Obviously there is a knack and skill to using the things which I don't possess. On the other hand its got to be much easier to get a stuck screws out of a new composite structure than in getting corroded plain steel out of an alloy substrate, which is where my failures occurred.

Gently filing the remnants of the screw flat so you can centrepunch and drill more accurately has to be a good thing. An even better thing would be to have someone who's done it successfully before involved in the operation...

I concur with Tim about mole grips: knowing that I am incompetent with easy outs I would slice back the surrounding structure so I had enough screw to get a really good grip, then repair later rather than risk getting the carbon steel stuck in there.

Title: Re: screw extraction?
Post by: daryl_wilkinson on April 02, 2010, 10:20:23 AM

Thanks for tips and advice..... here goes nothing, I'll let you know how it went!

Title: Re: screw extraction?
Post by: daryl_wilkinson on April 02, 2010, 07:27:33 PM

Success.
Just started with a 1mm drill and went up a drill bit at a time from there. Came out a dream with extractor.

Anyone know where to get 'Tuffnell' plate from?

edit: found it, it would help if I had the spelling right!.... 'Tufnol'!

http://www.directplasticsonline.co.uk/TufnolSheet/